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Fire simulation

Collage-INURI 1276x978Even small fires produce a large amount of lethal smoke. Therefore smoke spreading in buildings can lead to dangerous situations very quickly. In fact, the majority of fire victims dies by suffocation.

It's not the fire which kills - it's the smoke!

For this reason smoke control is an important issue during the conception (planning) of buildings or other infrastructure. This is especially the case when they are used by a large number of people, like airports, railway stations, shopping malls, theatres or schools.

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Over the last years a paradigm shift has occurred in fire safety engineering. In the past, the risk assessment for fire safety in buildings was based on the provisions of state law for civil engineering. The technical rules are the result of the cognitions of the disastrous con­sequences for life and limb of real fires. One major disadvantage of these rules is their in­flexibly, because common valid standard safety solutions may not be suitable for new modern ar­chitecture and economically efficient solutions.
Therefore new and more flexible tools for risk measurement and assessment for fire safety engineers are desirable. Because of some important changes in the provisions of state law for civil engineering in the European Union, large variations from these standard rules are now permitted. For this purpose a risk assessment must ensure that the same safety level can be reached with alternative solutions.

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With the increasing availability of computational power, computational fluid dynamics (CFD) is steadily becoming more attractive as a risk measurement tool for fire engineers. They employ CFD-programmes as a prediction tool especially for thermal stresses, smoke movement or the usefullness of fire-extinguishing systems or smoke funnels. The solu­tions based on the results of these CFD simulations permit a modern fascinating architec­ture and economically efficient solutions.

Although this is a positive technical development it includes some critical problems. Besides the experience in civil and fire safety engineering additional knowledge in scientific computing is necessary to use CFD-programmes and interpret the com­puted results. This concerns the incorporated physics, the model simplifications and the numerical schemes employed in a CFD-programme. The understanding of this interaction is just as important for trustworthy results as knowledge in fire safety. Nevertheless in-depth CFD knowledge is not a part of the education of most engin­eers, architects, and consultants handling CFD-programmes for fire safety prob­lems. Programmes to compute smoke movement are meanwhile available for all inter­ested users. In the case of the CFD-programme Fire Dynamic Simulator (FDS) even for free. Moreover, advertising suggests easy use of such tools, simple user interfaces, and a large benefit for engineers, architects, and consultants. In this context the conditions to be satisfied in order to obtain reliable results from CFD models are rarely discussed.

In fact, using CFD simulations in fire safety engineering requires a new interdisciplinary combination of different knowledge areas: preventive fire protection, fire defence and additionally scientific computing and numerics for fluid dynamics and combustion prob­lems.Disziplinen3 en As before, a fundamental insight into fire safety regulations and fire safety related details is necessary. Henceforward abstract numerical computations that are actually relevant for problems of fire safety must be created. For example, it is ne­cessary to capture and simulate worst case scenarios (which hopefully will be avoided). Setting up appropriate computations requires considerable experience. Similarly, proper interpretation of the computed data and their translation into technical guidelines for fire-safety demands solid expertise both in the modelling and in the fire safety engineering world. Furthermore we have to take into consideration that new solutions can affect the fire defence. The power of fire brigades is limited, therefore a failure in the fire safety concept could possibly never be compensated. Most likely with disastrous consequences for life and limb.