CFD modeling of hydrogen deflagration in a tunnel

In this paper CFD modeling techniques are used to simulate deflagration in homogenous, near stoichiometric hydrogen-air mixture in a model of a tunnel. The tunnel is 78.5 m long. Hydrogen-air mixture is located in a 10 m long region in the middle of the tunnel. Two cases are studied: one with a complete empty tunnel and one with the presence of four vehicles near the center of the tunnel. The combustion model is based on the turbulent flame speed concept. The turbulent flame speed is a modification of Yakhot's equation, in order to account for additional physical mechanisms. A sensitivity analysis for the ψ parameter of the combustion model and for the mesh resolution was made. The agreement between experimental and computational results concerning the value of the maximum pressure, and the time it appears, was satisfactory in both empty and non-empty tunnel case. The sensitivity analysis for the parameter of the combustion model showed that even small changes in it can have impact on the simulating results, whereas the sensitivity analysis of the mesh resolution did not reveal any significant differences. Finally, the effect of the turbulence model is examined (LES and RANS type of model). The only significant difference in the results between LES and RANS model was the arrival time of the pressure peak. A delay in the arrival time in the case of the RANS model was observed.