Sunday, 5 June 2016

ERC HAZE: Reducing the Burden of Smouldering Megafires

I am delighted to announce that I recently won a Consolidator Grant from European Research Council (ERC) for my group, Imperial Hazelab. With a total budget of €2m and 5 years ahead, I will be leading the project HAZE in Reducing the Burden of Smouldering Megafires: an Earth-Scale Challenge.


Dr Rein during a field trip making measurements
on an ongoing smouldering fire
.
Smouldering megafires are the largest and longest-burning fires on Earth. They destroy essential peatland ecosystems, and are responsible for 15% of annual global greenhouse gas emissions. This is the same amount attributed to the whole fleet of road vehicles worldwide (or 10 times the carbon footprint of the UK), and yet it is not accounted for in global carbon budgets. Peat fires also induce surges of respiratory emergencies in the population and disrupt shipping and aviation routes for long periods, weeks even months.

The ambition of HAZE is to advance the science and create the technology that will reduce the burden of smouldering fires. Despite their importance, we do not understand how smouldering fires ignite, spread or extinguish, which impedes the development of any successful mitigation strategy. Megafires are routinely fought across the globe with techniques that were developed for flaming fires, and are thus ineffective for smouldering. Moreover, the burning of deep peat affects older soil carbon that has not been part of the active carbon cycle for centuries to millennia, and thus creates a positive feedback to the climate system.

HAZE wants to turn the challenges faced by smouldering research into opportunities and has the following three novel aims:
  1. Conduct controlled laboratory experiments and discover how peat fires ignite, spread and extinguish.
  2. Develop multidimensional computational models for the field scale (~1 km) and simulate the real phenomena.
  3. Create pathways for novel mitigation technologies in accurate prevention, quick detection systems, and simulation-driven suppression strategies.
With this research project, Europe and Imperial Hazelab have the chance to lead the way and pioneer technologies against this Earth-scale and important but unconventional source of emissions.

Aerosol imaging by NASA of Oct 1997 showing the haze released by peat megafires in Borneo. 
Visual and overlaid infrared imaging of radial smouldering spread over a sample of peat ignited at the centre. See our original photo here.

Thursday, 2 June 2016

Welcome Yuqi and Franz to Imperial Hazelab

During 2015, Hazelab grew with two new PhD students who joined the Department of Mechanical Engineering, Yuqi Hu and Franz Richter.

Yuqi Hu is from China. He became a Safety Engineer from the China University of Geosciences in 2012 with a BSc degree, and then obtained an MSc degree from University Of Science and Technology of China in 2015. At USTC, Yuqi studied experimentally the small particles in the smoke of cigarettes. Now at Hazelab, the preliminary title of his thesis is "Experimental Investigation of Peat Fire Emissions and Haze Phenomena" and is funded by China Scholarship Council.
Franz Richter is from Germany. He became a Mechanical Engineering from Imperial College London in 2015 with a MEng degree. During this final year project, Franz studied computationally how the spread of non-uniform fires in a building affect the charring of timber structures. Now at Hazelab, the preliminary title of his thesis is "Computational pyrolysis of timber in fire" and is funded by EPSRC and Arup.

Monday, 16 May 2016

Radio interview on technology and the McMurray wildfire

Last week I was interviewed by Gareth Mitchell for the radio Click of the BBC World Service about the Fort McMurray wildfire in Canada. It is a short piece, just 3 min long, and it can he heard here. I was asked about the role of technology fighting wildfires, and I chose to highlight tankers, satellites, drones, and computer models. This is the text by BBC introducing the recording:
"The wildfire in Alberta, Canada, seems to be diminishing and residents should be able to return to the city of Fort McMurray over the next two weeks. The fire had appeared to be out of control just a few days ago but thanks to favourable weather conditions appears under control. The weather has played a huge part, but what about technology? AI, drones and satellites have all been used. Dr Guillermo Rein, from Imperial College, London and Editor-in-Chief of the journal Fire Technology explains how tech is now incorporated in fire management."
http://www.bbc.co.uk/programmes/p002w6r2

Friday, 29 April 2016

Fin's and Candle's Creative Contests

Engineering can be the most creative profession, but we engineers are in general not the best communicators nor the best at appreciating artistic work.

I always want to build on this issue and encourage a bit my engineering students' appreciation of communications and the arts. So this academic year, as in previous years, I started the courses with a Creative Contest, for both ME2 Heat Transfer, and IDX Combustion Science modules that I teach at Imperial College.

