Nov. 17, 2021

027 - Travelling fires with Guillermo Rein

027 - Travelling fires with Guillermo Rein

If you have ever learned about the compartment fire dynamics framework, have tried zone modelling or any kind of fire modelling, you have probably noticed that as the compartments get bigger, the less uniform conditions inside are. At some size, the flashover or a "single-zone" model theories just break, MQH equation does not give a reasonable solution and the fire seems not capable of growing to a huge size... But yet, they destroy buildings. Local fire exposure may be damaging to structural elements in the same way as a flashover is. And that is how we considered it for many years...

But there was a gap. Something between a localized fire and a flashover'd fire. For many years we've seen it, but we have not acknowledged it fully untill it was given a name - the Travelling Fire. In today's episode, I have invited prof. Guillermo Rein of Imperial College London, to tell us the origin story, recent developments and future plans related to this methodology. This should be interesting to all - from fire scientists to engineers.  IMHO, a well invested hour of your time!

Make sure to connect with Guillermo on socials:
- Twitter
- LinkedIn
and with his group - Imperial Hazelab (also on Twitter).

Guillermo has published 200 research papers, and among them many landmark pieces on travelling fires that I recommend:

and some many more... You may also be interested in the relevant PhD thesis:
- Jamie Stern-Gottfried (2011)
- Egle Rackauskaite (2017)

And some other work related to travelling fires carried across the world:


[00:00:00] Wojciech Wegrzynski: Hello and welcome to Fire Science Show session 27. Great to have you here again. Before we jump into the episode, I wanted to reach out to all of you supporting Fire Science Show, and I'm really grateful for your support. And if you would like to support me and podcast you can do it in multiple waves.

[00:00:16] Wojciech Wegrzynski: And, two of them are by simply referring this show to your friends and colleagues. Uh, word of mouth is still number one way for podcasts to get shared. And, maybe your colleagues don't know they have a podcast app in their phone. Maybe you have to just steal the phone and put the Fire Science Show name in it and play it to them.

[00:00:35] Wojciech Wegrzynski: So they finally joined us in here. Ah, maybe don't be that brutal, but I would really appreciate if you helped me spreading the word about the podcast, because the more people listening, the more people we can help and have more people with us on this journey, into the fire science.

[00:00:50] Wojciech Wegrzynski: And, also I really appreciate the donations. You can donate to the podcast through the podcast website. There's buy me coffee button, where you can drop a few euros to the [00:01:00] show. All of the donations go to supporting the podcast, paying for my, hosting mastering, uh, editing software and so on. So on. So if you would like to support me in this way, I would appreciate that. And anyway, I really appreciate you being here and listening to the show because I'm doing it for you. And I'm really happy that you are here with me.

[00:01:21] Wojciech Wegrzynski: So for the happy that today, and it's actually a comeback to the podcast, I'm hosting again, professor Guillermo Rein from Imperial college, London, Guillermo was my first guest in the podcast that I've ever interviewed. And we've talked about peat fires. And today we're going to talk again about fires this time fires in buildings and a very particular type of fire, which is called the traveling fire.

[00:01:45] Wojciech Wegrzynski: So first, let me introduce you to the traveling fires. There is a thing in the fire science that's called the compartment fire dynamics or the compartment fire theory. It was pioneered by Kawagoe and Thomas, then written in handbooks by Drysdale, [00:02:00] Quintiere, Karlsson and it's something that we are being taught, learning, fire science in our universities. The theory is about how fire grows in compartments and how the physics dictates the size of the fire, how it can go into either fuel control or ventilation control, what's the maximum size of it and so on and so on.

[00:02:21] Wojciech Wegrzynski: But there is a very profound limitation to this theory and it's related to the size of the compartment because. The method assumes that the temperatures in upper smoke layer or in the compartment as a whole are more or less unified. And once you have a large compartment and the fire is localized, it does not cover the whole compartment then you start having gradients of temperatures. The dare theory breaks down in a bit For many years, it was not considered as a big issue because we commonly assumed that flashovered the fire in small compartment where you have the maximum temperatures is the absolutely worst case scenario you could have in the building.

[00:02:57] Wojciech Wegrzynski: But after fires, such as World Trade Center, [00:03:00] disaster. This was in a way revisited and it is found it's not necessarily always the worst scenario. And sometimes if the fire takes a long time to travel through the compartment, burning it part by part, it can lead to much worse outcomes than a short and very hot fire in a flashover setting.

[00:03:21] Wojciech Wegrzynski: And this was pretty much the basis for emergence of the traveling fire, methodology methodology in which the source of the fire is not considered a stationary. Instead You can see the two edges of the fire moving through the compartment, the leading edge. So the edge at which the fire ignites new fuel and the burnout edge or the trailing edge where the fuel burns out.

[00:03:45] Wojciech Wegrzynski: And there's no more fire at the location. And as these two edges move through the, compartment fires is obviously in between them and in a way it travels to the building. And, this is a very powerful concept. That's a missing link between [00:04:00] the localized fire theory and the flashovered fire theory. And yeah, in this episode, we're going to talk a lot more about how this came to life.

[00:04:09] Wojciech Wegrzynski: What were the assumptions of its creators and how it's being developed today? So, uh, I hope you are going to wildly enjoy this one. I really enjoyed having Guillermo again in my studio. So yeah, let's not prolong this anymore. That's been the intro and jumping to the episode

[00:04:46] Wojciech Wegrzynski: hello. Welcome to Fire Science Show. I am today with professor Guillermo Rein again. Hey, Guillermo. Great to have you back to the show.

[00:04:53] Guillermo Rein: Hey, thanks for having me again. You're awesome.

[00:04:56] Wojciech Wegrzynski: Just few months, but it feels like a whole, I don't know. Decade [00:05:00] has been since last time we've spoken.

[00:05:02] Guillermo Rein: Well, I hear you every week.

[00:05:04] Wojciech Wegrzynski: Oh, that's nice. Thank you, man. I hope you enjoy it.

[00:05:08] Guillermo Rein: Yeah, it is. This awesome is unique and it's very refreshing and you are making the point that something like this, this podcast was needed. So you are making our field better and larger. Thank you. We need a statue for you..

[00:05:23] Wojciech Wegrzynski: Nice. Thank you. Thank you so much. It's going to be a very fat statue. I would not recommend that. Let's talk about some traveling and it's going to be traveling fires. I'm really happy to see so much happening around on this round is important subject, including, the recent publication of, of your team led by Dr. Rackauskaite that summarized one of the biggest or the biggest experiment we've done actually together on this subject. And, I see some interesting things happening in France. I have my own memories of interesting things that happened in Poland. And I guess it's the time to, share this a bit with, [00:06:00] uh, the listeners. What do you think about this subject? Is it, something that's really fires you up?

[00:06:05] Guillermo Rein: This is one of the contributions that we had to the field that I liked the most. This is very close to my heart. Literally not just the physical heart, but the professional heart. This is something that I started a long time ago when I was just freshly arrived to the university of Edinburgh.

[00:06:22] Guillermo Rein: The core of the ideas were developed at Edinburgh and then the applications and the subsequent improvements and developments where we're done at Imperial. And we continue doing them. This is a topic that we haven't finished with, not just us. there is a still a lot to do on the topic?

[00:06:40] Wojciech Wegrzynski: Maybe you can take me back in time to your early days in Edinburgh, where this was born. And, tell me what, made you pursue a completely new methodology to define boundary conditions for structural fire engineering? Didn't you like the standard fire curve enough?

[00:06:55] Guillermo Rein: No, no, I like it, but not enough. it is important. We are talking about traveling [00:07:00] fires. This is a concept that we developed in 2006. I think it was the first. Actually the first time we develop it, it didn't have a name. So it was not travelling fires. It was lifted on name, traveling fires.

