This study focuses on the analysis of the laminar-turbulent transition of the flowfield in a channel with fluid injection through a porous wall. Such a configuration is representative of the flowfield inside solid rocket motors. The flowfield is obtained thanks to unsteady three-dimensional LES numerical computations. In order to trigger the transition from a laminar state to a turbulent one using LES approach, it turns out to be necessary to introduce some perturbation in the flowfield. This study concentrates on searching a method to generate such perturbations. A first attempt has been made using the properties of the numerical scheme of the CEDRE CFD code of ONERA. A second approach that enables to take into account some experimental data has been developed. The experimental data is provided from the VECLA cold-gas setup of ONERA. This second method is based on the stochastic model from the Langevin equation. This equation has been implemented in the CEDRE code. A numerical study of the behaviour of such a model for the simulation of the transitional state of the flowfield obtained in channel with fluid injection through a porous wall has been done. The three-dimensional unsteady LES simulations of the flowfield in the VECLA setup have then been carried out using the CEDRE code. The results have been compared with the experimental data and with the results from a RANS computation. The benefit of using the stochastic equation of Langevin for the simulation of the turbulent quantities of such a flowfield has been pointed out.