The instructions to participate were the following:

 "I have two extra copies of textbooks to give away. If interested, send me a poem, comic, drawing, painting, song, video, or anything creative that explains why you are taking this module. Art, wit and humour are allowed, even encouraged".
 
I show below the submissions. I was the sole jury and found two winners (the first two shown for each contest). Congratulations to the winners (I wish an extensive use your awards).


Fin's Creative Contest in ME2 Heat Transfer.




 

Candle's Creative Contest in IDX Combustion Science.







 

Previous years

2015 Fin's and Candle's Creative Contests in ME2 Heat Transfer and ME4 Combustion
2014 Fin's and Candle's Creative Contests in ME2 Heat Transfer and ME4 Combustion

Monday, 21 March 2016

The Fire Navigator: smoke and flame sensors in smart buildings

The Fire Protection Engineering magazine has recently published our article reporting exciting research on the theme of smart buildings and fire protection. In this work, sponsored by Chief Donald J. Burns Memorial Research Grant, my student Nahom and I developed an algorithm that uses data arriving from building sensors to detect and map an ongoing fire. The algorithm, called the Fire Navigator, then provides forecasts of future smoke and flame spread within the building, allowing to see where and how the fire would propagate if not stopped before hand.


We envision that the forecasting of fire dynamics in buildings will lead to a paradigm shift in the response to fire emergencies, providing the fire service with essential information about smoke propagation and flame spread ahead of time (i.e. minutes before it happens). Disposing of information on fire events before they actually happen would have a positive effect on the fire service efficiency and safety, therefore saving human lives and mitigating property losses and environmental damage. Smart buildings anticipate the occupants’ needs with the help of various sensors. Control of heating and air conditioning, energy consumption and lighting are now common examples of how sensors allow control over key aspects of the built environment. We want to extend this to fire safety engineering and enhanced fire fighting. Already existing smoke and heat sensors, as well as sprinklers, generate data that has yet to be harnessed and used in smart buildings. This is what our article proposes and shows how to do it.

Our work is based on combining new and old ideas. The new ideas are the use of a very quick fire model based on cellular automata theory, and the integration of  the whole system into building information models (BIM). You can read the full article at the SFPE website:

The Fire Navigator: Forecasting the Spread of Building Fires on the Basis of Sensor Data 


NOTE: This research was sponsored by SFPE and Bentley Systems via the Chief Donald J. Burns Memorial Research Grant. We thank Arup, specially Judith Schulz, for sharing their expertise in BIM and fire protection systems, and thank KPF for permitting the use of their architectural BIM models.

Thursday, 3 December 2015

Tackling the haze in South-East Asia: a call to COP21 Paris

Reprint of my original article published first in the blog of The Grantham Institute.

Peat fires are raging in Indonesia and their extent is staggering. The dry season is not over and NASA satellites have already counted more than 12,000 active fires, which have emitted in excess of 1.6 Gton of carbon dioxide equivalent. This is more than Japan’s annual emissions and close to the footprint of the whole of India. In fact, if peat fire emissions were considered, Indonesia would be the 4th highest emitting country in the world. With COP21 climate negotiations on carbon emissions due to start in just over a week, this widespread haze is choking the population and fauna.

Driven by energy goals and climate change, international efforts are moving towards reducing anthropogenic greenhouse gas emissions and limiting the burning of fossil fuels. However, by ignoring smouldering fires, a major source of greenhouse gases is being overlooked.

The long slow burn

Smouldering fire is a natural phenomenon that burns Earth’s organic-rich deposits, primarily peatlands, soils and coal. Sometimes termed smouldering megafires, these are the largest and longest burning fires on Earth and take place not only in Indonesia, but also in Siberia, Alaska, Florida and Australia to name a few.

Peat megafires destroy essential peatland ecosystems, and release huge quantities of carbon dioxide, carbon monoxide and methane, making up 15% of annual global greenhouse gas emissions. This is the same amount attributed to the whole of the European Union, or all the vehicles worldwide – and yet it is not accounted for in global carbon budgets.

Moreover, the burning of deep peat affects older soil carbon that has not been part of the active carbon cycle for centuries to millennia, and thus creates a positive feedback to the climate system (see Figure 1).
Figure 1. The peat fire problem at the Earth scale, including climate feedback. By G Rein, CC BY 3.0 license

Why so large?

Smouldering combustion is the slow, low temperature, flameless burning of porous fuels. It is sustained by the heat released when oxygen directly oxidises the carbon on the surface of organic soil particles. Once ignited, subsurface organic layers such as those in peatlands or carbon-rich soils burn slowly for long periods of time, spreading deep into the ground and over extensive areas.

