Forecasting fire dynamics: tomorrow's infrastructure protection

Imagine a technology able to forecast fires. It would lead to a paradigm shift in the response to emergencies and provide the Fire Services with essential information about the ongoing blaze with some lead time (i.e. seconds or minutes ahead of the event). It would also allow for the future of infrastructure protection to be implemented in smart buildings.

316 s after ignition. could this be forecasted ahead of time? [Rein 2012]

But despite advances in the understanding of fire dynamics over the past decades and despite the advances in computational capacity, our ability to predict the behaviour of fires in general and building fires in particular remains very limited. The state-of-the-art of computational fire dynamics is not fast or accurate enough to provide valid forecasts on time...

Paleofuture: forecast made in 1900 of the fire-fighting in the year 2000.
By Villemard, 1910, National Library of France

But we found a way to solve this problem. In a recently finished PhD thesis and set of published  papers, we show the technology is possible. We  propose to use sensor measurements of the ongoing fire to steer and accelerate computer simulations. This takes advantage of the concept of data assimilation (similar to what meteorologists do to forecast the weather).

Our method consists on combining a simplified spread mechanism with a fire model, and use sensor data to find the fire parameters that dominate the spread. This way, the model automatically recovers information lost by approximations in the physics, chemistry and the maths.

Concept of data assimilation and the sensor steering of model predictions [Cowlard et al 2010]

 A series of compartment fire cases haven been studied this way, and we investigated two different fire models. First a simple two-zone model, and then a state-of-the-art computational fluid dynamics (CFD) model.
 
For the simple two-zone forecast model, the firepower and the growth rate were estimated correctly up to 30 s ahead of the event: the model was faster than the fire. This was the very first time a fire forecast technology was demonstrated and the first time positive lead times were reached. The results show that the simple model is able to deliver fast and useful information about the ongoing fire thanks to the sensor data. This initial work demonstrated that the new methodology is effective, and allowed us to move to the next level of complexity. 

Computational domain of the fire
compartment [Jahn et al 2012]

For the CFD forecast model, we use a coarse grid that provides short computation times. Spatially resolved forecasts were obtained in reasonable time. It is even possible to estimate the growth rates of several different spreading fires simultaneously. Although actual positive lead times were not reached here with CFD, it is shown that the use of relatively coarse grid size in the forward model significantly accelerates the assimilation (up to 100 times faster) without loss of forecast accuracy. Actual positive lead times with CFD are possible by reducing the computational time by at least another order of magnitude in the near future using high performance computing techniques.

Dalmarnock Fire Test One conducted on July 25th.

Our latest bit on the topic was a test case using the measurement data  from a real fire. We forecasted in near real time the Dalmarnock Test One, conducted in 2006 inside the 3.5 x 4.7 x 2.4 m living room in a high rise building in the city of Glasgow. It was possible to find a good fit between the observations and the forecast using CFD.


The results are a fundamental step towards the development of forecast technologies able to lead the fire emergency response. The work opens the door to forecasting fire dynamics, but it is an on-going research topic.

We are happy that the work has been featured in the media and  people is being exposed to this novel idea:

• Interview for Scottish TV News (go to minute 19 here). Aired on 29 Nov 2010.
• Interview for BBC Radio Scotland (or go minute 42.20 here).  Aired on 29 Nov 2010.
• Articles in CORDIS-EU and Xinhuanet (in Chinese).

Our research resources on the topic (in reverse chronological order):

1) Jahn, Rein and Torero (2012), Forecasting fire dynamics using inverse
Computational Fluid Dynamics and Tangent Linearisation, Advances in
Engineering Software 47 (1), pp. 114-126. doi:10.1016/j.advengsoft.2011.12.005

2) Rein (2012), Plenary Keynote: Numerical forecasting of fire dynamics: tomorrow's infrastructure protection - Young Investigators Conference of the European Community on Computational Methods in Applied Sciences (ECCOMAS), Aveiro. See below.

