Application of improved k-ω-γ model to deformed hypersonic Inflatable Aerodynamic Decelerator aeroshell

Abstract

The scalloping surface of Hypersonic Inflatable Aerodynamic Decelerator (HIAD) promotes flow transition. Precise prediction of flow transition and surface aeroheating over the HIAD is imperative to the design of thermal protection system. In this paper, the improved k-ω-γ model considering the separation instability is first applied to the deformed HIAD aeroshell under various angles of attack to assess and verify its performance on such complex configuration, where multiple transition mechanisms coexist and interact. The results of the original k-ω-γ model are also provided for comparison and the prediction mechanisms of the improved model are further dissected. The results reveal that the flow separation and crossflow caused by the scalloping surface are highly sensitive to the angle of attack (α). With the α increasing, an opposite tendency between them can be found, that is, larger α causes stronger and earlier crossflow, but much later flow separation, which leads to the alternation of dominant instabilities for transition in turn. At the relatively high angle of attack, the crossflow becomes critical, at a small angle of attack, however, the separation instability is dominant. The first-mode disturbance can also accelerate the flow instability, while the influence of second-mode disturbance can be neglected due to relatively low post-shock Mach numbers. As a result, the original k-ω-γ model, not attempting to incorporate separated flow transition, predicts an opposite tendency to the experiments. While the transition onset, extent and shape simulated by the improved k-ω-γ model compare quite well with the experiments.