[00:07:11] Guillermo Rein: He was Barbara Lane from Arup who in an, email exchange, said those travelling fires of yours, Guillermo. I thought that's a brilliant name. Let's call it a travelling fire. So the next paper is then they use struggling fires as a name, and now it has catch. And it's not just that it's our work called travelling fires.

[00:07:26] Guillermo Rein: Is that the standards and many papers by other people. And even in, in meetings, you people say that you can see the traveling fire. But traveling fires is a broad, concept that he just refers to a fire that travels. And some people were saying, what do you mean by travel?

[00:07:42] Guillermo Rein: What we mean by travel is that he doesn't stay put in one location. Uh, it may be large, or it might be a small, but it's moving across the compartment. And that concept, just that is moving. It is a departure from what structural engineers have been assuming for [00:08:00] the last 200 years. As you know, a structural engineers have a duty to design buildings that they don't collapse because of gravity, because of wind because of earthquakes, because of tsunamis, because of snow storms and also because of fire, right? So they, they have a duty to assume what is the fire that they're more concerned about for multiple reasons, they have to reach an agreement with the authorities and the clients sometimes about this. And when they decide what is the scenario they want to design against, then they make the structure be strong enough against that scenario.

[00:08:34] Guillermo Rein: And for many, many years and decades, actually, even centuries structural engineers have been assuming, , it's an hypothesis actually that the worst case scenario in a structure in a compartment is what we call flashover. And flashover is when absolutely every single piece of fuel that could burn is burning.

[00:08:55] Guillermo Rein: That's what he means. And it has different ways of being expressed. It has different [00:09:00] ways of being measure. It has many different ways of being study, but it really means that everything that could burn is burning. Not that everything has burned in the past or will burn in the future. No no, that everything is burning in that particular moment.

[00:09:14] Guillermo Rein: So every structural engineer said, well, that's pretty bad. Firefighters are very concerned about this. We have seen some structures failing when flashover had taken place. Therefore flashover is the worst that can happen. And this is an assumption that was not check for a very, very long time.

[00:09:32] Guillermo Rein: Right. And the origin of travelling fires is when, it actually started in, in 2001 after the horrible attacks of the World Trade Centre , millions of people saw that the fires that were started by the aircraft and the then were burning the office of the World trade center, everybody saw that the fire was not in one place.

[00:09:55] Guillermo Rein: Everybody saw that the fire was travelling And obviously that [00:10:00] led to the investigation ended too many things. So Jose Torrero, a professor in fire engineering at that time at Edinburgh, he was actually the professor in the group where I was he himself thought, oh, that's very interesting. He was involved in litigation regarding the World Trade Center and there was an ongoing discussion in with the lawyers and all the technical matter about what happens if a fire moves and or the fire deosnt move. And he thought, that's an interesting idea. We need to look into this.

[00:10:28] Guillermo Rein: And I thought that is absolutely brilliant Jose you're absolutely right. But we, but I could not be involved in the litigation. It was, that was in the side. So we said, okay, let's work on this as a research topic. So we came out with the first paper where we said, what happens to the heating, to the structure.

[00:10:42] Guillermo Rein: We were just, no, we're not doing a structural response. We were saying, how much does the heat the structure of made of a steel heats up? If the fire is moving, compared to a flashover. And the first thing that we saw is like, actually it gets hotter. If a fire is allowed to move than if you assume a flashovered fire.[00:11:00] And we started to travel the world literally with these findings to conferences, right?

[00:11:05] Guillermo Rein: And, and we had plenty of interactions. It was amazing. It was a paper that it not left anyone in the audience, in silence. People were horrified by things that. People were fascinated by things that we were saying, and people were in agreement or in disagreement, but he did not leave anyone, neutral.

[00:11:26] Guillermo Rein: And we realized that there was a need to continue looking into the topic. So we develop more research and we started to develop models that I will to, create, uh, scenarios that structural engineers can then use. And then we started to look not just that the thermal temperature response, not just how much the steel or the concrete heats up, but actually, what will be the structural response if this is in a building with multiple floors and the fire is travelling or it's on telly or vertically, and we continue doing this and now the [00:12:00] latest piece of work that actually a paper that was accepted today with Arup and a paper that was accepted, , two months ago, our experiments, experiments that we have. On the specific objective of scene, observing in detail, a fire that, that had travel

[00:12:16] Wojciech Wegrzynski: That's an interesting, interesting journey from, an idea, very clever, and one that really immediately changes your perception of what you see, right? it's this, type of , powerful concept. At some point I've, I've wondered what traveling fire is really about.

[00:12:32] Wojciech Wegrzynski: Is it, understanding the physics of a fire? Is it understanding the manifestation of the physics of the fire? Is it just a clever way for a structural engineer to really expose his structure to the worst thing? Or maybe a bit of all of the three above.

[00:12:52] Guillermo Rein: It is all of the three, obviously me specifically being an expert in heat transfer and a person that really likes fire I [00:13:00] enjoy understanding why a fire would travel if it does how it would travel. But that is not the only reason why we should study traveling, fires, uh, although I have a bias on this.

[00:13:12] Guillermo Rein: It is from my point of view, absolutely essential for the structural engineer, because it means that the worst case scenario for their structure is not just a standard fire or a flashovered fire that sometimes. And this is uncontroversial in the sense that it has been shown numerically and experimentally, that the worst case scenario for a structure could be, it's not guaranteed to be, but it could be a prevalent fire.

[00:13:37] Guillermo Rein: That means that our structural engineer cannot say, well, I just don't feel like looking into this just because I don't know. I just, I don't speak good English. So therefore I'm going to assume that it's a flashover cause I, well, okay. That's that someone may allow you to do this, but that's not good at.

[00:13:53] Guillermo Rein: If you are really looking forward to your structure being robust enough, you might want to look into the possible [00:14:00] worst case scenario. That could be a traveling fire. So there are many engineers around the world right now that are using traveling fires as a possible scenario to challenge their structure.

[00:14:10] Guillermo Rein: And when they have done it, they have some that sometimes the worst case scenario is travelling fire, sometimes it's not, sometimes it's actually quite interesting. Structurally speaking specifically the worst case scenario. Sometimes it's a still flashover fire type of behavior, right? The Eurocode or something like this.

[00:14:26] Guillermo Rein: But sometimes it's not. And we don't know enough in the sense that no one can say at the outset, in any compartment, what is going to be the worst case scenario? You, unfortunately, we have to go by hand and look at them and there is not just one traveling, fire, the bad news and people don't like it.

[00:14:41] Guillermo Rein: Is that there is, it doesn't exist when traveling fire. We, we recognize this was another contribution that we had with recognize our family of possible fires. We don't know if they're going to be fast or slow. We don't know if they're going to be big or large, but they are going to be traveling across the compartment.

[00:14:57] Guillermo Rein: And we made a link that the fastest fires will [00:15:00] be larger. This slower fires will be a smaller, that's actually lactated by physics. and then we just, ask this to the engineers, to look into the family of fires, not just one fire.

[00:15:10] Wojciech Wegrzynski: And it's not necessarily a well, it's never the same fire that will be the worst for all structures. And one structured will be one thing. Others will be other right.

[00:15:18] Guillermo Rein: in indeed, in that definitely it's a structure. Its compartment has its own worst case scenario, but what we found and we don't know why, why it, and this is actually a mathematical problem, more than a physical problem. What we see is that the worst case scenario tends to be in relatively a small. Which are relatively fast. They actually in person touch of the floor area. What we see is that between 10 to 15% of the floor area, when the travelling fire is that size. And it's traveling across the compartment that leads to the largest heating of the structure being steel, concrete, or timber. That's what we've seen.

