对转螺旋桨流场气动干扰数值模拟

基于结构网格动态面搭接技术，通过求解三维非定常雷诺平均纳维-斯托克斯(RANS)方程，对单独螺旋桨(SRP)滑流流场进行了数值模拟，结果与风洞试验数据吻合良好，在此基础上深入研究了对转螺旋桨（CRP）的非定常滑流效应及前后桨之间的气动干扰现象。计算结果表明:所采用的非定常RANS方法能够良好刻画对转螺旋桨滑流流场的发展变化特征，适用于分析前后桨气动干扰特性。前后桨桨尖涡的复杂相互作用是导致对转螺旋桨气动干扰的直接原因，后桨桨尖涡对于前桨桨尖涡具有一定耗散作用。在气动干扰影响下，对转螺旋桨气动力会产生周期性波动，波动周期与螺旋桨桨叶数相关, 6×6对转螺旋桨在1个旋转周期内产生了12次波动。气流穿过对转螺旋桨会发生两次加速，因此在相同工况下，对转螺旋桨的拉力系数和功率系数相比于单独螺旋桨分别增大约1倍，效率提升约1.5%。 

Numerical simulation of contra-rotating propeller flowfield aerodynamic interactions

On the basis of dynamic patched grid technology, numerical simulations were implemented on an isolated single-rotating propeller (SRP) configuration by means of solving three-dimensional unsteady Reynolds averaged Navier-Stokes (RANS) equations, and the numerical results were verified by wind tunnel test, showing good agreements with the experimental data. Subsequently, emphasis was placed on investigation of the unsteady flowfield characteristics and aerodynamic interactions of contra-rotating propellers (CRP) configuration. The results showed that the unsteady RANS approach allow for a detailed analysis of the developing characters of the slipstream flowfield and aerodynamic interactions between the two propellers. The main reason of the aerodynamic interactions lied in the mutual effects of the blade tip vortices generated by the front and aft propellers, and the aft propeller reduced the strength of the blade tip vortices of the front propeller. Aerodynamic interactions could lead to the periodic oscillations of the aerodynamic forces, and the frequency of the oscillations was linked to the blade numbers. The 6×6 CRP configuration had 12 aerodynamic oscillations in one full rotation. The freestream could be accelerated twice when passing through the CRP, therefore compared with SRP, the thrust coefficient and power coefficient of CRP almost would be doubled in the same working conditions, meanwhile the efficiency would increase by approximately 1.5%.