3) Jahn, Rein and Torero (2011), Forecasting Fire Growth using an Inverse CFD Modelling Approach in a Real-Scale Fire Test, Fire Safety Science 10, pp 1349-1358, doi:10.3801/IAFSS.FSS.10-1349 

4) Jahn, Rein and Torero (2011), Forecasting Fire Growth using an Inverse Zone Modelling Approach, Fire Safety Journal 46, pp. 81–88. doi:10.1016/j.firesaf.2010.10.001. Paper shortlisted for 2010 Lloyd's Science of Risk Prize.

5) Jahn (2010), Inverse Modelling to Forecast Enclosure Fire Dynamics, PhD Thesis, School of Engineering, University of Edinburgh.

6) Cowlard, Jahn, Empis, Rein and Torero (2010), Sensor Assisted Fire Fighting, Fire Technology 46 (3), doi:10.1007/s10694-008-0069-1


Numerical forecasting of fire dynamics (Plenary YIC ECCOMAS)

Brunel y Martinez

Carta envida hoy al director del periódico El Mundo.

--------------------

Sr. Director:

¿Martínez?. Fuente: Wikipedia

El artículo recientemente publicado en su periódico y que firma Luis Martínez ("De 'Trainspotting' a 'Disappointing'", 28/07/2012) ignora valientemente quien es uno de los personajes más importantes de la historia de la humanidad. En referencia a ceremonia de apertura de los Juegos Olímpicos de Londres, el artículo dice " ¿De qué se reiría Brannagh con su muy shakespeariana apostura? ¿De explotar a los pobres campesinos (él 'hacía' de empresario, dedujimos)"

Durante la ceremonia, el actor Kenneth Branagh hacia el papel de Isambard Kingdom Brunel (1806-1859), ingeniero durante la revolución industrial y uno de los personajes británicos más importante de todos los tiempos. Es relativamente normal que en España no se sepa mucho de Brunel, dada la poca importancia que tienen la ciencia y la tecnología en el país, pero lo peor es la asociación automática y trivial con la explotación de campesinos.  Sin Brunel, el Señor Martínez no existiría, o sería un campesino, y El Mundo sería muchísimo más pequeño.

Referencia: http://es.wikipedia.org/wiki/Isambard_Kingdom_Brunel

Guillermo Rein

Edimburgo, Reino Unido

Interview on the accidental burning of ancient carbon

I have been interviewed for GeoLog, the blog of the European Geoscience Union (EGU):

Geotalk: Dr Guillermo Rein

It  features my research on smouldering combustion, the largest fires on Earth and the accidental burning of ancient carbon. It is released as the first interview in the new monthly blog column called Geotalk, featuring short interviews with scientists about their research.

Dr Rein next to a water vapour vent on top of the 30m-high Bogside bing, near Glasgow, Scotland. This bing is a man-made hill of mining waste, and started to smoulder in 2009, approximately 80 years after the closure of the pit. The spread of the combustion is accompanied by the development of vents ahead of the front. (Image by Dr Ricky Carvel and Dr Guillermo Rein, distributed under a CC BY-SA Creative Commons licence)

Smouldering fire of organic soil in Oregon National Wildlife Refuge

The dry organic soil in Malheur National Wildlife Refuge has ignited and several smouldering hot spots have been burning since last week. They were started by the flaming Miller Homestead wildfire on the evening of July 12 but the smouldering fire is now slowly self-spreading.

Suppression attempts are under way by the Fire Service including local flooding and compartmentation. It is essential to act quickly. Under dry conditions as the ones currently present in Oregon, smouldering fires can last for months, releasing large quantities of old carbon stored in the soil.

Smouldering organic soil after the Miller Homestead Wildfire moved onto the refuge the evening of July 12. Photo Credit USFWS.

