脊形前体俯仰动态绕流数值模拟研究

Simulation of the aerodynamics of a chined forebody oscillating in pitch

针对飞行器俯仰运动时流场结构会跨越显著差异的流态,且其气动力和力矩会呈现强烈的非定常、非线性的动态流场特性,采用IDDES混合湍流模型,研究了脊形角90°的前体俯仰运动时的动态流场特性以及来流马赫数对俯仰振荡动态涡流场结构和非定常气动力的影响。研究结果表明:对于脊形前体大振幅俯仰振荡运动,上仰时前体涡破裂延迟,导致大攻角时升力、阻力和俯仰力矩明显大于相应攻角的静态值;下俯时前体涡再附延迟,且远离机身壁面,导致升力、阻力和俯仰力矩比上仰时小,非定常气动力迟滞效应显著;同时,马赫数越小,俯仰振荡的迟滞效应越显著。

The flow field around an aircraft in pitching motion will span significantly different flow regimes,and the aerodynamic forces and moments show strong unsteady,nonlinear characteristics.The IDDES turbulence model was used to study the effects of an oscillatory pitching motion on the flow field of a chined forebody with 90°chine angle,as well as the effects of Mach number on the dynamic vortex flow structure and the unsteady aerodynamic characteristics.The results show that for large amplitude of pitching motion,in pitching up the breakup of forebody vortices is delayed,so the lift,drag and the pitching moment are obviously larger than the static values at corresponding angle of attack,and in pitching down the reattachment of forebody vortices are delayed and the vortices are far away from fuselage wall,resulting in smaller lift,drag and pitching moment,therefore the aerodynamic forces show significant hysteresis effect.Additionally,Mach number has significant effects on the aerodynamics of chine forebody in oscillatory pitching motion,and the smaller the Mach number,the more significant the hysteresis effect.