Possible ignition events can be natural (e.g. lightning, self-heating, volcanic eruption) or anthropogenic (land management, accidental ignition, arson). Smouldering fires can be initiated by weak sources of ignition and are typically the most difficult to extinguish. Smouldering suppression requires much larger amounts of water than extinguishing flaming fires (it requires actual flooding of the land).

Easy ignition and difficult suppression make smouldering fire the most persistent type of combustion phenomenon on Earth. These fires burn for very long periods of time, lasting months, years, or even decades, despite extensive rains, weather changes and fire-fighting attempts. Peat fires have been active in Indonesia this season for the last more six months or more. They have become endemic in some areas of the world.


Figure 2. Visual and overlaid infrared imaging of radial smouldering spread over a sample of peat ignited at the centre. Photo by Rackauskaite, Huang and Rein (CC BY 3.0 license) http://blogs.egu.eu/divisions/sss/2014/10/01/soils-at-imaggeo-fire-watch-constellation


The Triple Challenge

Given the scale of the problem, relatively little action is being taken. I have identified three major challenges hampering global action:

Challenge #1 – Scientific understanding is poor: There are still large gaps in our knowledge of how smouldering fires ignite, spread or extinguish, which impedes the development of any successful mitigation strategy. Poor scientific knowledge on smouldering even leads to fatal misunderstandings and confusion between flaming and smouldering combustion.

Challenge #2 – Non-existent mitigation technologies: Smouldering megafires are routinely fought across the globe with techniques that were developed for flaming fires. These techniques are ineffective for smouldering fires because the heat transfer and the chemistry involved are completely different. For instance, aerial tankers do nothing to stop smouldering fires because flooding is required instead, and satellite monitoring substantially underestimates the size of peat fires because smouldering can spread underground.

Challenge #3- Topic fragmented among scientific disciplines: Smouldering megafires are an intrinsically multidisciplinary theme requiring collaboration by combustion scientists, ecologists, atmosphere scientists and biochemists.

These three challenges must be overcome before effective mitigation strategies can be implemented. While the largest fires on Earth continue releasing naturally stored carbon into the atmosphere, we are failing to protect both people and the planet.

A Call to Paris

We can reduce the worldwide burden of smouldering megafires and create new technology drivers by pursuing greater experimental understanding and up-scaling our research in the field.

Science is an essential enabler of understanding of peat fires. By strengthening the importance of fundamental knowledge and by consolidating the disciplines interested in the phenomenon, I believe combustion science will serve as the basis for tackling wildfires.

COP21 in Paris has the chance to mobilise the resources needed to advance the science that can lead the way and pioneer technologies against this Earth-scale but unconventional source of emissions.

Further Reading

Tuesday, 27 October 2015

Our Student at the Royal Welcome of Chinese President

I was delighted to learn that my PhD student Xinyan Huang attended the Royal Welcome and Honour Guard Inspection held by Queen Elizabeth II for the Chinese President Xi Jinping. This is a traditional ceremonial welcome to foreign leaders visiting the UK. It took place last Tuesday near Buckingham Palace with the presence of senior royal family members and political leaders.

Xinyan was invited by Lord Chamberlain. There were 80 guests, 40 Chinese and 40 British. He was invited as one of three students representing the 150,000 Chinese students in UK. An important factor for being chosen for the honor is that Xinyan was the only student from Imperial College winning the 2014 National Award for Outstanding Chinese Student Studying Abroad given annually worldwide by the China Scholarship Council.
 
Xinhua media describes it like this: "With 41 rounds of gun salute fired from Green Park and 62 from the Tower of London, the Queen and the Duke of Edinburgh, bathed in rare London sunshine, formally welcomed Xi and Peng at the Royal pavilion on Horse Guards Parade".

Xinyan on the guest stage with the Honour Guard in the back.
Note: Xinyan is graduating from Imperial College soon and joins the University of California at Berkeley as a postdoc in the laboratory of Prof Fernandez-Pello.

Monday, 12 October 2015

Fire Science is in Season

Article reprinted with permission from the Combustion Institute
 
by Guillermo Rein, Imperial College London, UK
and Naian Liu, University of Science and Technology, China


Wildfires in the United States this season are raging in California and other regions. Thousands of people have been evacuated from their communities, their homes lost. Millions of hectares of forest have burned. Countries in the southern hemisphere such as Australia and South Africa are preparing for what government agencies expect to be a severe brushfire season. Billions of U.S. dollars are spent annually around the world to fight wildfires. Particularly large firefighting budgets are approved in the United States, Australia, Canada, China and the European Union.

