高超声速钝双楔绕流流动转捩与分离流动的壁温影响

Wall Temperature Effect on Transition Flow and Separated Flow in Hypersonic Flow Around a Blunt Double Wedge

为研究壁温对吸气式高超声速飞行器进气道转捩流动的影响,选取钝双楔这一典型外形,基于德国Aachen工业大学Thomas与Herbert所开展的双楔高超声速风洞试验,分析了一些已有的计算流体力学(CFD)研究内容,并结合本文不同方法的CFD数值模拟结果,讨论了不同壁面温度对该双楔模型高超声速绕流流动转捩与流动分离的影响。对于双楔模型,流动分离一般发生在拐角附近,由于流动分离旋涡的剪切作用会诱发流动转捩,转捩又会改变流动分离强度、分离涡尺寸,若分离流动存在非定常特征则将导致非定常旋涡运动与流动转捩的复杂相互作用。通过比较已有文献的CFD数值模拟结果与本文计算结果,表明只有按照转捩思路开展的数值模拟才能够反映该风洞试验情况。计算结果与试验数据的比较显示,文献中按照第一压缩面层流与第二压缩面湍流状态计算得到的结果能够在一定程度上与风洞试验数据相符,本文使用MUSCL格式、剪切应力输运(SST)湍流模型与γ-Reθ关联转捩模型这种计算方法,得到的结果与试验数据符合较好,正确地反映了风洞试验情况。分析还表明,在分离流动之前的区域,随着壁面温度的升高,壁面热流会下降,近壁区域黏性系数变大,边界层内速度剖面不饱满,速度边界层较厚,厚的速度边界层容易发生流动分离现象。

To study the effect of different wall temperatures on the engine inlet transition flow for an air breathing hypersonic vehicle,a typical model of blunt double wedge is chosen in this paper.Based on the tunnel experiments carried by Thomas and Herbert from Aachen University in Germany,some existing computational fluid dynamics （CFD） results are analyzed and compared with the numerical simulation results obtained by different methods in the paper.So the effect of different wall temperatures on the transition flow and separated flow in hypersonic flow around a double wedge is discussed.About the flow around the double wedge the separated flow generally occurs around the corner,and the stress of the separated vortex induces the transition,so the intensity and the size of separated flow change,finally the complicated interaction of non-stationary vortex movement and flow transition occurs.The calculation results show that the numerical simulations carried out considering transition simulation accord with the tunnel experiments.Also the comparing results between the calculation and the experiments show that in the literature,the results obtained by using laminar flow solver on the first ramp and turbulent flow solver on the second ramp are consistent with the experimental data,and in the paper the results obtained from the simulation only using the combined method of MUSCL,shear stress transport （SST） model and γ-Reθ model accord with the experimental data and reproduce rightly the status of the tunnel experiment.The analysis shows that in the region before the separated flow the wall heat flux decreases and the viscosity coefficient near wall increases with the wall temperature increasing; in the boundary layer the velocity profile is not in full and the velocity boundary layer is thicker,so the separated flow occurs even easier.