基于合成射流的平尾气流分离抑制机理研究

Unsteady interaction of rotor tip vortex lead to empennage flow separation, and results in empennage unsteady aerodynamic loads increase and abrupt change of helicopter pitching moment. Inspired by the active control technology of airfoil flow separation, empennage surface synthetic jet which is used to suppress the empennage flow separation under interaction of the rotor tip vortex is proposed in the project, and a RANS/Viscous Vortex Particle hybrid method including the vorticity diffusion effect and Poisson equation is established to solve problem, the vorticity diffusion effect in the overlapping region and the pressure variation, in the conventional CFD/vortex hybrid method. The characteristics of airfoil flow with vortex and empennage flow separation induced by rotor tip vortex is then the studied, and the action principles of synthetic jet on the airfoil flow characteristics with vortex and empennage flow separation characteristics under interaction of rotor tip vortex are also researched. Finally, the inhibition mechanism of empennage flow separation with synthetic jet under interaction of rotor tip vortex is revealed. The project focuses on solving the basic rotorcraft aerodynamic problem of the suppression principle of empennage flow separation with synthetic jet under interaction of rotor tip vortex from the aspect of theoretic analysis, and lay a theoretical foundation for active control technology of rotor/empennage unsteady aerodynamic interaction.

旋翼桨尖涡的非定常干扰触发平尾气流分离，并导致平尾非定常气动载荷增加以及直升机俯仰力矩陡变。受翼型气流分离主动控制技术启发，项目提出平尾表面合成射流主动控制方式，抑制旋翼桨尖涡干扰下的平尾气流分离，建立基于涡量扩散效应和Poisson方程的RANS/粘性涡粒子混合方法，解决常规CFD/涡混合方法的重叠域涡量扩散和压力脉动问题，并研究点涡诱导翼型流动特性和桨尖涡诱导平尾气流分离特性，以及射流对点涡干扰下翼型流动特性和旋翼桨尖涡干扰下平尾气流分离特性的作用原理，揭示射流对旋翼桨尖涡干扰下的平尾气流分离抑制机理。项目从理论分析角度重点解决射流对旋翼桨尖涡干扰下平尾气流分离抑制原理这一基本旋翼空气动力学问题，为旋翼/平尾非定常气动干扰主动控制技术奠定理论基础。

旋翼桨尖涡干扰下的平尾非定常流动和气动载荷特性对直升机操纵特性具有较大的影响。本项目完善了旋翼桨尖涡的粘性涡粒子法，嵌入平尾流动模拟的CFD方法，建立基于涡量扩散和压力的耦合模型，构建RANS/粘性涡粒子混合法的旋翼桨尖涡/平尾非定常气动干扰计算方法。通过对旋翼桨尖涡时变特性、物面非定常干扰下的桨尖涡结构和流场变化、旋翼桨尖涡对平尾非定常压力、涡结构、流场、气动载荷的研究，明确了旋翼桨尖涡在平尾非定常气动载荷中的关键作用，并表明了低速状态下由旋翼桨尖涡导致平尾表面气流分离。随后，通过研究射流对平尾气流分离、压力分布、气动载荷的影响特征，获得抑制平尾气流分离的射流控制规律，揭示了射流对平尾气流分离的抑制机理。