But let’s start with the broad context to the wildfire problem borrowing ideas from (Rein 2015). Fire is a natural phenomenon. It contributed to shaping most ecosystems on Earth and plays essential roles supporting life through the regulation of atmospheric oxygen, the carbon cycle, and the climate. However, wildfire is also a hazard to life, and when it threatens human populations or valuable ecosystems, it must be suppressed.


Despite its central importance to the planet and to humanity, our understanding of fire remains limited. For example, we currently cannot predict the location of a fire in 30 minutes time. To quote Prof HC Hottel at MIT (1984): “A case can be made for fire being, next to the life processes, the most complex of phenomena to understand”. It comes as no surprise, then, that the discipline of fire science is less mature than other combustion topics.

Fire has been a topic of interest to the Combustion Institute since its foundation in 1954. For the combustion expert, wildfires are large-scale turbulent non-premixed flames fed by pyrolysis of a condensed-phase natural fuel. Historical contributions from combustion research have been especially important in understanding ignition and flame spread of natural fuels, flame radiation and emissions. Recent contributions include work published in Combustion and Flame or Proceedings of the Combustion Institute on flame spread over porous fuel beds (Liu et al. 2014), wildfire radiation (Cruz et al. 2011), forecasting wildfire dynamics (Rochoux et al. 2013), thermofluids of fire whirls (Lei et al. 2015) and heterogeneous chemistry of smoldering wildfires (Huang and Rein 2014).

Left: Flame spread experiment over an artificial inclined canyon. Photo by JR Raposo (Laboratory for Forest Fire Studies - LEIF, Coimbra, Portugal) 2014. Right: Combination of high-speed imaging shots shows the formation of a 1kW fire whirl under different angular speeds. Image by J Lei (SKLFS, China) 2014.


We must highlight the most recent contribution of combustion science to wildfires. The work of Finney et al. (2015) just published in PNAS is a scientific breakthrough. Finney et al. have discovered the long-missing piece of the puzzle to understand wildfire dynamics. For the first time, their work puts forward a fundamental, comprehensive and verifiable theory of flaming wildfire spread. Finney’s theory relates the rate of spread to basic fluid mechanics and heat transfer, and it is strongly supported by laboratory measurements and field observations. We expect Finney’s theory to have a profound impact in the field. Once implemented into a new fire spread model, the theory would improve predictions of fire behavior and help them gain in both accuracy and consistency. This in turn would allow the simulations used by the Fire Service worldwide to provide more reliable information for deployment and disaster management of fire incidents.

Combustion science is an essential enabler of understanding of wildfire dynamics. It is expected that by strengthening the importance of fundamental knowledge and by growing the fire community in the Combustion Institute, combustion science will serve as the basis for tackling wildfires.

References
  • MG Cruz, BW Butler, DX Viegas, P Palheiro, Characterization of flame radiosity in shrubland fires, Combustion and Flame 158 (2011) 1970–1976.
  • MA Finney, JD Cohen, JM Forthofer, SS McAllister, MJ Gollner, DJ Gorham, K Saito, NK Akafuah, BA Adam, JD English (2015) The role of buoyant flame dynamics in wildfire spread. Proc. Natl. Acad. Sci. USA, 10.1073/pnas.1504498112.
  • HC Hottel, Stimulation of fire research in the United States after 1940, Combustion Science and Technology, 1984, 39:1–10.
  • X Huang, G Rein, Smouldering combustion of peat in wildfires: Inverse modelling of the drying and the thermal and oxidative decomposition kinetics, Combustion and Flame 161 (2014) 1633–1644. 
  • J Lei, N Liu, L Zhang, K Satoh, Temperature, velocity and air entrainment of fire whirl plume: A comprehensive experimental investigation, Combustion and Flame 162 (2015) 745–758.
  • N Liu, J Wu, H Chen, L Zhang, Z Deng, K Satoh, DX. Viegas, JR. Raposo, Upslope spread of a linear flame front over a pine needle fuel bed: The role of convection cooling, Proceedings of the Combustion Institute 35 (2015) 2691–2698.
  • G Rein, Breakthrough in the understanding of flaming wildfires, Proceedings of the National Academy of Science 112 (32), pp. 9795-9796, 2015. doi: 10.1073/pnas.1512432112.
  • MC Rochoux, B Delmotte, B Cuenot, S Ricci, A Trouvé, Regional-scale simulations of wildland fire spread informed by real-time flame front observations, Proceedings of the Combustion Institute (2013), 34:2641-2647.