[00:15:55] Guillermo Rein: Mathematically so when at some point we'll look into why that is happening, but it's a [00:16:00] balance between, the highest temperatures which are produced by the flame being, uh, long enough. And that then the smoke, which is, preheating and post heating is there for, long enough as well. And the combination between the flames and the smoke leads to a largerst temperature.

[00:16:18] Wojciech Wegrzynski: So with this percentage is in the way, how you define this traveling fires. If I understand it correctly, you can imagine a large room. Where is the virgin fuel that you will eventually burn be it, uh, desks, wardrobes, whatever is in an open space, and then the fire starts and, it eventually spreads forwards, , igniting more and more fuel, but there is not an infinite amount of fuel behind it.

[00:16:44] Wojciech Wegrzynski: So it burns out as it moves. So it becomes time related phenomenon. Can the fire live long enough in one space to ignite another space before it burns out And now the velocity in how the fire will ignite the, [00:17:00] the further things is related to, to heat transfer more or less and ventilation conditions and, very, very complex, physics actually to, to calculate how it spreads.

[00:17:09] Guillermo Rein: we, yeah, actually we can't calculate how it

[00:17:12] Wojciech Wegrzynski: that's what it wants.

[00:17:13] Guillermo Rein: can only assume how they could spread and then look into the consequences.

[00:17:17] Wojciech Wegrzynski: That, that's what I wanted to say. It's I mean, if the world was built only from PMMA slabs, maybe we would have a chance, but PMMA is usually found in the fire laboratory is not really that much in, in open space offices. And, it's not an easy way to solve it. So you had to find a proxy for the spreads. How did you solve that issue with this methodology?

[00:17:41] Guillermo Rein: so there is a brilliant question and line of argumentation because there's something that I want to tell you, or first something to highlight. We haven't mentioned yet. We know that traveling fires appear or traveling, or the fire wants to travel when the compartment is large, either compartment is, is small and they always ask me how is small and [00:18:00] I have, we don't know, but we think that it's going to be a smaller than a hundred meter square.

[00:18:05] Guillermo Rein: So for example, my office is definitely the fire is not going to travel. So if someone is interested in the structural response of the environment in my office, just let them know that it is not going to be a traveling fire and the flashover fire is going to be okay. And it's going to be the worst case scenario.

[00:18:20] Guillermo Rein: But when you start to move in open plan offices and large spaces where there is fuel. The structural engineers because of inherited and the legacy training that they receive, they immediately said worst case scenario is a flashover. But if you ask other fire people, for example, a forest fire expert, they will tell you, we rarely see anything similar to the concept of a flashover.

[00:18:43] Guillermo Rein: Only the only in a valley they would say something like this. What we see that will tell you a forest person. We always see the fire spreading. And there is a leading edge where the flame is igniting the next fuel element and is moving forward. And behind that is [00:19:00] what we call the trailing edge, which says when all the fuel that has been burning for about 20 minutes already, actually there is no more fuel on the flame stop.

[00:19:09] Guillermo Rein: And between the leading edge and the trailing edge, you have a fire of some size that is travelling and the size of the fire could actually vary. Sometimes it could be large. Sometimes it could be a small because it depends on the interplay of the velocity of the leading edge and the velocity of a trailing edge.

[00:19:25] Guillermo Rein: So the two edges are unrelated to each other, but they are related to the fuel that is burning by flammability properties and by fuel load. So the two of them, that's why you can end up with a large fire, or you can end up with a more fire related to a slow fire or to a fast fire.

[00:19:41] Wojciech Wegrzynski: And how did you, proxy it, , like what did you do to solve the unsolvable problem of physics of the fire spread? Because to model it, you need a number,

[00:19:52] Guillermo Rein: so, yeah, no, it's a very good question. And this is when the different schools of thought will have different answer to that question, right? So [00:20:00] a physicist or a computational scientist will tell you, you obviously take the 3d development Navier-Stokes equations, Arhenius equations, and you couple, all through Fourrier's Law and Stefan Boltzman's Law, and you push enter and you spend three months and you will have.

[00:20:15] Guillermo Rein: Especially a distributed model of how the fire spreads with, obviously that's possible as an engineer. , I could do that, but what I prefer to do is to produce something that can be used by the people who design buildings, the structural engineers, right? So I want my research. These aren't aspiration. It doesn't happen often, but I want my research, our research to be used in the real environment.

[00:20:39] Guillermo Rein: So actually I can, I can sleep better at night thinking that I did my tiny little son, beat into having a safer world somewhere. and that means that if I come, come out with a 3d, fully transient fully physics model of the whole enclosure is not going to be used by engineers. So what I did is we spent significant amount of time into studying how engineers [00:21:00] were using design scenarios.

[00:21:02] Guillermo Rein: And we saw that they were going to straight into flashover and they were using either the standard fire which is cheating because the standard fire doesn't ever end, right. It could be an infinite fire, infinite fires and exist in nature or the one that is very popular that we use a lot for our comparisons is the Euro code, the Eurocode use mostly in, the UK actually.

[00:21:25] Guillermo Rein: which is really funny, but it's very popular in the UK it has the, parametric fires, which are fires that are not infinite, which makes me very happy because I believe in conservation of energy and contribution of mass and these fires could be hot and short or could be cold and long or in between, it creates the concept of a family of fires.

[00:21:44] Guillermo Rein: It is not embraced, but most engineers, but they were actually the first ones to say, we just don't know which one did we just know that it's going to be a range of them. And we, and we look into that, right. And we realize, so they take that, they take an one temperature in the whole compartment.

[00:21:59] Guillermo Rein: The [00:22:00] compartment has thousands of temperature points, but they say, just take one, the average or the most representative one. And that is heating the structure. And they actually, they do, they keep transferring a relatively nice way. They assume a heat transfer coefficient, which is not, a value that is relatively acceptable or we should do better.

[00:22:16] Guillermo Rein: It assumes irrigation and it just solve for the heat transferring to the steel or the seal or the concrete or the, of the timber. And we thought, okay, so let's take that restructure and alter as little as possible, but allowing traveling fires to come in. So if we come out with 27, temperatures changing in time and space, the structural engineer cannot use them and we will have to wait 20 years to, for them to be ready.

[00:22:40] Guillermo Rein: So we said, it's removed that one single temperature by. One temperature that at the beginning is not too hot. Is this arriving in smoke to the location? Then at some point it got really hot, which is the arrival of the flames. And then it goes down again to the smoke because now the fire has [00:23:00] burned.

[00:23:00] Guillermo Rein: Whatever the fuel is under thisstructural element has moved away. And then now just focusing for how long is the smoke preheating for how long is the flames, heating and for how long is the posterior heating after the flames?

[00:23:13] Wojciech Wegrzynski: And this is for different locations in your building. So would calculate this for like I dunno, the slab next to the fire, the slab 10 meters away. It slab 20 meters away and each of them would have their own

[00:23:23] Guillermo Rein: so then in reality, that is a possibility, different points of the compartment, we'll see the arrival of the smoke and the flames at different times. So it would end up in different final heating. What we saw very quickly is that. It is true that the final maximum, not the final temperature, the maximum temperature, which is one thing that the structural engineers like to look at, obviously as a mechanical engineer explaining heat transfer.

[00:23:46] Guillermo Rein: I love the concept of maximum temperature because it's something that I can calculate. And I love things that I can calculate uh, but in reality, a structural engineer needs to focus on the structural response, not on the thermal response. And when the structural [00:24:00] engineers start to do complex calculations from the structure that is away from my expertise.

[00:24:06] Guillermo Rein: So they have my full admiration and they will always have my collaboration to work on this, but I encourage them not to stop at the temperature, which is what I should work. They should go into a structural apart. But anyway, so talking about something that I can say more about is this the temperature, the maximum temperature in different parts of the compartment.

