基于微型叶片式涡流发生器的前体压缩面低能流掺混机理

Mixing of low-momentum fluids over the forebody ramp based on micro-vane vortex generators

为了改善高超声速飞行器前体压缩面边界层速度型的饱满程度,降低进气道壁面流动分离的潜在风险,提出了基于阵列微型叶片式涡流发生器的前体压缩面低能流掺混方法。采用数值模拟方法研究了涡流发生器在来流马赫数7状态下的流动特性,揭示了主要流动控制机理,并分析了安装角对掺混效果的影响规律。研究结果表明:微型叶片式涡流发生器可对近壁气流产生一定扰动,形成局部大侧滑角、低压区域,掺混的主要机理在于叶片两侧分别形成扫掠激波、膨胀波,诱导近壁流体向叶片方向偏转,形成局部横向迁移,进而与主流产生掺混效应;负安装角的涡流发生器的扰动能力最强,但总压损失也最大;正安装角时涡流发生器的扰动能力随安装角的增大而增大;相比于无控制状态,所有叶片式涡流发生器均可降低边界层形状因子,安装角15°时的边界层形状因子最小,边界层速度型最为饱满,说明该状态下壁面流动具有较优的抗逆压分离能力。

A flow control method using multiple micro-vane vortex generators is proposed to improve the fullness of boundary layer profiles over the forebody ramp of hypersonic vehicles and to reduce the potential risk of flow separation in the inlet.The flowfield characteristics and mixing mechanism at an incoming Mach number of 7.0 are numerically analyzed.The effect of the installation angle of vortex generators on the flowfield is studied as well.Results show that micro-vane vortex generators can generate a local large-sideslip-angle and low-pressure flow in the near-wall region.At the lateral sides of mocro vanes,glancing shocks and expansion waves are generated,which induce the lateral mixing of low-momentum fluid with the mainstream.When installation angles are positive,with the increase of installation angle,the mixing effect gets stronger but the pressure loss increases.Micro vanes with negative installation angles lead to the strongest mixing effect,however,they also bring significant total pressure loss.Compared with the one without flow control,the shape factor of the boundary layer gets smaller by using vortex generators,among which those with an installation angle of 15 degrees lead to the smallest shape factor and consequently the fullest boundary layer profile,which has better anti-separation capability under reverse pressure gradients.