Workshop on Smouldering Wildfires and The Earth System

I Workshop on Smouldering Wildfires and the Earth System

at University of Edinburgh, King's Buildings

Fri 27 July 2012, from 9am to 1:30pm.

Taking advantage of the visit of a few brilliant researchers working on smouldering wildfires, I am organizing a small workshop on the topic for Friday 27 July to bring together fire dynamic, engineering and geosciences. Small, but the first of its kind. It is focus mostly on peat lands, but other ecosystems and fuels are welcome (eg, coal, organic soils, litter). All are invited (no fees), and interdisciplinary backgrounds and topics are specially welcome. If you want to attend or give a talk, please send me an email to G.Rein@imperial.ac.uk.

Some smouldering peat experiments will be conducted in the lab on Thursday afternoon. Workshop attendees are invited to join us to witness/help with the tests.

See google map here to the venue, Seminar room in the 3rd floor of Alexander Graham Bell Building, University of Edinburgh, King's Buildings campus.

"Smouldering fires, the slow, low-temperature, flameless burning, represent the most persistent type of combustion phenomena, and leads to the largest and oldest fires on Earth. Indeed, smouldering megafires of peat occur with some frequency in for example North America, Siberia, the British Isles and South-East Asia during the dry session. Smouldering fires propagate horizontally and vertically through organic layers of the ground and can reach very deep where large cracks or natural piping systems exist. This threatens to release ancient carbon stored deep into the soil. Once ignited, they are particularly difficult to extinguish despite extensive rains, weather changes, or fire-fighting attempts, and can persist for long periods of time (months, years, or even centuries), spreading into the ground and over extensive areas." from the chapter Smouldering Fires and Natural Fuels, 2013, written by G Rein for an incoming Wiley book "

Fire Phenomena in the Earth System – An Interdisciplinary Approach to Fire Science".

UPDATE: Incidentally, I have just been interviewed for GeoLog, the blog of the European Geoscience Union, on smouldering fires and accidental burning of ancient carbon.

Final Programme (click on title to see pdf of presentation slides):

- Dr Guillermo Rein from Imperial College London (UK) to give an overview of smouldering fires on the Earth System.
- Dr Rory Hadden from University of Western Ontario (Canada) to talk about carbon emissions from smouldering fires.
- Dr Matt Davies, University of Glasgow (UK) to talk about peat fires and ecology in Scotland.
- Dr Adam Watts from University of Florida (USA) to talk about the role of fires in tropical wetlands.
- Nuria Prat from University College Dublin (Ireland) to talk about postfire effects of smouldering peat in a boreal pine forest.
- Dr Haixiang Chen from State Key Laboratory of Fire Science (China) to talk about computational modelling of smouldering fire.
- Dr Jon Yearsley from University College Dublin (Ireland) to talk about celullar automata modelling of peat fires.
- Keith Torrance from University of Strathclyde (UK) and University of Alaska (USA) to talk on smouldering coal heaps in Lanarkshire, Scotland.
- Dr Christine Switzer  from University of Strathclyde (UK)  to talk about the chemical and physical changes induced by smouldering on inert soil samples.

Tilbury smouldering fire

Update on the 2012 Tilbury biomass fire (which was discussed in Feb this in blog). RWE officials have now confirmed to the press that the fire was caused by self-heating of biomass pellets leading to a smouldering fire:  "it is likely that the increased levels of oxygen caused the ignition of the smouldering dust" [Utility Week].

Just to note that the wording used by RWE is not the most fortunate. It was not the oxygen which caused the fire, but the thermal conditions used to store the biomass pellets (too large piles and/or poor ventilation, etc). 

Geoengineering and Burt Rutan - The Economist

Letter to the Editor of The Economist sent on 6 of June 2012.

----


Dear Sir,

SpaceShipOne (designed by Mr Rutan)
at the National Air and Space Museum, Washington D.C.
Photo from wikipedia.

