低速大雷诺数混合飞艇气动性能分析

针对混合飞艇体积巨大同时气动外形复杂使得现有条件的风洞试验很难精确测量其气动性能的问题,开展了适用于混合飞艇气动性能分析的计算流体力学(CFD)的数值分析方法研究。考虑混合飞艇低速大雷诺数的特点,将变分多尺度方法 (VMS)与动态Smagorinsky大涡模拟(LES)模型相结合,提出了组合的VMSLES湍流模型。将基于RANS方法和LES方法的其他三种湍流模型相对比,利用雷诺数相近、实验数据丰富的6:1长椭球飞艇对不同的湍流模型进行了对比验证。结果显示LES方法预测结果与实验结果吻合较好,优于RANS方法,并能显示更多流动细节,而组合的VMS-LES模型能够更精确地捕获实验研究中观察到的二次涡。利用组合的VMS-LES模型对有翼HAV与多囊瓣HAV进行了气动性能分析,并研究了不同部件对飞艇气动特性的影响。结果表明,由于尾翼表面产生的一次涡与二次涡相互作用,尾翼在增加气动升力的同时也增加了阻力。

Aerodynamic Performance Analysis of Hybrid Air Vehicles with Large Reynolds Mumber

In view of the problem that the large size and complicated aerodynamic appearance of hybrid airships making it difficult to accurately measure their aerodynamic performance in wind tunnel test under existing conditions,a numerical analysis method of computational fluid dynamics(CFD)for aerodynamic performance analysis of hybrid airships is developed.A combination of the variational multiscale method and the dynamic smagorinsky model is investigated and three other different turbulence models of RANS methods and VMS-LES methods are compared for this study.The validation of the turbulence models is carried out for a 6:1 prolate spheroid because of its similarity of Reynolds number and abundant experimental data.Results show that the predictions using LES methods express better agreement with the experiment than the RANS methods and they can display more flow details.The combined LES model can capture a secondary vortex which is effectively observed by experimental studies.Aerodynamic performances of the winged HAV and multi-lobed HAV are carried out using the combined LES model at last.The effects of different components on the aerodynamic properties of the HAV are studied.It can be seen that the tail adds the aerodynamic lift as well as increasing the drag,because of the interaction of first and secondary vortex generated on the fin surface.