Study on hypersonic forebody transition characteristics based on the amplification factor transport model

The bump-compression forebody constitutes a critical aerodynamic component for hypersonic air-breathing vehicles. Its transition characteristics directly influence the quality of the flowfield entering the engine, thereby impacting the overall efficiency and operational stability of the propulsion system. However, there is currently a lack of systematic investigation into the transition characteristics of bump-compression forebodies, both domestically and internationally, which hampers the provision of an effective basis for related aerodynamic design. This study presents an investigation of the transition characteristics of a hypersonic bump-compression forebody using the National Numerical Wind Tunnel (NNW) software PHengLEIand the Amplification Factor Transport (AFT) model. First, the transition model was validated using the HIFiRE-5 and HyTRV configurations. On this basis, the effects of Reynolds number, angle of attack, sideslip angle, and Mach number on the transition front and aerodynamic characteristics were systematically analyzed. The results demonstrate that Reynolds number and Mach number exert the most significant influence on transition: the transition front moves forward with increasing Reynolds number and rearward with increasing Mach number. As the angle of attack increases, the transition front on the windward surface evolves from a mountain-shaped pattern to a concave-shaped configuration. An increase in the sideslip angle leads to a distinctly asymmetric distribution of the transition front. Compared to laminar flow predictions, accounting for boundary layer transition results in maximum increases of 11.7%, 13.6%, and 10.7% in the lift, drag, and pitching moment coefficients, respectively, while the lift-to-drag ratio exhibits a maximum decrease of 10.1%. This research verifies the reliability of the two-equation AFT model for transition prediction on complex three-dimensional forebodies, providing an effective numerical tool and data support for the aerodynamic design and thermal protection optimization of hypersonic forebodies.