In your last Brain Scan article ("A maverick in flight", Technology Quarterly, June 2012) on the accomplishments of Burt Rutan, a pioneering and unconventional aerospace engineer, I find entertaining how Mr Rutan uses acrobatics to announce that global warming will lead environmentalists into an engineering breakthrough. He refers to unprecedented global warming and the tipping point for atmospheric carbon dioxide as "it’s just nonsense".

But this might not be a pejorative term for him. The statement is followed by the clarification:
 "You run into them [breakthroughs] when you’ve found something that doesn’t make sense and you find a way to make it work".

Maybe he is announcing the arrival of geoengineering. I would approve.

Best Regards,

-
Dr Guillermo Rein
Senior Lecturer in Mechanical Engineering
Imperial College London
http://www.eng.ed.ac.uk/~grein

Safety disadvantage of Plastic houses

Letter to the Editor of The Independent. Sent on 22 Jun 2012

----

Dear Sir,

EFTE roofs used in the Eden Project (wikipedia)

In your article "Here's one I won earlier" (21 Jun 2012), Alex Aldridge describes the winning idea of "Plastic houses" (eco homes with ETFE roofs) at the European Inventor Awards. He mentions its three main advantages (energy efficiency, blasts resistant, and light weight) but only two minor disadvantages (easy to cut through, noisy in rain).
He forgot to mention the most important of the disadvantages that happens to cancel one of advantages: while EFTE might be suited to resist terrorist bomb blasts, it definitely cannot resist fire. Moreover, it feeds to it as EFTE is a flammable material.

This brings bad news to plastic housing from a safety perspective.

Best Regards,
Dr Guillermo Rein
Senior Lecturer in Mechanical Engineering
Imperial College London
http://www.imperial.ac.uk/people/g.rein

Inside peer review: a (top science)^3 case

I just found a very interesting exercise of transparency in peer review on a top scientific topic (climate change) in a top scientific journal (PNAS) by a top researcher (Prof Lindzen, MIT). Note that Prof Lindzen portrays a minority scientific view, he thinks climate change forecasts are uncertain and might be overestimating warming:

 

 "Lindzen-Choi ‘Special Treatment’: Is Peer Review Biased Against Nonalarmist Climate Science?" by Chip Knappenberger. June 9, 2011.

I found this after reading the NYT article "Clouds’ Effect on Climate Change Is Last Bastion for Dissenters" by J Gillis, April 30, 2012.

Disclaimer: I post this becuase it is a very interesting and unique case of how peer review works inside a top journal (for good and for bad). This does not mean I support Prof Lindzen's scientific work (my expertise is in fire dynamics).

What is a flame?

The Flame Challenge is a competition set up online by actor Alan Alda to explain the science of a flame to a jury of 11-year-old students. Quite a science communication task. The winner (and six finalists) were announced recently: congratulations to Ben Ames, University of Innsbruck. This is his winning video:

 

The science content is spot on, and the format of the explanation very original. If you have an 11-year old nearby, ask to confirm the appeal of the entry. It looks very convincing to me but I am 2.36 times too old for that. Well done Ben.

The organizers are now asking kids age 10-12 to propose the next question for the Flame Challenge. Stay tuned.

This reminds me of the famous lectures of Faraday given in 1860's to kids/juveniles in London on a very similar theme, The Chemical history of a Candle.

Biomass self-heating fire in Tilbury Power Plant?

The Tilbury Power Plant (Essex, UK) suffered a large fire on 27 Feb 2012 [BBC]. The blaze involved two fuel storage units and led to the immediate closure of the plant. The blaze was controlled in one day by a crew of about 120 officers from the Fire & Rescue Service. The plant will not be fully functioning again until June. RWE, the owner of the plan, said direct damages have been estimated to cost around €4m. The losses for business interruption would be in addition to this.