Monday, 21 September 2015

Travelling fire wins Best Fire Research Project by SFPE UK

We are delighted to announce that an Imperial-Arup team has won the Best Fire Research Project 2015.
The award, give by the UK Chapter of Society of Fire Protection Engineers and sponsored by H+H Fire was given to the project iTFM: Improved Travelling Fires for the Structural Design of Modern Buildings.
Team members were Egle Rackauskaite, PhD Student at Imperial College London, Guillermo Rein, Principal Supervisor at Imperial College London, and Panos Kotsovinos, Industrial Supervisor at Arup London.

The award judges said “Great piece of research with practical applications. Very interesting subject deserves more research in this area”.

The latest research paper on traveling fires was published in the journal Structures. And the work was also described at an Q&A interview published by the Press Office of Imperial College (see here).
Illustration of a travelling fire and distribution of gas temperatures.

Innovative architectural designs of modern buildings already provide a challenge to structural engineers. This is above all the case in structural fire engineering. However, most of the understanding and current design codes are based on the assumption of uniform fires in a compartment. In previous work, we have shown that fires in large, open-plan compartments, typical of modern architecture, travel from one part of it to another with non-uniform temperature distribution. These fires are referred to as travelling fires. And Travelling Fires Methodology (TFM) has been developed to account for the travelling nature of fires.


Our research also recently received a grant from SFPE to fund a summer collaboration with the group of Prof. Ann Jeffers at University of Michigan, Ann Arbor.

Sunday, 16 August 2015

PhD Studentship in Heat Transfer at Imperial College London

Applications are invited for a PhD studentship in the field of heat transfer and artificial intelligence funded by EPSRC and Arup.



2013 facade fire in Grozny. Photo from huffingtonpost
The research project, named INERSKIN, will develop a toolkit for fire safety optimisation of building façades. With a drive for thermally efficient buildings and sustainability, flammable insulation materials like polymers are more frequently introduced in the design of façades system. Because of the importance of façades and the increasing number of high rise buildings worldwide, it is critical that the interaction of materials and their performance in the event of a fire is understood, modelled and improved. INERSKIN will use artificial intelligence techniques and the state of the art of computational heat transfer to optimize their fire safety.

The student will join the Hazelab, the multidisciplinary research group led by Dr Guillermo Rein and part of the Thermofluids Division in the Department of Mechanical Engineering. The purpose of the group is to reduce the worldwide burden of accidental fires and protect people, their property, and the environment. To do so, Hazelab studies computationally and experimentally heat transfer processes, condensed-phase chemistry and thermodynamics of reactive solids.

You will be an enthusiastic and self-motivated person who meets the academic requirements for enrollment for the PhD degree at Imperial College London. You will have a degree in engineering or physics, and an inquiring and rigorous approach to research together with disciplined work habits. Interests in heat transfer and artificial intelligence are essential. Good team-working and communication skills are essential. Knowledge in fire science and building design are encouraged but not essential prior the project.

Candidates should fulfill the eligibility EPSRC criteria for stipend and fees (UK resident for at least 3 years). Please check your suitability at the following web site: http://www.epsrc.ac.uk/skills/students/help/Pages/eligibility.aspx

For further details of the post, contact Dr Guillermo Rein g.rein@imperial.ac.uk with up-to-date curriculum vitae.

Closing date: 30th April 2016.

Monday, 3 August 2015

Breakthrough in the understanding of flaming wildfires

I wrote a commentary article in the Proceedings of the US National Academy of Sciences (PNAS) about a recent stellar contribution to our understanding of how wildfires spread. In doing so, I have written in short the scientific context of wildland fires and also I put forward the possible impacts of the work on the field..
It can be read here ((10.1073/pnas.1512432112), and an except follows.

