Improved k-ω-γ model for crossflow-induced transition prediction in hypersonic flow

Accurate prediction of boundary layer transition is extremely important for the aerodynamic and aerothermodynamic design of a hypersonic vehicle. Crossflow instability plays a crucial role in inducing transition in three-dimensional (3D) boundary layer. In this paper, a crossflow timescale τcross based on crossflow velocity and crossflow Reynolds number is proposed and incorporated into the k-ω-γ transition model. Additionally, a grid pretreating method that can calculate boundary layer parameters with massive parallel execution is also proposed. HIFiRE-5, circular cone at angle of attack and X-33 vehicle are considered as test cases to assess the performance of the improved k-ω-γ transition model. Simulation results demonstrate that the boundary layer edge of complex hypersonic 3D flow can be obtained accurately with the help of grid pretreating method. It has been shown that if crossflow is taken into consideration, the shapes and locations of the transition onsets predicted by the improved k-ω-γ transition model are more consistent with experimental and direct numerical simulation results compared to the original transition model. This indicates that the improved k-ω-γ transition model provides significant improvement when crossflow-induced transition in hypersonic 3D boundary layer flow is predicted. Furthermore, application of the improved k-ω-γ transition model to X-33 vehicle flow shows that this model can be successfully used to predict crossflow-induced transition on complex full aircraft hypersonic configuration.