[00:24:24] Guillermo Rein: It is relatively similar in all places, but it tends to be higher at the end of the compartment. But because we don't know where the arsonist or the accident is going to happen. We don't know what is the concept of the end of the compartment, because we just don't know where it's going to start. So therefore you run a, some traveling fire, and you always look into the maximum temperature towards the end, and you use that temperature of a steel or the concrete or the timber as the requirement, or the challenge to your structure.

[00:24:53] Wojciech Wegrzynski: So coming back a little earlier. You've said that, when you were developing the methodology, [00:25:00] the concept of flashover was very strong. And we, we see today that, we perceived the fires as flashover fires or pre flashover fires. Usually the flashover is the point where the fire dynamics change.

[00:25:12] Wojciech Wegrzynski: And this has some, you know, historical background going back to like that, i dont know, fifties where the first single zone models were developed, or even earlier where, people who are just assuming that the flashover fire is the fire. Everything else was a small fire. So now we entered these moment wherein we figure out, okay, may be this, flashover scenario is not the most onerous one, or maybe even entering a discussion.

[00:25:42] Wojciech Wegrzynski: If a flashover in the given compartment can even a cure, because if you use, uh, MQH correlation, McCaffrey Quintiere Harkeload that allows you to calculate, what heat release rate essentially you need in that compartment to create a flashover. You sometimes don't have a solution for that in the given compartment.

[00:25:58] Wojciech Wegrzynski: So. Now on the [00:26:00] other hand, you have the whole world of fire resistance, the whole world that is you know, very juxtaposed to the post flashover fire. It is the post flashover fire world. And suddenly we are talking about the physics of real fires in the building. And it's interesting, but when you compare that with very unrealistic way, how we create the proxy of safety through fire resistance concepts, for example, do you think that this needs to be changed?

[00:26:29] Wojciech Wegrzynski: Like the whole world of fire resistance should change to adapt for use in traveling fires or maybe the traveling fires had can penetrate the weld fire resistance in a way, is there a link, can we find one?

[00:26:40] Guillermo Rein: So it is happening and it's definitely happening slowly, but it is happening with our lifetime. I'm happy to say that traveling fire now is in, in the Eurocode, it's in the ISO and it's in the British standard. And it's just a matter of time for it to also be in the Society for Protection Engineers and other codes.

[00:26:58] Guillermo Rein: So it is happening. The now is part of his [00:27:00] standards. It's not just that there are many papers on it. Uh, computational, theoretical and experimental is, is that it's already in the world of design. And I know because I'm like, well, I used to know, I used to be updated with the number of buildings around the world that have used traveling fires.

[00:27:15] Guillermo Rein: Not that they, they were designed against the traveling fire, but that the engineering team had considered if a travelling fire was the worst and it was sometimes, sometimes it was not. And they were all beautiful. Buildings, literally were iconic. They were not like cheap buildings that you do at someone that's in a, in a minute is a building that people put love and attention and ture engineering and, , and this type of teams, the ones that are aspired to the true engineering calculations are the teams that are more susceptible to embrace traveling, fire. So it is happening. just one thing you, you referred to the concept of fire resistance. I really disliked to use the concept of fire resistance as a very, very specific small more definition related to standards and to practice. For me, fire resistance , is a combination of [00:28:00] two words that means, the resistance against fire.

[00:28:03] Guillermo Rein: And I think that is a lot of work to do into how many engineers currently design for the resistance I against fire. But I refuse to assume that those two beautiful words together, , only mean that they, they mean also the future of fire resistance.

[00:28:19] Wojciech Wegrzynski: Yeah. I've asked that because it's, this, this concepts are as far from each other, as, as the real fires are from the fire resistance in a way, which is in a way, a horrible, uh, conclusion to make. But th but that is that is the truth. Now, We know how the idea was born and we know what's triggered it. What were the goals? And now, now it's flight to Poland. And tell me, what made you burn a cow house in the middle of Poland to, to prove a point?

[00:28:46] Guillermo Rein: It was a beautiful, absolutely beautiful, work that actually you, you had a significant input into, and it was very important to have met you, but I'll start with when we were presenting the work, not just at the [00:29:00] beginning, as we were progressing and presenting papers. Uh, as I told you before, it was very rarely that an audience will stay quiet after hearing about traveling fire especially if I was presenting by the way.

[00:29:10] Guillermo Rein: No, I have, I have the gift or not of making audience, rant, uh, one of the questions that I was getting actually, I think is the number one question that there are, by the way, obviously I didn't do this work by myself, quite the opposite. But there are key players in this work. It's not just Jose Torrero or Jamie Stern-Godfried.

[00:29:28] Guillermo Rein: That was the first PhD student doing this, or Egle Rackauskaite who did the PhD with me and Imperial or at Heidari Mohammed Heidari who did an, also another PhD thesis on this and more students that are coming. Altogether when we were presenting the number one question that we were getting was, why do you say a small compartment?

[00:29:48] Guillermo Rein: What, what is a large compartment to know when they have to worry about traveling fires? Right. And we didn't have a question for that, and we still. And then, then number one, complaint complaint, not question was fires don't travel. [00:30:00] We literally hear that very often by some very reputable scientists and engineers.

[00:30:06] Guillermo Rein: Uh, obviously not in front of hundreds of people, but to us. And in Britain, they said, this is bollocks, Guillermo fires don't travel. And it was very interesting because if you talk to the fire brigades, they will tell you they hardly go a month in the lifetimes when they're not see a fire travelling. And I thought to myself, what kind of a state of affairs is this?

[00:30:26] Guillermo Rein: Where some of the luminaries of our field claim that fires don't travel and some of the people at the forefront of fire protection, which is when everything fails and the fire has to be fight, are saying that, of course they travel. Uh, I just don't have time to take measurements for you Guillermo, because I'm trying to save life and mine included.

[00:30:42] Guillermo Rein: So we, we obviously thought that is more work that needs to be done here. And one of the things. Can you show experimentally that fires travel so the first thing that we did with Jamie is we look into the literature. We actually revisit the literature with a question that no one has ever posed before [00:31:00] is in this experiment, the fight travel. And we found evidence, I think in the figure of five experiments, where there was evidence that the fire had travelled. There was also lack of comments in the paper about this behavior. People were not looking at it. People were not interested in added people were oblivious to the fact that thermocouples will racing up and down.

[00:31:22] Guillermo Rein: Almost like in symphony at different times, they were like, we don't know what this happened there's a comment that actually one of that says, and we don't like this, we try to get rid of it, but it just doesn't go away. Uh, the fire keeps being in the wrong place, right? It was, it was fascinating.

[00:31:36] Guillermo Rein: So actually traveling fires have been observed, but people were blind to it. They were not interested and they were not actually able to. Then we obviously recognize the need to do experiments. There was a very large proposal led by Jose Torrero that was written here for the UK research agency. And when the funding was one to the experiments I happen to actually at the same time, go to Imperial and [00:32:00] Jose Torrero to Queensland.

[00:32:01] Guillermo Rein: And that meant that the team got dissolved and it meant that the experiments actually happened. But unfortunately I was not part of them. It happened in the absence of any influence, positive or negative that I could have these experiments, which is a beautiful set of experiments. 3 sets, one in theory, with Gus burners being operated at different times, that was forcing the fire to travel to, to speak.

[00:32:23] Guillermo Rein: BRE also had with wood cribs, where the fire travel at the speed that he wanted to speed. And then an experiment, a beautiful experiment in Lisbon, in another compartment. These are the first time that the experiments, they were design and they were analyzed with the objective of seeing a traveling fire and they saw a traveling fire, and it was actually the first post traveling fire era experiments that were able to see this.