Breakthrough in the understanding of flaming wildfires

The rise of humanity was intimately bounded to fire. Humans first observed flames when fleeing wildland fires, the natural version of the phenomenon that would then become the most important technological achievement of the human race: the mastery of fire for cooking, lighting, settlement, hunting, and warfare (Bird 1995).
Wildfires are important to the natural sciences. Since deep time, the top surface of the Earth’s crust has been the interface where abundant plant organic matter meets an atmosphere rich in oxygen. This interface is flammable, especially in dry, windy and hot conditions, and leads to wildfire after an ignition event. Not only has fire contributed to shaping most ecosystems on Earth, but it plays essential roles supporting life through the regulation of atmospheric oxygen, the carbon cycle, and the climate (Bowmand et al. 2009, Watson et al. 1978).
As part of the current anthropogenic age, humans have also modified the fire regimes of many ecosystems, and have contributed for example to its cessation in certain regions (e.g., in the USA National Parks until 1960), or to increasing its frequency and severity through drainage (e.g., peatlands) and possibly through climate change (e.g., arctic fires). Of note, multiple US$ billions are spent annually across the world to fight wildfires for the protection of communities and valuable ecosystems.
Despite its central importance to the planet and to humanity, our understanding of fire remains very limited. For example, we currently cannot accurately forecast the location of a fire in 30 min time. To quote Hottel (1984): “A case can be made for fire being, next to the life processes, the most complex of phenomena to understand”. It comes as no surprise, then, that the discipline of fire science is less mature than other Earth science topics. For example, a quick look at the literature shows that there are three times more scientific studies published per year on volcanoes than on wildfires. Fire science requires more decades of fruitful research to mature and gain full understanding of this natural phenomenon.

Rate of Spread


The fate of a flaming wildfire starts with its genesis at ignition, by natural means like a lightning strike, or by anthropogenic means like slash-and-burn. Once ignited, part of the heat released by the flames will drive the spread over connected fuel beds of grass, shrubs, and trees. Another mechanism of propagation is by lofting burning embers that land farther away, but flame spread is more important. The dynamics of spread are such that wildfires accelerate with tail winds, dry weather, or up-slopes; and decelerate with head winds, rain or down-slopes.
The most lasting contribution to the science of wildland fires is the pioneering work of Rothermel in 1972 (Rothermel, 1972). He formulated an empirical model for predicting the spread rate of a wildfire. This formulation is ubiquitous and can be found at the core of most wildfire behaviour simulations. These simulations are currently in use by forestry agencies and firefighting command centres across the world. For example, Rothermel’s model is part of the US Wildland Fire Decision Support System, used in planning of every large and long duration federal wildland fire incident. However, Rothermel’s formulation is empirical: Whilst it can provide rough predictions of the rate of spread by calibration to previous laboratory data, it does not explain how fire spreads. Its empirical nature hinders scientific progress and does not allow for improvements to simulations. Until very recently, there was no valid scientific theory of wildfire spread that could complete Rothermel’s model.
Sketch of flame spread of a fire with tail wind over a fuel bed of fine particles. The paths for heat transfer by
radiation, convection, and flame contact are noted. According to Finney et al. (2015), the vortices are created by buoyant
instabilities and lead to ignition of the fuel by flame contact. Modified from Rothermel, 1972.

Finney et al. 2015


In this context, we see that the recent work of Finney et al. (2015) is a scientific breakthrough. Finney et al. have discovered the long-missing piece of the puzzle to understand wildfire dynamics. Their seminal work puts forward for the first time a fundamental, comprehensive and verifiable theory of flaming wildfire spread. Finney’s theory relates the rate of spread to basic fluid mechanics and heat transfer, and it is strongly supported by laboratory data and field observations across a wide range of scales from 10 cm to 15 m.

Let me put this in the framework of a simple theory. Fire dynamics dictate that spread can be seen as the succession of ignition events (Emmons 1963). This way, the rate of spread s of a fire is given in Eq. (1) by two terms, the length of fuel bed heated by the flames (expressed as δ) and the time that a fuel particle takes to ignite (expressed as tig) (Drysdale 2011).

 s=δ/tig   (Equation 1)

We know that mostly depends on flame inclination and the slope of the terrain, whereas depends mostly on fuel properties like particle size, moisture and plant composition. The scientific contributions of Finney et al. are cast around the novel identification of the two terms in Eq. 1 that govern wildfires.
First, by careful inspection of visual images of fire across scales, they show that vortex flows and peaks-and-troughs generated by the buoyancy of the flames are responsible for heating the fuel bed length δ. Then, temperature measurements then show that the intermittency of the peaks-and-troughs causes the flames to instantaneously touch the thin fuel particles, which in turn produces the contact ignition governing  tig. Figure 1 shows a sketch including these mechanisms.

