Fire Safety Engineering at Aalto

Since about two years, part of our team has been participating in planning and kick-off of the IAFSS Measurement and Computation of Fire Phenomena -working group on radiative heat transfer. This sub-broup was officially established in the third MaCFP meeting in Tshukuba, 2023.

The first activity of this group has been to prepare two benchmark simulation datasets using Particle Monte Carlo – Line-by-line modelling. Leading figures here have been Chandan Paul (now at NIST) and Prof Somesh Roy (Marquette Uni). I add below a snapshot of our recent poster in Combustion Institute meeting, presented by prof Fabian Brännström (Uni Wuppertal). These benchmark datasets were very recently published in Journal of Quantitative Spectroscopy and Radiative Transfer.

The idea of generating numerical benchmarks came from the observation that it is very difficult to perform detailed radiation measurements in fires or flames of relevant size. Also, when modelling the radiation phenomena, all the uncertainties of boundary conditions, fluid flow, turbulence, combustion, etc., will propagate to the radiation predictions and make it difficult to isolate the uncertainties that originate from radiation models themselves. By carrying out PMC-LBL and classical RTE solutions that are based on exactly the same scalar fields (temperature, concentrations), we should be able to isolate the sources of error.

Currently, we try use these datasets for validating non-gray gas phase radiation models for FDS. This work is carried out by Soroush Rashidzadeh in his doctoral thesis project. The FDS implementation will build on the analytical model comparison (also JQSRT), and the two-zone Turbulence-Radiation Interaction model, we published with Randy McDermott of NIST.

Posted by Simo Hostikka

Fire-stops are an essential component of buildings’ fire resistance. They are used for closing gaps between compartment boundary elements and as seals for cable and pipe penetrations. Many modern fire stop materials are based on polymeric materials, and for a basic fire protection engineer, it is difficult to understand why and how they can work. Why don’t they just burn away?

Also, building are designed for tens of years use, and the fire stops should be effective throughout the whole use period. Ageing of polymeric materials has been a hot topic of nuclear safety for many years, but there is little information on how the fire-stops perform when they get old.

If you are interested in characterizing commercial fire-stops, studying their ageing performance, and developing numerical models for their performance assessment, this could be your opportunity to get into academia. If you have a MSc degree and relevant skills, go ahead, read more and apply over here.

Posted by Simo Hostikka

Farid Alinejad defended his thesis in May 12th, 2023. The title of his thesis is “Modeling in-depth transfer of thermal
radiation in non-gray condensed materials”. Opponent was Prof Frédéric André from INSA, Lyon (now Univ Lille). Defense was successful and Farid has now graduated, and is already making career in research. Congratulations!

Farid’s work was extensive. The thesis was based on five published papers:

1. Alinejad, F., Bordbar, H., & Hostikka, S. (2020). Development of full spectrum correlated k-model for spectral radiation penetration within liquid fuels. International Journal of Heat and Mass Transfer, 158, 119990. https://doi.org/10.1016/j.ijheatmasstransfer.2020.119990
2. Alinejad, F., Bordbar, H., & Hostikka, S. (2021). The ordinate weighting method for solving radiative heat transfer through a Fresnel interface. Journal of Quantitative Spectroscopy and Radiative Transfer, 270, 107685 https://doi.org/10.1016/j.jqsrt.2021.107685
3. Alinejad, F., Bordbar, H., & Hostikka, S. (2021). Improving the modeling of spectral radiation penetration into the condensed materials with the separated full spectrum correlated-k method. International Journal of Heat and Mass Transfer, 176, 121448. https://doi.org/10.1016/j.ijheatmasstransfer.2021.121448
4. Alinejad, F., Bordbar, H., Makowska, M., & Hostikka, S. (2022). Spectroscopic determination of the optical constants and radiative properties of black PMMA for pyrolysis modeling. International Journal of Thermal Sciences, 176, 107501. https://doi.org/10.1016/j.ijthermalsci.2022.107501
5. Alinejad, F., Bordbar, H., & Hostikka, S. (2022). On the importance and modeling of in-depth spectral radiation absorption in the flammability analyses of black PMMA. Fire Safety Journal, 103706. https://doi.org/10.1016/j.firesaf.2022.103706

First two dealt with fundamental methodological development for thermal radiation modelling. The third and fourth were focus on the material modelling using non-gray methods, and the fifth combined all these methods into pyrolysis modelling in fire engineering.

Prof André’s visit was an intersting opportunity for us at Aalto to learn about the forefront of radiation modelling. We look forward in new collaboration in this field.

Posted by Simo Hostikka

Rahul has reach a point at his research path at Aalto University, when it is time to say Goodbye! He started in Aalso’s FSE group as a MSc thesis worker in PAHAHUPA -project. From that project, he received two journal articles:

1. Kallada Janardhan, R., Hostikka, S. Experiments and numerical simulations of pressure effects in apartment fires. Fire Technology, 53(3):1353-1377. 2017. http://doi.org/10.1007/s10694-016-0641-z
2. Hostikka, S., Kallada Janardhan, R., Riaz, U., Sikanen, T. Fire-induced pressure and smoke spreading in mechanically ventilated buildings with air-tight envelopes. Fire Safety Journal, 91:380-388. 2017. doi:10.1016/j.firesaf.2017.04.006

Rahul’s doctoral thesis is titled “Understanding fire spread, its influence on structures and fire intervention tactics through computational methods”. You can find the thesis from https://aaltodoc.aalto.fi/handle/123456789/114663

The thesis is built on the basis of four collaborative research papers. First two developed a computational affordable (coarse mesh) CFD method for modelling fire spread on wood. Third investigated the effect of spreading fire on structural response through CFD-FEA coupling, and the fourth one introduced the aspect of fire intervention by developing a CFD model for large fire brigade water sprays and a means to consider cooling in the CFD-FEA coupling.

