面向超声速民机层流机翼设计的转捩预测方法

Automatic transition prediction is crucial for the natural-laminar-flow wing design of supersonic transports. Traditional transition prediction methods for low speed and transonic laminar-flow wing design generally only consider 2D Tollmien-Schlichting (TS) waves and stationary Crossflow (CF) waves, which are not suitable for prediction of flow transition induced by oblique TS or traveling CF waves in supersonic boundary layers. This study develops an e^Ntransition prediction method with an improved amplification factor computation strategy, taking into account three-dimensional oblique TS waves and traveling CF waves. This method adopts the fixed-wave-angle and fixed-frequency methods to search for unstable TS and CF modes and the fixed-transverse-wavenumber-and-fixed-frequency method or the envelope method to compute amplification factors of perturbations. The method is further coupled with a Reynolds-Averaged Navier-Stokes equation (RANS) solver for automatic transition prediction in flow simulation. The proposed method is used to analyze boundary-layer stability of NASA's experiment 65°-swept-wing at Mach number 2.0. The computed amplification factors of traveling and stationary CF waves agree well with the results in the reference work. Furthermore, the proposed method is applied to natural-laminar-flow design of an infinite-span swept wing with a swept angle of 60° at Mach number 2.0. Reynolds number 1.39×10⁷. We propose an ideal pressure distribution which quickly accelerates the flow near the leading edge and then keeps it in a mild pressure gradient. The designed wing is evaluated and nearly full laminar flow is observed over the upper surface, indicating the applicability of our method for aerodynamic design of the natural-laminar-flow wing of supersonic transports.