Convection vs. Radiation



Their work feeds into a long-standing debate in the field on whether it is radiation or convection that controls the heat transfer to the fuel bed ahead (see Fig.1). The specific heat transfer mechanism affects the interpretation of experimental observations, and is critical in correctly formulating physically based models (Morvan 2011). Finney et al. settle the debate by identifying with strong evidence that heat transfer is controlled by flame contact, the phenomenon where both radiation and convection heat transfer are combined, but with the distinctiveness that the timing of flame contact is driven by convective flows.

Profound impact in fire science

Finney’s theory can have a profound impact in the field. The impact is four-fold regarding i) previous scientific studies, ii) wildfire simulations, iii) new technologies, and iv) multi-disciplinarity. These are explained in the following.
Previous scientific studies on wildfire spread should be revisited to help put Finney’s theory into a broader context. experimental and computational studies might need to be reinterpreted in the light of
the roles of flame intermittency and flame contact. The state of the art should naturally revisit and replace Rothermel’s model to give way to a new physically based Rothermel–Finney’s model.

Rothermel-Finney’s model would improve simulations of fire behaviour and help them gain in both accuracy and consistency. This in turn would allow the simulations to provide a more reliable layer of information during fire incidents.
The increased accuracy of simulations should eventually allow for high-fidelity forecasting technologies. A technology able to rapidly forecast the movement of a wildfire would lead to a paradigm shift in the response to emergencies, providing the Fire Service with essential information about the ongoing fire (Rios et al 2014).
The topic of wildfires is currently fragmented among the fields of biology, ecology, meteorology, chemistry, and combustion. These fields have a lot to offer one another, but better communication and cooperation are essential to move it forward. It is hoped that by strengthening the importance of fundamental knowledge and by settling long-standing debates, Finney et al. will serve as the basis for developing new multidisciplinary collaborations in the study of wildfires.

Finally, I foresee that after reading their work, many readers might start seeing the peaks-and-troughs reported by Finney et al. in every wildfire, as I already do now. As the English poet John Milton once said, “so easy it seem'd, once found, which yet unfound most would have thought impossible”.

References

  • MA Finney, JD Cohen, JM Forthofer, SS McAllister, MJ Gollner, DJ Gorham, K Saito, NK Akafuah, BA Adam, JD English (2015) The role of buoyant flame dynamics in wildfire spread. Proc. Natl. Acad. Sci. USA, 10.1073/pnas.1504498112.
  • MI Bird, Fire, prehistoric humanity, and the environment, Interdisciplinary Science Reviews 20(2), 141-154, 1995. DOI:10.1179/isr.1995.20.2.141A.
  • DMJS Bowman, JK Balch, P Artaxo, WJ Bond, JM Carlson, MA Cochrane, CM D’Antonio, RS DeFries, JC Doyle, SP Harrison, FH Johnston, JE Keeley, MA Krawchuk, CA Kull, JB Marston, MA Moritz, IC Prentice, CI Roos, AC Scott, TW Swetnam, GR van der Werf, SJ Pyne, Science 324 (5926), 481-484, 2009. DOI:10.1126/science.1163886. 
  • JE Watson, Lovelock, L Margulis, Methanogenesis, fires and the regulation of atmospheric oxygen, Biosystems 10 (4),pp 293-298,1978. 
  • HC Hottel, Stimulation of fire research in the United States after 1940, Combustion Science and Technology 39:1–10, 1984. doi:10.1080/00102208408923781.
  • RC Rothermel, A mathematical model for predicting fire spread in wildland fuels, USDA Forest Service, Intermountain Forest and Range Experiment Station, Ogden, Utah, Research Paper INT-115, 1972. 
  • HW Emmons, Fire in the forest, Fire Research Abstracts and Reviews 5, 163, 1963. 
  • D Drysdale, An introduction to fire dynamics, 3rd edition. John Wiley and Sons Ltd, Chichester, 2012. 
  • D Morvan, Physical Phenomena and Length Scales Governing the Behaviour of Wildfires: A Case for Physical Modelling, Fire Technology 47 (2), pp 437-460, 2011. doi:10.1007/s10694-010-0160-2. 
  • O Rios, W Jahn, G Rein, Forecasting wind-driven wildfires using an inverse modelling approach, Natural Hazards and Earth System Sciences 14, pp. 1491-1503, 2014. doi:10.5194/nhess-14-1491-2014

Monday, 27 July 2015

Improved travelling fires for structural design

The collapse of 1WTC, New York City, 10:28am Sept 11, 2001.
Photo by
9/11 Photos CC BY.
Our latest paper on travelling fires for structural design has been published in Structures (journal of IStrutE) with the title Improved formulation of travelling fires and application to concrete and steel structures.