[00:32:49] Guillermo Rein: There was another experiment in the Czech Republic. With David Lange. We were involved in this actually Egle was there. Heidari were there , two of my PhD students working on the topic, the were there in the Czech [00:33:00] Republic, the fire did travel in a completely different manner as expected, but it travelled

[00:33:04] Guillermo Rein: and we just gathered all these experiences and said, well, we want to also, do more experiments. So I presented traveling fires in Warsaw, in a conference where you're, where Wojciech and Piotr uh, was also present. And at the end of when I came down from the podium, you guys approached me, and said, what do you need to do this experiment?

[00:33:23] Guillermo Rein: And they literally were saying, you're crazy. This, this, this cannot be done. This will be impossible. You need a very large facility. You need a lot to building. And it was Piotr who says, well, I know a lot of fire brigades. I get back to you. And during the course of six months, he was calling me every month saying I found this building.

[00:33:42] Guillermo Rein: He was sending me photos. And we were, I was saying, no, no, that's, that's not, thank you. But not. And one day he sent me a building. I thought, oh wow. That building will be great. It's open space, plenty of windows. And then he went in and said, oh, it cannot be done because it was built on top of, uh, transform a station.

[00:33:58] Guillermo Rein: Transformer a station with [00:34:00] oils and say, yeah, no, I will definitely not go well. And then months later he came and said, okay, I got it, but sorry, can you tell what used to be a cow house or with the house? I was like, what? And then he told me the photos. It was perfect. It was incredible. It was literally open plan. wide range with multiple amount of windows is important to have a lot of windows. So you'll have plenty of, ventilation that imitates a, see if the compartment will be even larger. Because one thing that is important in traveling fires is that the fire that is not influenced by the presence of a wall, now ceiling and floor is fine, but it's the wall.

[00:34:34] Guillermo Rein: If the fire is seen always the influence of the wall, because the wall is changing, the flows is arriving with fresh air. If there's a window, , that if it's a wall that doesn't happen. And that is actually a recirculation and the wall itself could be, absorbing a lot of heat or it could be actually insulating the fire.

[00:34:50] Guillermo Rein: And that's what we wanted to do. We wanted a large compartment where the effect of the wall is minimized as opposed to a small compartment where the effect of the wall is maximized. Literally in a small [00:35:00] compartment, in a furnace, what you do do a lot of furnace tested. There is not one molecule of that place that cannot stop feeling the wall very close by,

[00:35:09] Wojciech Wegrzynski: The furnace is basically a structure of walls that radiate on your sample. That's the principle

[00:35:15] Guillermo Rein: and, and the flows are all controlled as well by the presence of the wall so all these molecules that are inside there are chemicals, reacting, and fully aware. That's somewhere nearby. There is a wall. And what we want to move is we want to move into a place where the fire. Yes, of course. He knows that our walls, of course the fire knows that is enclosed, but not that in, not that intimately related to the walls.

[00:35:38] Guillermo Rein: So that's what we wanted. Not only just a large compartment, but plenty of openings. That's that note, it will actually emit. I say to imitate that if heavy were to be even larger,

[00:35:47] Wojciech Wegrzynski: Okay. Like if it was an infinite space. Yeah.

[00:35:50] Guillermo Rein: That will be obviously ideal and infinite a space where there is no walls that is yes, ceiling and floor and let the fire do whatever he wants to do.

[00:35:58] Guillermo Rein: As you start to bring walls, you are [00:36:00] complicating the problem. And obviously at some point you ended up in a small compartment. And the idea was, if this happens flashover, it will not be possible. Or it will be unlikely with the typical fuel loads of an office building. Right? And then we found this place.

[00:36:15] Guillermo Rein: You guys talked to the fire brigades, and the fire brigades of the local town, where this was happening, were happy to involve. It was amazing. They wouldn't involve, uh, we found the sponsors to this crazy idea, ARUP and CERIB in particular and EPSRC, we need to under Society for Protection Engineers. We always need to thank a sponsor, to support crazy ideas.

[00:36:34] Guillermo Rein: And then there was just an army of PhD students and visitors, and we send them all to Warsaw, there for, three weeks. And they designed because actually it has to be designed. They design a fuel loads. We bought sticks of wood 3000 of them, we put them meticulously. We ignited we had many different cameras and thermocouples and different devices measuring what he [00:37:00] was going to happen.

[00:37:01] Guillermo Rein: And what we observe is that the fire travel.,

[00:37:03] Guillermo Rein: we also discovered many things that we were not ready to do. For example, we lost a lot of our cameras. Uh, it was a lot of fun. We didn't know it was going to be a lot of fun. It was safe. We were not sure about that, but we also discover that the fire accelerated,

[00:37:17] Guillermo Rein: obviously you said these things in hindsight, and then in the end, people say, of course it accelerated it's like, of course it accelerated, just show me the paper where he says that he was going to do that.

[00:37:26] Guillermo Rein: So the fire accelerated in the sense that he started very small and very slowly and end up being a relatively fast fire, towards the really end of it to the point that it, then the question is about what happens if it's even larger, right? Because if he's accelerating.

[00:37:41] Wojciech Wegrzynski: In hindsight, when we've discussed the ideas for your experiment, I've run some CFD to see what would be, the heat feedback in front of the fire uh, with different sizes of the fire that you could get. And what I've observed with this, CFDs was that this with every like a hundred kilowatts of 250 kilos, that I've [00:38:00] added to my fuel, the radiation in front of the fire did not, increase linearly, but like exponentially.

[00:38:06] Wojciech Wegrzynski: And then well, it's the fourth power of temperature and temperature is like correlated with heat release rate. So it's kind of obvious, but. I mean, it was obvious this, as the fire will go larger, it will have a bigger impact on the fuel nearby, which means it will change the way, how it ignites. That's an easy thing to think of.

[00:38:28] Wojciech Wegrzynski: The hard one is how much and when then these two things, it was not possible. And then we come back to the issue of, the physical modeling of the fire spread in large compartment, because this balance in, in heat transferring all of the modes of heat transfer is, is almost unsolvable for such a complex fuel is such a complex, , setting of, of a building, you know, and that makes it beautiful in a way.

[00:38:50] Wojciech Wegrzynski: And. Also, I think that's my own opinion The flashover is the manifestation of the same thing. It just happens in within the second, [00:39:00] but it's essentially the same feedback loop that's going on in your, in your compartment, the more heat you release, the more radiation, easier to ignite. Eventually you go to self ignition temperature and, there it is in the whole room is in fire.

[00:39:13] Wojciech Wegrzynski: So , this is the difficult one to capture. And you had, this very clever idea on how to measure it with, with cameras. It's a big loss that they were melted in this experiment. Luckily you, uh, you are brave enough to pursue these again. And we've met once again in, in the same cow house, two years later to repeat the experiment.

[00:39:35] Wojciech Wegrzynski: And it also was, , a lot of fun, but let's, let's go back to, 2017 when the first experiment happened. so when you saw that. What were your feelings were, were you like yes. We've proven it happens or were you like, why the hell did it accelerate?

[00:39:51] Guillermo Rein: No, no. At first, I mean, it was a very realistic fire in the sense that it was a true building with true, incredible amount of smoke. [00:40:00] Probably the, the Warsaw airport can see us and everything. So in the moment, if it was very confusing, uh, we were very happy that he had finished, but we didn't know very well what had happened. Everybody remembers at the beginning he was traveling and everybody remembers the panic because the firefighters were silencing and all the external flaming. And also, I was particularly very worried because we lost, many, many cameras. We had protected the cameras. They were thermally protected, but we glue them into the wall of the compartment that was made of a layer of mortar. And the mortar literally just exploded when the fire was coming and it was taking our cameras to the floor. So I was very worried after the fire, we didn't have data, but Egle Rackauskaite did absolute wonderful things and was able to use handheld cameras that survived the fire. And with artificial intelligence and computer vision, she actually was able to track the two fronts, the two edges of a fire, she was able to track the movement of the leading edge. That's already an accomplishment of a paper we saw and we [00:41:00] observed because we wanted to observe that what was happening to the leading edge of.