July 2012 UPDATE:  Since the end of June, and as planned, two units are back to normal operation at Tilbury. The rest of units are expected to be working in one month time. More importantly, RWE officials have now confirmed to the press that the fire was caused by self-heating of biomass pellets leading to a smouldering fire:  "it is likely that the increased levels of oxygen caused the ignition of the smouldering dust" [Utility Week].

Nov 2012 UPDATE: The largest power station in the UK, Drax, is ready to burn biomass too. They are building four giant domes to store the fuel, about 30 m tall each. I am not familiar with the internal divisions of these domes, but I note that it seems well above the critical self-heating size, specially during summer time. See the domes in this video of the BBC.

Panoramic of Tilbury Power Plant before the fire. Photo from www.rwe.com

 Tilbury Power Plant during the fire (2012). Photo from East News/www.mirror.co.uk

 
Tilbury was a ~1100 MW coal-fired power plant buitl in 1969. Now it is one of the biggest and most environmentally-friendly combustion power plants in the world after having gone a partial reconversion to biomass burning (750 MW, biomass shipped from the US [The Guardian]). The conversion aimed to "prove that sustainable biomass can play a role in long term carbon reduction, it is crucial to test the technology on large-scale" [RWE]. It was just about to star operations of these new facilities when the fire took place.

I look forward the results of the ongoing fire investigation to identify the cause and origin, but I could not avoid jumping into some some early conjetures.

The fire started in the new biomass storage units where fresh loads of biomass had been stored for the first time (~6,000 tons of biomass pellets). This strongly hints to self-heating as the most probable cause. Self-heating refers to the tendency of certain materials, like biomass pellets and coal, to spontaneously heat up and smoulder at ambient temperatures. This can result in a spreading fire without intervention of any external heat source. The topic is one of my fields of expertise. Power companies know well how to avoid self-heating of coal piles (small stockpiles, ventialtion, quick turn overs) but when a new reactive solid is stored (in this case biomass) the problem can go undetected until the accident takes places. This is the price of innovation. Several types of biomass pellets are known to be more reactive at low temperatures than coal. And this would not the first time that the hazard has been underestimated by applying coal self-heating standards to biomass storage.

Unfortunately, all the biomass involved in the fire was burnt and none of the heat could be used for power or human comfort. The associated pollution (CO, VOC, PAH) and CO2 reached the atmoshpere wihtout giving us any of the potential benefits. Thin favour to sustainablility.

Smouldering fire of large compost heap in Havelock

After Hurricane Irene made landfall on Aug 27, 2011, the city of Havelock in North Carolina (USA) decided to shred all damaged trees and vegetation and collect them in a large heap. The resulting biomass stockpile was ~4000 m^3 in volume, the equivalent capacity of a 16 m cube. The idea was to produce plenty of free compost for the city.

But as the heap dried and decomposed, on its way to become compost, it also started to self-heat and a smouldering fire was initiated without any external source. All organic porous media is known to self-heat under the right environmental conditions of low moisture, poor ventilation and large stockpiles, and these were met in the Havelock heap. Havelock News reports that the fire was first detected on Jan 17, 2012, probably becuase of large and visible off-gassing. This means that the first hotspots formed several weeks before that, maybe during early Fall. After it was detected, the Fire Havelock Fire and Rescue Department and the US Forest Service were called in. They dosed large amounts of water and spread the heap material over a wider area to quench the fire. And it worked, so far. But hotspots deep into the heap are going to be very difficult to cool down completely.

A bulldozer spreads out the pile of smouldering biomass in Havelock. Photo by Drew C. Wilson/Havelock News.