Note: It is open access so you can read and share it without need for a subscription. We have posted in open access also our Matlab code to calculate the fire temperatures in zenodo.


Accidental fire can be disastrous, especially in buildings. The effect of fire on structural stability is critical in regard to safe evacuation and safe access for fire fighters, financial losses, and lost business. This is particularly the case in tall buildings where extended evacuation times are required due to phased evacuation practices. The World Trade Centre Tower fires in 2001 have highlighted the need of a more realistic design tools to represent fires in large compartments. 

Innovative architectural designs of modern buildings already provide a challenge to structural engineers. This is above all the case in structural fire engineering. However, most of the understanding and current design codes are based on the assumption of uniform fires in a compartment. In previous work, we have shown that fires in large, open-plan compartments, typical of modern architecture, travel from one part of it to another with non-uniform temperature distribution. These fires are referred to as travelling fires. And Travelling Fires Methodology (TFM) has been developed to account for the travelling nature of fires.

Illustration of a travelling fire and distribution of gas temperatures.
TFM was born in 2010 and offers a paradigm shift in the structural engineering of modern buildings. The concept has already been applied by engineering firms like Arup, BuroHappold or AECOM in the design of a dozen of iconic buildings in the UK (including the renovation of Battersea Power Station in London). TFM accounts for one of the fastest knowledge transfers from research to industry seen in fire protection engineering. TMF is now being studying in detailed in the USA for possible adoption as well.

The focus of this latest paper is on the improvement of the calculations of traveling fire (iTFM) to account for better fire dynamics, and the analysis of the effect on structural members. The proposed changes represent a simple yet powerful fire model. In particular, our paper shows that:
  • Using data from experiments and real fires, we limit the range of possible fire sizes thus reducing the time required for conduct TFM studies.
  • Analytical expressions are presented for generating time–temperature curves which are independent of grid size (previous versions of TFM) and can be easily calculated with any mathematical tool. 
  • Introduction of flapping term leads to reduced near-field temperatures for smaller fire sizes which cover a range between 800 and 1200 °C, as observed in real building fires. 
  • The location of the peak temperature in the compartment is found to occur at the end of the fire path (i.e. far half of the compartment from the ignition source).

Tuesday, 21 July 2015

Bosley explosions in wood mill

Last Friday evening, a crew of Sky News came home to interview me about the unfortunate explosions and fire in a wood mill in Bosley.You can watch the interview here.


Friday, 19 June 2015

Best Poster Award to reseach on the spread of peat fires

Congratulations to my PhD students from Imperial Hazelab Xinyan Huang and Francesco Restuccia for winning the Best Poster Award at the 2nd European Symposium on Fire Safety Science. Visiting student Michaela Gramola from University of Cambridge was also co-author. The work is an experimental study on how peat fires spread and lead to the largest fires on Earth.


 

Saturday, 30 May 2015

Research grant on travelling fires with Michigan

Egle Rackauskaite, PhD student
at the Imperial Hazelab.
I am delighted to announce that we have won a research grant from SFPE that will fund our summer collaboration with the group of Prof. Ann Jeffers at University of Michigan, Ann Arbor.

As we speak, my PhD student Egle Rackauskaite is at Ann Arbor working for the summer. She will use the SFPE Foundation Student Research Grant to continue the development of the pioneering design concept of 'travelling fires'.


Innovative architectural designs of new high rise structures already pose a challenge to engineers. This is above all the case in structural fire protection engineering. Understanding of fundamental mechanisms of whole building behaviour in fire has significantly increased in the last decades; however, most of this understanding is based on the assumption of uniform fires in a compartment. Recent work has shown that while the uniform fire assumption may be suitable for small enclosures, the large, open-plan compartments, typical of modern architecture, do not burn simultaneously throughout the whole enclosure. Instead, these fires tend to move across the floor plates as flames spread, burning over a limited area at any one time. These fires are referred to as travelling fires.


A travelling fire is a structural design concept that accounts for the spread of the flames along a large compartment. This creates two dynamic heating regimes to any structural element; the quick but intense heating by the direct impingement of the flames (near field), and the slow but limited heating by the smoke (far field).


Travelling fires challenge the design assumptions made in most design codes. Understanding the effects of travelling fires on structures is important for the development of modern cities with increased resilience to fire. Our work offers a paradigm shift in the structural engineering of modern buildings, and is directly impacting the way industry designs modern infrastructure and has already been applied to design a dozen iconic buildings in London, Manchester and Birmingham.

More information on travelling fires, see: