ANALYSIS OF OBJECTS IN FIRE SITUATION WITH THE PFEM J. Marti, S. R. Idelsohn and E. O˜ nate * International Center for Numerical Methods in Engineering (CIMNE) Universidad Polit´ ecnica de Catalu˜ na Campus Norte UPC, 08034 Barcelona, Spain e-mail: julio.marti@cimne.upc.edu, web page: http://www.cimne.com/ 1 INTRODUCTION Versatility features of the polymeric materials such as, high strength, low weight, ease processing, capability to form in complex shapes, etc. have led to their widrespread industrial applications in aircraft structure, transportation vehicles, building and high- way construction, maintenance and finishing products, electronic boards, bioengineering, structural materials, and many other different applications. Their behavior in fire is therefore of considerable interest because they play an important role in the ignition and growth stages of fire. In this paper, a new computational procedure for analysis of the combustion, melting and flame spread of polymers under fire conditions is presented. We follow the way of posing the fluid as well as the solid problem in a Lagrangian frame- work [2]. This approach allows to treat the whole domain, containing both fluid and solid subdomains which interact with each other, as a single entity and describes its be- haviour by a single set of momentum, continuity and energy equations. The equations are discretized with the Particle Finite Element Method (PFEM) [3]. The PFEM, treats the mesh nodes in the fluid and solid domains as particles which can freely move and even separate from the main fluid domain representing, for instance, the effect of water drops. A finite element mesh connects the nodes defining the discretized domain where the governing equations are solved in the standar FEM fashion. 2 GOVERNING EQUATIONS Let Ω ⊂ d , d ∈{2, 3}, be a bounded domain containing two different fluids (see Figure 1). We denote time by t, the Cartesian spatial coordinates by x = x i d i=1 , and the vectorial operator of spatial derivatives by = {∂ x i } d i=1 . The evolution of the velocity u = u(x, t), the pressure p = p(x, t), the temperature T = T (x, t) and the species Y k = Y k (x, t) is governed by equations: dρ dt + ρ∇· u =0 in Ω × (0,T ) (1) 1