Fire risk management and fighting in large polydisperse room networks – MARINER

This project has three components. The first is to evaluate the characteristic times of fire propagation between two compartments depending on the mode of transmission: through the walls, by the hot gases through the openings and ventilation ducts and along cable trays, taking into account the sprinkling of water in surface and/or volume. The approach is both experimental and numerical. The modelling of fire behaviour at the macroscale (that of the room), and its interaction with the sprinkler system, is based largely on models developed by the project partners (zone model : ŒIL, field models : SAFIR and BERGAMOTE). Laboratory experiments are intended to characterize the fire behaviour of wall elements, protected by a water film or not, exposed to incident heat fluxes representative of fire scenarios (cone calorimeter, test benches), and to validate the code REPARE.
The partners put their experience and their metrological means in common to characterize heat transfer through the wall and liquid film properties (thickness, radiative attenuation). Tests in the 54m3 two-compartment fire facility, specifically designed for the present project, will then be used to study the influence of the fuel load, the conditions of ventilation and the sprinkling of water on the characteristic times. The second component concerns the development of the fire network model, which uses the transmission delays as input data and provides the spatio-temporal evolution of the fire through the whole structure. The last part is dedicated to the validation of the concept on the submarine part of the USS SHADWELL (11 compartments), and a virtual massively multi-compartmented mock-up. Statistical studies and sensitivity (factorial designs, polynomial chaos methods) will illustrate the potential of the network model: risk map, hierarchization of model parameters.

At mid-term:
• Last developments and validation of the computational fluid dynamics model SAFIR (developed jointly by IUSTI and DGA Tn) to specific fire scenarios, including multi compartmented structures, under-ventilated combustion, and fire mitigation using polydisperse water sprays ;
• Development and validation of a pyrolysis model for the treatment of the fire source ;
• Validation of the code PROPAGAZ (DGA Tn) intended to simulate fire propagation in the ventilation system ;
• Thickness measurement of a water film falling on a vertical plate;
• Experimental and theoretical study on the attenuation of IR radiation by a water film;
• Experimental determination of drying-out flow rates for incident heat flux representative of fire scenarios and validation of the code REPARE;
• Designing and building of a 54m3 two-compartment enclosure dedicated to navy fire scenarios ;
• First application to the Patrouilleur P400 of the network fire model.

The present project is a preliminary phase of a long-term project, intended to provide designers and managers with a decision making tool allowing them to reduce the vulnerability of buildings and infrastructure and to allocate fire-fighting resources to maximize public and firefighter safety, reduce environmental impacts, and lower fire-fighting costs. This tool should help in developing better strategies to reduce fire consequences.

P. Boulet, J. Gérardin, Z. Acem, G. Parent, A. Collin, Y. Pizzo, B. Porterie. Optical and radiative properties of clear PMMA samples exposed to a radiant heat flux. Int. J. thermal Sci. 82(1) (2014) 1-8.
Y. Pizzo, C. Lallemand, A. Kacem, A. Kaiss, J. Gerardin, Z. Acem, P. Boulet, B. Porterie, Steady and transient pyrolysis of thick clear PMMA slabs. Combust. Flame, in press.
Y. Baara, N. Zekri, L. Zekri, Y. Pizzo, A. Kaiss, J. P. Clerc, B. Porterie and C. Lallemand, Modeling percolation in polydisperse systems, EPL, 102 (2013) 46003.
D. Brissinger – G. Parent – P. Boulet. Experimental and theoretical study on radiation attenuation by a water film. J. Quant. Spec. Rad. Trans.145 (2014) 160-168.
A. Collin, R. Berfroi, Z. Acem, G. Parent, P. Boulet, Y. Billaud, Y. Pizzo, A. Kaiss, B. Porterie. Identification of temperature and species within real flames using IR spectrometry data, Conf. INTERFLAM, London, juin 2013.
G. Parent, R. Morlon, P. Boulet. Visibility through a mixing of water mist and smoke, 11th International Symposium on Fire Safety Science, Univ. of Canterbury, New Zealand , Fév. 2014.
B. Kadoch, A. Kaiss, Y. Pizzo, C. Lallemand, S. Suard, B. Porterie, Etude du comportement d’un feu dans une structure multi-compartimentée et ventilée mécaniquement, JITH 2013, Marrakech.
Y. Pizzo, C. Lallemand, N. Giraud, A. Kaiss, B. Kadoch, B. Porterie, Etude du comportement thermique d’une paroi soumise à un incendie et de sa protection thermique par film d’eau, JITH 2013, Marrakech.
S. Suard, A. Kacem, H. Martin, B. Porterie, Simulations prédictives d’un feu d’hydrocarbure - Etude de l’influence de la viciation de l’air, CFM 2013, Bordeaux.
D. Brissinger et al., Protection d’une paroi par film ruisselant – Évaluation couplée de l’épaisseur de film et de l’atténuation des flux rayonnés, GDR Feux, Niort, Janvier 2014.
Y. Pizzo et al., Etude expérimentale et numérique de la dégradation thermique d’un composite naval, GDR Feux, Niort, Janvier 2014.

Predicting the behavior of fire in confined enclosures with and without mitigation using water-based firefighting systems is a topic of great interest for both civil and military fields. Although notable advances have been made in this area from prescriptive or analytic approaches, these conventional approaches fail in reproducing fire behavior in polydisperse amorphous massively multi-compartmented structures (e.g. naval vessels, high-rise buildings, warehouses, or nuclear plants). The reasons are manifold: the lower relevance of the physical models used the difficulty in accounting for the role of some influential factors on fire behavior, and/or the requirement of prohibitive amounts of memory and computational resources.
The present project aims at modeling and achieving super-real time simulations (faster than real time) of fire propagation and its limitation using water systems in such complex structures. The approach we propose to describe large-scale fire behavior is based on the purely stochastic small-world network model developed by Watts et Strogatz in the end of the nineties to account for both short-range and long-range connections, between adjacent and remote compartments. To finely describe the dynamics of fire, the original network model will be extended by incorporating a weighting procedure on sites, the weights being determined from the characteristic times of heat transfer from compartment to compartment: wall conduction, hot smoke flow through corridors, openings and ventilation pipes, cable trays. This determination will be made from specific lab-scale experiments -by exposing both homogeneous and composite wall panels to incident radiant heat flux representative of fire conditions- and from numerical simulations of fire behavior and its interaction with the water spray using a deterministic macroscopic two-phase model. Complementary experiments will be conducted in a dedicated fire box in order to validate the macroscopic model, but also to collect basic data on the level of thermal stress the structure may undergo.
Concept validation consists of two steps. First, we will use results obtained from experiments conducted in the submarine part of the USS SHADWELL. These experiments involved fire propagation in a few compartments and the operation of a water spray system. Second, the partners will have to define an amorphous polydisperse network composed of a large number of compartments. A sensitivity analysis will be carried out in order to identify and classify the most influential parameters of the fire propagation model, and to study the response of the system to the variations of these parameters. The capability of the model to elaborate fire risk mapping and to evaluate network properties will be demonstrated by means of a statistical study. Network properties include percolation threshold, super-nodes (highly-connected nodes) and critical channels along which the fire will propagate preferentially. Evaluating network properties should help in developing better strategies to reduce fire consequences.
The present project is a preliminary phase of a long-term project, intended to provide designers and managers with a decision making tool allowing them to reduce the vulnerability of buildings and infrastructure and to allocate fire-fighting resources to maximize public and firefighter safety, reduce environmental impacts, and lower fire-fighting costs.