Self-heating
In this poster that I presented recently, I explained self-heating as follows:

"Self-heating refers to the tendency of certain reactive solids in oxidative atmospheres to spontaneous exothermic reactions at low or ambient temperatures. This is a well known problem for industries transporting and storing porous carbon-rich materials [eg, peat, biochar, coal, char and most organic powders]. Initially, small amounts of heat are released and accumulate during longer times when heat losses are low (eg, large stockpiles, high ambient temperatures). This results in a sustained increase of temperature without any external heat source. Above a certain temperature, the process self-accelerates and leads to thermal run away. For example, Semenov’s Ignition Theory describes mathematically the process as controlled by heat generation and heat losses"

Mititating Actions
The main culprit in the case of the Havelock heap seems to be its large size. In other to prevent self-heating events, stockpiles must be kept below a certain critical size. The fact that the fire was detected in winter time when ambient temperatures are low (between -1 and 10 C), testifies to the strong reactivity of the biomass heap. But there are other contributing factors. In order to mitigate the risk of self-heating fires, heaps ought to be designed complying with the following principles:  

*Stockpile size: As the size of the pile is made smaller, heat losses increase and the risk of self-heating is reduced. The maximum safe stockpile size is given by the ambient temperature and reactivity of the material.  *Wetting: Material with large moisture contents do not ignite.  
*Ventilation: Add design features that enhance natural ventilation and cooling.
*Inertation: Reduce reactivity by mixing the biomass with inert material like sand (see here).

Where these observed in this case?

Computational model of new clean-up technology

We have just published a paper in the journal Environmental Modelling & Software reporting our computational model of the combustion technology that cleans soils (EMS 2011, in press). Based on the physics of the problem, the model simulates the destruction of industrial chemicals found extensively polluting the subsurface and aquifers.

This very promising remediation technology is called STAR (Self-sustaining Treatment for Active Remediation) and was developed and patented at the University of Edinburgh. The BBC described it as "It burns away pollutants such as oil and petrochemicals from the ground, but leaves the original clean soil behind" [New clean-up technology trialled, 2010]. It consists on boring the site at a few strategic locations, and inserting at some depth a source of heat (igniter) and a source of oxidizer (air injector). The smouldering combustion front is initiated by the igniter, and the rate and location of the front is controlled by the injectors. Even compounds that are resistant to biodegradation are effectively destroyed by STAR. The latest pilot test was conducted at a former cresol manufacturing facility in New Jersey. It demonstrated the rapid rate of contaminant destruction and the high remediation efficiency (95 to 99.99%), with an measured sustained destruction rate up to 800 kg/day.

STAR relies on the principles of smouldering combustion of liquid fluids impregnated in porous media. Schematic from Siremlab.

The model is two dimensional (subsurface slices, vertical and horizontal) and combines a simulator of  airflow through the soil with calculations of the propagation of the smouldering combustion front. The propagation component  is based on a fire growth simulation, the same principle used in some wildland fire models like FARSITE. The model handles well the most challenging physical scenarios of heterogeneous soil composition and multiple contaminated spots (see second figure below). The results show that air permeability, which affects the movement of the injected air, is a dominant factor for the spread rate and shape of the combustion front.

Simulation with low permeability regions: (a) model domain set-up, (b) distribution of air (vector size range: 0.00–0.430 m/s) and position of the smoldering front 625 s (10.4 min) following ignition, (c) contour plot depicting the position of the smoldering front at 125 s (2.1 min) intervals from t = 0 s to 1500 s (25.0 min). (Figure 15 of the paper).

The model can now be used to optimize STAR and its deployment for specific contaminated sites. For example, to help finding the best location for injectors and igniters, or the most convenient distribution of multiple bore holes (eg, vertical, horizontal, staggered). 

Moreover, because the physical principles in the model are fundamental, it can be used to study other large-scale smouldering phenomena of importance like subsurface peat and coal fires.

STAR and smouldering combustion as a remediation concept are pending patent approval (UK Application 0525193.9 and PCT Application PCT/GB2006/004591, priority date December 2005). The full reference of the paper is:

S MacPhee, G Rein, J Gerhard, A Novel method for simulating smouldering propagation and its application to STAR (Self-sustaining Treatment for Active Remediation), Environmental Modelling & Software (in press), 2011. doi:10.1016/j.envsoft.2011.11.004