[00:41:05] Guillermo Rein: And we also observe in detail and Egle was mainly behind this, the trailing edge of a fire. And we were able to plot the two of them in time and in when, in between them, where you have is the size of a fire. So we say, we saw that at the beginning, it was this small and it was the leading edge was going faster and accelerating faster than the trailing edge that was making a bigger fire.

[00:41:27] Guillermo Rein: And then at some point the remaining part of the compartment was all engulfed. But it was interesting because we did not observe a flashover. if you go to the state of the art of what scientists call is flashover, not what someone that is in the moment of a, experiment says, oh, that feels big.

[00:41:43] Guillermo Rein: Oh, it must be a flashover. Well, that's not a scientific definition. If you use the scientific definition of flashover Obora is called X one, this experiment was not a flashover experiment. It was not sudden. The average temperature and the compartment was definitely not 500 Celsius.

[00:41:59] Guillermo Rein: The ceiling, [00:42:00] uh, the heat flux to the floor of the ceiling, was actually not above the level that typically we site and not all the windows were having an external flaming so it was not a flashover. Yes, towards the end, it was a big fire. And that for us was the accomplishment. It was to show scientifically to the community that, that travelling fires exist.

[00:42:19] Guillermo Rein: That travelling fires is different thing that flashover and that there is a lot of things to learn. For example, the fact that the leading edge was moving faster, that the trailing edge and that the difference in the two of them was actually growing,

[00:42:32] Wojciech Wegrzynski: From my perspective. I was there with, Francesco Restuccia another PhD student of yours. We were given a perimeter of the roof to protect with a hose because the building was, it was a concrete building, but the structure of the attic was a wooden. So we had to wet the, joint between the wall and attic, outside of the building to, to not have a collapse of the roof on the, on top of the building. [00:43:00] And we were there with Francesco wetting this thing. And then we clearly see, you know, these flames moving away from us and we together with the relief, ah thank God that fires travel as it's moving away from us and it will soon be safe.

[00:43:15] Wojciech Wegrzynski: And it was just, it just a few minutes later. So yeah, that, that was our observation on the nature of traveling fires. And you've also mentioned that Egle has done a fantastic job, uh, reconstructing the, event from the external observations like we did with our cell phone cameras, there were some cameras placed outside the building to just, create these bunch of images of what was happening around.

[00:43:38] Wojciech Wegrzynski: They were not the primary scientific devices used in

[00:43:41] Wojciech Wegrzynski: this experiment.

[00:43:42] Guillermo Rein: the primary ones. All of them

[00:43:44] Wojciech Wegrzynski: Yeah, but, but what you've said, in the beginning of the interview that it was first observed in World Trade Center where people literally seen it. It's travel is the same with happened in 2017. It's just, we've done it uh, scientifically or Egle has turned our [00:44:00] unscientific observations into a scientific study. So, so that's phenomenal.

[00:44:04] Guillermo Rein: Well, I mean, obviously the World Trade Center was a massive, tragedy. But also it didn't have a name. So for example, if you read the investigation of the World Trade Center, the many of them, they don't mention this, uh, word they don't say travelling fires the modelers from NIST Kevin McGrattan and his team did something very interesting. They actually simulated a traveling fire in FDS. In fire dynamics simulator. They just didn't realize that what they were doing was a breakthrough compared to what the structural engineers were doing. So I was trying tell Kevin McGrattan that and he was very casual about it.

[00:44:35] Guillermo Rein: He's like, I felt the need to burn them the office, areas just one by one and let the fire be in different places I thought. But Kevin, that's a traveling fire says, well, I don't know what it's called, but it's just what we did. I thought that's amazing. So we actually cited , the work of Kevin McGrattan and the investigation as evidence that fires travel. They didn't call it like that, but that's actually what the.

[00:44:56] Wojciech Wegrzynski: Now let's go into the model itself. I've [00:45:00] seen the evolution of the model I'm inside of that. So, so first, earliest version, developped the, in the PhD of Jamie Stern Godfried, . It, it had this. I assumed temperature at that, that the maximum peak temperature that the structure will be exposed to.

[00:45:16] Wojciech Wegrzynski: I, if I'm not wrong, it was twelve hundred degrees Celsius Then um, I remember PhD of, Egle Rackauskaite, where she has, considered that it's, not an uniform temperature and it will, there are factors that influence this temperature and there were some corrections input to that. Then, Heidari, did the flame extensions.

[00:45:38] Wojciech Wegrzynski: And another iteration of, changing that. And we know there are efforts ongoing in the world to, , use even more complicated methods to use it. Ideas to zone models to use, um, some hybrid zone models with smaller cells up to CFD scale where you just use full CFD to determine this, and my question is. I see [00:46:00] that, in a way the power of this method comes from the fact that you can account for hundreds, if not thousands of fire scenarios in compartment, you've said you don't know what the fire will be.

[00:46:10] Wojciech Wegrzynski: You don't know where the file will start. So what is the furthest point from your fire if you don't know where it started, and, there is this difficult balance of this triangle of, you know, accuracy, computational efficiency, and when you have a true solution, let's say the closest to the truth. So, so what is your take on that?

[00:46:29] Wojciech Wegrzynski: How detailed must the model be to be useful and, is, approximate model still useful, for example, in in structural engineering,

[00:46:38] Guillermo Rein: Yeah, it'd be great question. Wojciech, the question that every single engineer ask themself at any discipline. Not only does in fire engineering is how complex does my model have to be? You know, that to be useful. As engineers, we recognize that the complexity has to be justified. So we don't just embrace complexity just because we think is fun or fascinating or, [00:47:00] uh, or one has told us we embrace complexity because we have a professional or scientific argumentation of why it needs to be this complexity and no more and no less.

[00:47:10] Guillermo Rein: So I would, the particular approach to traveling fire actually is a good example of this. The methodology is that existed before traveling fires were very good and they were parading our level of safety as to close safety. But we thought that with a minimum amount of more complexity, we could enable the structural engineers to embrace a set of scenarios that they was not in their radar at all

[00:47:33] Guillermo Rein: And And we design traveling fires methodology. The first, the second, I mean the six of them, the eight of them that we have developed. The eight of them are minimal increases in complexity compared to the previous use of any model by structural engineers, such that they could embrace it. And that without too many difficulties, they could bring it into the design, daily lives.

[00:47:56] Guillermo Rein: This is in comparison to compete disruptive ways [00:48:00] of doing things. For example, people who were bringing CFD, not in a way a NIST was bringing a CFD design the scenario with a traveling fire. They were saying, embrace my CFD. Structural engineers are not going to be embracing CFD in the near future.

[00:48:14] Guillermo Rein: It takes way too long to compute. Yes. And actually, you know, someone says, and it gives you a accuracy actually. You know what? It doesn't even give you accuracy. Because he's actually not true that CFD predictions are the current state of our knowledge of fire gives you more accuracy, but for sure is give you more complexity and longer times and more difficulties.

[00:48:32] Guillermo Rein: People who have said structural engineers need to use CFD. That's not going to work not in the next 50 years, at least because they are busy enough with their finite elements. They're busy enough with the structure. So the role of a fire engineers or the fire scientists is to help them increase the level of sophistication of that analysis without making their lives impossible.