1. Kallada Janardhan, R., Hostikka, S. Predictive Computational Fluid Dynamics Simulation of Fire Spread on Wood Cribs. Fire Technology, 55:2245-2268. 2019.  http://doi.org/10.1007/s10694-019-00855-3
2. Kallada Janardhan, R., Hostikka, S. When is the fire spreading and when it travels? – Numerical simulations of compartments with wood crib fire loads. Fire Safety Journal, 126: 103485. 2021. https://doi.org/10.1016/j.firesaf.2021.103485
3. Kallada Janardhan, R., Shakil, S., Lu, W., Hostikka, S., Puttonen, J., Coupled CFD-FE analysis of a long-span truss beam exposed to spreading fires. Engineering Structures, 259, 114150, 2022. https://doi.org/10.1016/j.engstruct.2022.114150
4. Kallada Janardhan, R., Shakil, S., Hassinen, M., Lu, W., Puttonen, J., Hostikka, S. Impact of Firefighting Sprays on the Fire Performance of Structural Steel Members. Fire Technology, 2022. https://doi.org/10.1007/s10694-022-01257-8

Rahul’s defense was organized in June 15th, 2022. Opponent was Prof Wojciech Węgrzyński of Institute Techniki Budowlanej, Poland. The examination lasted for about two hours and covered the entire thesis work. Here is a group photo after the defense, with opponent, candidate, and custos wearing black.

As the last project, while waiting for the reviews of his latest journal, Rahul participated in the measurements of LIESIPALO-project.

Posted by Simo Hostikka

We are part of the Nordic Fire and Safety Network!

The Nordic Fire and Safety Network is a consortium consisting of the Nordic universities and research institutes dealing with risk and fire safety. The network is organized by the Technical University of Denmark in collaboration with RISE (Research Institutes of Sweden), Norwegian University of Science and Technology, Lund University, Aalto University, Luleå University, University of Stavanger, Western Norway University of Applied Sciences and Iceland University as well as VTT Technical Research Centre of Finland Ltd and Danish Institute of Fire and Security Technology.

Main activities:

• Seminars on research and education
• Nordic Fire and Safety Days
• PhD student workshops and summer schools
• Researcher exchange

In fall 2021, Aalto hosted a (online) PhD student workshop on the theme of sustainability of research. Next workshop is planned for August 2022.

Posted by Simo Hostikka

Our publicly funded project on the multiphysics simulation of stone-wool fire resistance is now ending. In this project, we studied the thermal behaviour of stone wool and developed simulation models to extend the standard test results. The project was made in collaboration with Owens Corning Paroc who provided experimental test data from 30 different stone wool samples.

The work was published in Fire Technology.

The work was funded by Palosuojelurahasto.

The main conclusions were

• Stone wool, as other non-combustible, A1 class insulation materias contain varying amounts of organic materials that react with oxygen during fire, and produce heat that increases wool temperature even tens of degrees.
• Temperature increase is highest in stone wools with high organic content, but the amount of organic content alone does not explain the whole phenomenon. It is necessary to consider the transport of oxygen too.
• The processes can be best simulated with models that include both heat conduciton, mass transfer, and heterogenous reactions.
• Closing the stone wool between non-permeable linings, like steel sheets in sandwich elements, will prevent oxygen diffusion into the wool, and reduce the cold-side temperatures.

Posted by Simo Hostikka

Simo posted at LinkedIn about the calculation of infection risk and aerosol concentrations in closed spaces with ventilation. This was a result of consultation with public transport -related actors in Finland. In the end of the post, there will be links to a GitHub space with matlab-functions.

Posted by Simo Hostikka

The new cone calorimeter of our research group, manufactured by Concept Equipment Ltd. in UK, has been freshly commissioned and is now entering its research use. Cone calorimeter is a widely used tool in fire performance testing of materials. In principle, the sample is ignited and burned below a truncated cone -shaped heater element, imposing a radiant heat flux in order of tens of kilowatts per square meter. The released smoke gases are collected and analyzed to give heat release rate and other data, while also recording the sample mass. In the figures, the burning sample is of black PMMA plastic.

In addition to the standard testing in atmospheric conditions as in the figures, our new cone calorimeter has also a tailor-made capability to materials testing in reduced oxygen concentrations. This is achieved by closing the doors and vents on the sides of the sample chamber, inserting roof panels on its top, and flushing the chamber with a nitrogen flow from below the sample.

Posted by Aleksi Rinta-Paavola

To celebrate the tenured position of Associate professor, Simo gave his Installation talk in the Aalto-level event, January 30, 2019.

[embedyt] https://www.youtube.com/watch?v=RWJZI9bp868[/embedyt]

Posted by Simo Hostikka