Numerical investigations on boundary conditions with turbulence injection and their impact on a high-speed low pressure turbine cascade

This master’s thesis investigates the impact of the inlet boundary conditions on the spatial evolution of the turbulence injected using a library-based method. The free-stream turbulence inflow data has been generated with a precursor approach through the Direct Numerical Simulation (DNS) of a Decaying Homogeneous Isotropic Turbulence (DHIT). Numerical studies have been carried out using the solver ArgoDG, developed at Cenaero, which is based on a high-order discontinuous Galerkin method. Firstly, a parametric study was conducted in a free domain to assess the influence of various simulation parameters (i.e. Reynolds number, Mach number, injection angle, type of boundary conditions and mesh) on the properties of a freely decaying turbulence. The results show that imposing total conditions at the inlet leads the injected turbulence to become anisotropic. Moreover, a non-zero injection angle amplifies the discrepancy between the turbulent kinetic energy associated with the three spatial directions. On the other hand, static inlet conditions result in isotropic injected turbulence, even though the mesh is anisotropic and the injection angle is not zero. Subsequently, static boundary conditions at the inlet were applied to simulate a high-speed low-pressure turbine cascade with high free-stream turbulence. The results were compared with a simulation of the same case but using total inlet conditions. A detailed evaluation of the impact on the flow physics will be presented, including blade loading, boundary layer stability and wake behavior. Overall, the turbulence upstream of the blade exhibits characteristics consistent with those observed in the free domain. Furthermore, the simulation with static inlet conditions shows better agreement with experimental data.