[00:48:51] Guillermo Rein: That's what I wanted to do. This is what I can claim that travelling fires doing. And that's why CFD approaches are not going to work in this problem in the near field because the [00:49:00] next and getting this has, that is doing this cannot catch up on the tool. Right. Um, but I want to make a comment on what you said. There are, uh, as far as I know, there are 15 models. I don't call our work models, but actually it's true that our models, because that conceptualizations of a phenomenon, we've got the methodologies to make sure that people don't forget that the model is attached to the way it is going to be used. The model per se is not in, in the air, in the abstract is married literally to the way it can be used.

[00:49:29] Guillermo Rein: And that's why some of the simplifications are called upon because they have to be compatible to the way that it's going to be used in design. If I were to be doing traveling fires, not for design, not for a structural engineers, I will be doing a complete different approach, more similar to how I do forest fires, but I want it to be used in a methodology.

[00:49:47] Guillermo Rein: So there are 15, methodologies, existing, six of them are ours. Two of them existed before we arrived. So when we revisit the literature state it with Jamie, not only we discovered experiments with people have seen travelling [00:50:00] fires, but obedience to it, we discovered that traveling far had been independently created twice before. And the authors didn't know each other. One of them was in Belgium and one was in New Zealand. They, the two of the authors, they didn't know, obviously they didn't use the word traveling fires. The two of them were statistically different, but the two of them were allowing the fire to move in different ways with different assumptions.

[00:50:24] Guillermo Rein: Obviously we claim that our methodology at that time was, more, complete and more consistent with heat transfer and all these things, but that's up to debate. And since then there have been the model by Danny Hopkin. Now in OFR, the model by the university of Edinburgh, they have another model of their own.

[00:50:41] Guillermo Rein: That is a model in the Czech Republic. Uh, there is another model coming from Belgium. They just keep popping up. And that is really good news. That means the concept is catching. Most of them at this point, use the word, traveling fire, which is really good because that in a way it's a way to integrate the literature. Although actually, I have to tell you that now there are papers that are coming out with any. [00:51:00] That's a pity. Now they're creating new names that are saying, no, its not a travelling fire it's a are spreading fire. No, it's not spreading fire. It's I'm moving fire anyway, but that's the tribal behavior of scientists.

[00:51:09] Guillermo Rein: And it's good that there are different ways of modeling this because with time we will be combining and choosing the one model or the parts of the models are combined together. Allow engineers, structural engineers to do their job better.

[00:51:23] Wojciech Wegrzynski: like what you're saying about the, the complexity that has to be justified. I see a parallel to my world of smoke control, where you have a smoke plume entrainment correlations that allow you to calculate the amount of smoke that travels upwards in a smoke plume above a fire.

[00:51:43] Wojciech Wegrzynski: And, uh, you have CFD, which essentially you do the same thing and there are. Buildings or compartments in which empirical models are more than fine to be used and they give you good representation of what the outcome of a fire in such a room would be. And there are rooms in which she, you [00:52:00] have to use CFD because the abstract, uh, space, It's not compatible with the complex flow.

[00:52:07] Wojciech Wegrzynski: That will be there. Sorry that the, so this is a simple model is not compatible with the complexities of the space in which it will be placed because it was developed for the empty space in a similar way. Maybe the simplest, , traveling fire models are compatible with, with simple open plan spaces.

[00:52:23] Wojciech Wegrzynski: But as soon as you start to turn your building into a labyrinth, they may lose the ability to, uh, to predict this, the scenarios or give this. But, uh, that that's, I, I guess that is the future. And, at some point we will more, more or less, gets to a point where we have a tool for every fire scenario, maybe artificial intelligence or something fancy will emerge at some point that will help us figure out , which traveling fires are the one to, to seek, or maybe a world in which you use the simple model to screen for potential scenarios.

[00:52:57] Wojciech Wegrzynski: And then you solve the most onerous [00:53:00] one. That's also, I, can see that that could happen, but the great thing is, I think the biggest disruption this method has created is to decouple the structural fire engineering from this, fire resistance paradigm and this blind vision of the fire will be there. It will take the whole room let's solve for that. We're done. to, to just decouple structural fire engineers from this concept is as powerful for me as understanding the complex, fire behavior in the building. And the method has already achieved that no matter what the fidelity of it, this,

[00:53:33] Guillermo Rein: What you've mentioned is actually quite important to disassociate structural engineering from only flashover. There is another scenario that actually was there before traveling fire, which is localized fires, which is recognizing that sometimes there is no fuel everywhere.

[00:53:49] Guillermo Rein: There is just a concentrated amount of fuel and that if your burns, it could be a, a local threat to a structure that crosses that path or is nearby. Or I call them the fascinating part that I can say now is [00:54:00] that they did that, but they did not realize the difference between the space between the localized fire and the flashover.

[00:54:09] Guillermo Rein: They didn't realize that in reality, a localized fire that is allowed to move it is, um, it is the link between the two of them. But now we can say, we have this continuum, there is a localized fire that doesn't move. There is a traveling fire, and then there is still a flushing.

[00:54:24] Wojciech Wegrzynski: That's beautiful. And, tell me where you're going with it.

[00:54:26] Guillermo Rein: Well now. Okay. So have Heidari, he has just graduated with his PhD and Mohammed Heidari from CERIB and what he did is he him, he fixed our near field. Uh, we're near our field. As heat transfer experts was not up to standards of heat transfer. We got a lot of flack from that. what he did is he improved it in a way that doesn't make it more complex.

[00:54:48] Guillermo Rein: So he actually hit the sweet spot between being simple and being more, more accurate and more comprehensive. So we are actually very happy with the work of Heidari. [00:55:00] Uh, the next step we're thinking of two of them, one is to make it probabilistic and Heidari has already done that. The fact that it's not just deterministic, but over a range of families now he's actually that you could have different fields,

[00:55:15] Wojciech Wegrzynski: a range of ranges.

[00:55:16] Guillermo Rein: And you've got to have a range of ranges.

[00:55:17] Guillermo Rein: You could have a range of flammability parameters and you can have a range of fuel loads. And then you'd run this through the catalog approach and you end up having probabilistic behaviors, which it was fascinating, but we just scratched the surface with Heidari on this. But there is, it is probabilistic traveling first and there is another one, based on the work that we're working with ARUP

[00:55:36] Guillermo Rein: so it's a published paper policy in Fire and Materials. It's literally just this morning, where, uh, it was, it's fascinating where a Obora from Warsaw was replicated brick by brick. Okay. So these a, these all, 50 years old cow house forgotten in Warsaw has now a twin and he's not a digital twin is an actual brick twin in [00:56:00] France in CERIB

[00:56:00] Guillermo Rein: And he was still standing by the way. And he's literally the same, same doors, same walls. same dimmensions, everything.It's just, these are brand new and so far, , very in very neat conditions. And instead of burning a concrete structure, which is the regional off Obora, they were burning a timber structure. They were timber columns. They were putting up timber ceilings, CLT, and glulam in particular. And they put the fuel loads that we did in Obora and they started to observe what happens. And the first thing that happens is that the fact that you have added more fuel and you put that in the ceiling, which is the most allowable, there's the part where it's exposed to the highest heat fluxes

[00:56:38] Guillermo Rein: yes, indeed. He changes the behavior of a fire. And actually what we saw is that what we saw that day was actually closer to what we will call flashover. It is a fire in a very large compartment that even, I would say it almost meets the scientific definition of a flashover. It doesn't really do, but it almost defined a flashover.

[00:56:59] Guillermo Rein: So he was a [00:57:00] big, big fire. And that requires the fact that the ceiling is flammable and that you have a leading edge in the ground fuel and a trailing edge in the ground fuel. And you have, again the same on the ceiling because the ceiling a leading edge and a trailing. It, it means that we are thinking of bringing a new model of traveling fires that brings into account what happens also to the ceiling.

