Simulation of the Steckler room fire experiment by using SOFIE CFD-model

The recently developed computer fluid dynamics based fire simulation model SOFIE (Simulation of fires in enclosures, version 1.2.3) was applied to predict conditions in case of a well known Steckler et al room fire experiment. The Magnussen combustion model and k-epsilon -turbulence model with buoyancy were adopted for simulations. Flow velocities and temperatures at the doorway centreline of the fire room and temperatures in the fire room have been compared to the experimental results and simulation results of the same problem carried out by using another CFD-model PHOENICS. The results seem to match experimental results and PHOENICS-simulation results quite well. Typically SOFIE predicts temperatures inside the fire room a bit higher than experimental data, but that might be reduced by incorporating the radiation model. All solutions converged when calculation grid was extended horizontally far enough from the doorway. It was necessary first to replace part of the static pressure boundary outside the fire room by virtual walls in order to get solution converge. Then the walls were replaced by the pressure boundaries. We used the three grid types of 26 x 24 x 29 cells. The first one was steady grid, but in the second one there were three regions in each coordinate directions in order to increase grid density at the region of dynamics and interest and get dimensions exact. The third grid type was equal to the second one but divided to half of the original size on the basis of symmetry. When those two latter complex meshes were used, there appeared a strong cross-flow on the bottom of the calculation area outside of the fire room that distorted results and caused unsymmetry. The radiation model proved not to be applicaple with combustion model at the present code version. SOFIE code is still under development and improvement. The next version will be released in near future.