悬停旋翼桨尖涡吹气控制的数值模拟

Numerical Simulation of Flow Conrtol on Blade Tip Vortex of Hovering Rotor by Slotted Blowing

开槽桨尖是减弱旋翼桨尖涡强度的一种被动流动控制手段。旋翼桨尖涡由于涡量高度集中在一个很小的区域范围内,数值计算容易受到网格分布和数值耗散的影响,导致涡量耗散过快,不利于对旋翼尾迹涡开展研究。针对这一问题,文中采用重叠网格局部加密和湍流模型旋转修正等方法,获得了悬停旋翼的高分辨率桨尖涡流场。采用该方法,对比研究了Caradonna-Tung旋翼基本外形和开槽桨尖外形在悬停状态下的空间旋涡流场,从涡量分布、旋涡特征速度等方面研究了开槽桨尖控制桨尖涡强度的流动机理,比较了4种不同开槽方式对控制效果的影响,以及对旋翼悬停性能的影响。结果表明,开槽桨尖能够有效减弱桨尖涡的强度,但同时会对旋翼拉力和扭矩产生一定的负面影响。

Slotted blade tip is an newly developed design to reduce the strength of tip vortex. In numerical simulation, vortex strength is likely to suffer from unreasonable mesh distribution and computational method because of its highly concentrated structure, which leads to premature dissipation of vortexs, and makes it hard to track the wake vortex development. To the question, special techniques are adopt- ed in the simulation including local refinement of overlap grids and rotation correction of turbulence model, and high resolution tip vortex flowfields are obtained. Thereafter, the hovering flowfields of Caradonna-Tung rotors equipped with original and slotted tip are numerically simulated, vorticity con- tours and characteristic velocities are discussed to study the flow mechanism, and four slotted blade tips are compared for their control efficiencies and performance losses. Results show that slotted blade tips reduce the strength of the blade tip vortex effectively, and at the same time, some minus effects are in- duced such as thrust loss and torque addition.