[00:57:23] Wojciech Wegrzynski: This little details that completely changed the complexity of the problem and really make you appreciate the world of fire science. We had this moment in a recent experiment where we were very happy with, our, let's say, predictions of what will happen in a small compartments.

[00:57:40] Wojciech Wegrzynski: Then we've put a beam into the compartment and then change everything. And it was like, what a great time to be a fire scientist, whatever, like this tiny change has changed things completely,

[00:57:51] Wojciech Wegrzynski: So for the last question, and it's also, in a way an appreciation, not all of these experiments or the recent one, at least , I see ARUP being [00:58:00] heavily involved, which is an engineering company and, they don't sell compartments obviously, and they don't sell anything yet.

[00:58:08] Wojciech Wegrzynski: They, they seem to be, uh, funding this, this research and, and promoting the methodology and, and, are very active in development of that. And I think in a way, your collaboration with them on this project is in a way a model, a lot of interesting questions could have been answered in, in fire engineering world.

[00:58:26] Wojciech Wegrzynski: So how did you convinced a commercial company that does not have a direct economical interest , in pursuing, such in program to so heavily invest in that and convince them that it's for the better.

[00:58:39] Guillermo Rein: So the professional relationship that my group has with ARUP is the most beautiful thing that I've been involved with. I've been working with Arups since I arrived to the UK, literally I met them within months, within weeks of arriving to Scotland when I was in Edinburgh. And since then I've created a partnership that just keeps growing and [00:59:00] growing and growing, in three things that I want to highlight, the first one is there were very early believers

[00:59:06] Guillermo Rein: at this point, it was believing in the concept of traveling fires. Whereas most people in the community were saying, you're crazy what you're talking about. And very often you are wrong. And yet, uh, ARUP said that is very interesting. , how can we help you? So you develop these farther. Let's see what are your findings?

[00:59:23] Guillermo Rein: And they funded. The PhD of Jamie Stern Godfried, which was an engineer in Arup. That led to add up to be the first engineering company in the world that used traveling fire in a real building. That's a major thing, right? It goes from the paper or the PhD thesis to a real building. I mean, as a scientist, I still impressed that that is happened.

[00:59:44] Guillermo Rein: And then that'll develop this in more of their buildings and their, the competitors started to pay attention to this. And when they were asking to add up, what is this travelling fire thing ARUP was, actually given them a copy of a thesis of Jamie's Stern Godfried. They said, well, you, you will read everything about it here in this, the [01:00:00] thesis.

[01:00:00] Guillermo Rein: So ARUP was not only just key in sponsoring the research, he was an early adopter and he was a key agent in the spread of traveling far methodology, all across England. He was first, then he was in Scotland. It was also in the middle east, of. And it was also in Canada and even United States now is thinking of doing it right.

[01:00:19] Guillermo Rein: Without ARUP nothing like this would have happened for many, multiple reasons. Also ARUP has been a major, company hiring my PhD students. Literally every single piece of student except Heidari. Mohammed were hired but ARUP immediately right after and many other ones.

[01:00:34] Guillermo Rein: So that creates an interface between the research and engineering. The fact that ARUP is able to put, the scientists to work as engineers right away. And the third one is that they it's not that they were involved with that they let they design and they justify and they find the money to the experiment that I told you that happened in France, this replica of Obora with, uh, CLT and glulam in timber

[01:00:58] Guillermo Rein: um, it is not [01:01:00] that I convinced them in this case. It was actually, they did it. They knew how to do it, and they just invite me to help them and to be involved in the decisions and the details of how to do it. So , for these three reasons, the relationship that we have with ARUP is incredible, very important for my career without ARUP I I'm, I might not be here today in interview in your podcast.

[01:01:21] Wojciech Wegrzynski: The fact that an engineering company was there from the start. I was trying to use the abstract idea in real engineering in a way better testing the usefulness of this model. If the model was too slow or not reliable, they would tell you, and you would know, and you could apply changes.

[01:01:35] Wojciech Wegrzynski: I think without this, , collaboration, it would have just ended as a beautiful idea or, or a beautiful model that would be put on the shelf. Like it happened with many models and in my own engineering, I also solve issues that are key for my own engineering and the engineering of my colleagues at the office.

[01:01:52] Wojciech Wegrzynski: And, uh, and these things happened to be important for many engineers over the world. So I really cherish , this, uh, this model collaboration and , [01:02:00] between your, scientific unit and an engineering company. And, I'm very happy to see many other engineering companies. It's not that they start there.

[01:02:07] Wojciech Wegrzynski: There are many companies that invest in science, and I think , this is a key in building a safer future for us all. So, with this, kind accent, thank you so much for being here again. I hope it's not the last time for you at the Fire Science Show that there is at least 37 other topics that we need to cover in the podcast. So I hope we'll get through that.

[01:02:28] Guillermo Rein: Thank you Wojciech. It's always a pleasure to talk to you and you just give me a call when, when, whenever you went to hear a Spanish accent, from London.

[01:02:35] Wojciech Wegrzynski: My artificial intelligence translator is not a huge fan, but we can, we can handle that. It's much worse with italians really. Don't worry. Thank you. Thank you so much for being here and, see around Guillermo

[01:02:48] Guillermo Rein: again, take care. Bye bye.

[01:02:50] Wojciech Wegrzynski: Thank you so much, Guillermo, both for this episode and discussion and for your enthusiasm and support to the podcast. That's much appreciated.

[01:02:58] Wojciech Wegrzynski: I hope you've enjoyed this [01:03:00] talk about traveling fires, you have probably have had a lot about them in the past. But I think in this podcast, episode, Guillermo shared some stuff that I personally never heard. So I'm very happy. I've learned something new today and, traveling fires that are very close to my heart.

[01:03:15] Wojciech Wegrzynski: I've been there at the experiments. I've done some experiments myself, actually tomorrow I'm presenting my first results from my own furnace traveling, fire experiments. And I'm really excited about that. So I truly believe in this methodology. And I think in this episode, I really enjoyed that. It was quite focused on engineering and practicality. I mean, it's obviously important to understand the physics of fires and, absolutely fundamental to know how they grow, how they move, how they decay, because without that knowledge, we're unable to predict them and fight them. However, I really enjoyed what Guillermo did at his time at Edinburgh and now at Imperial, he's continuing that is that he recognizes the limitations of [01:04:00] engineering and he's trying to produce science that's really useful to us engineers and trying to find ways how to model this fires in a way that is compatible where the ways we are modelling our fires today. So I think there's a great achievement to, to seek, fire theory that is so complex yet so useful. We know that there are many approaches to traveling fires. There's much, much research. I'm being, carried over the world. I'm actually going to try and link the research and know about traveling fires that I've seen in literature by Edinburgh, by Queensland, phenomenal papers by Hidalgo and all others from this, uh, large tall building experiment that Guillermo mentioned and, recent developments from Arcelor Mittal and other collaborators in their travelling fire project. And I hope some of this will be useful. Uh, we know that method is already useful today, but it can be better. And as Guillermo mentioned, it's growing, it's developing and all the knowledge that we gained from all over the world can [01:05:00] be added to this, to create an emerge new, better ways of designing and creating a bit safer world.

[01:05:07] Wojciech Wegrzynski: And, that would be it for today's episode. Thank you so much for being here for listening to it. I hope you've enjoyed it. It's usually next week and other really good episode.

[01:05:18] Wojciech Wegrzynski: And I'm super excited about the next week's episode, I've talked about AI, for the third time in the podcast. And for the third time, it was a fantastic experience. And once again, I'm convinced that this is kind of the future of fire science and engineering. So, if you would like to see the future, , join me next Wednesday and yeah, take care, See you soon!