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基于运动嵌套网格方法,建立了一套适合于悬停状态下共轴刚性双旋翼非定常干扰流场分析的计算流体力学(CFD)方法。首先,基于高效的运动嵌套网格技术,采用积分形式的可压雷诺平均Navier-Stokes(RANS)方程作为双旋翼非定常流场求解控制方程,湍流模型选用Baldwin-Lomax模型,时间推进采用双时间方法。在CFD方法的验证基础之上,对干扰过程中的桨尖涡涡核位置及强度演变规律进行了细致分析,揭示了共轴双旋翼非定常干扰流场中上、下旋翼桨尖涡与双旋翼桨叶之间的贴近干扰、碰撞现象,以及上、下旋翼桨尖涡之间的相互干扰机理。然后,进一步研究了不同总距角下的共轴旋翼系统中上、下旋翼的非定常气动特性以及影响规律。计算结果表明:上旋翼桨叶的桨尖涡会直接与下旋翼桨叶发生碰撞,导致下旋翼桨叶拉力损失;上旋翼桨叶的桨尖涡和下旋翼桨叶的桨尖涡相互干扰,改变了桨尖涡的强度和轨迹;上、下旋翼桨叶相互靠近时,上、下旋翼桨叶的拉力均会上升,之后相互远离时上、下旋翼桨叶拉力均会先下降再上升。
A computational fluid dynamics (CFD) method based on the kinematic nested grid method is proposed for the flow field analysis of unsteady coherent double helix rotor under hovering conditions. First of all, based on the efficient nested grid technique, integral Navier-Stokes (RANS) equation is used to solve the unsteady flow field of the twin rotor. Baldwin-Lomax model is used for the turbulence model, Time method. Based on the verification of CFD method, the evolution law of the position and intensity of the blade tip vortex nucleus in the perturbation process is analyzed in detail. It is revealed that the tip vortex and double Close interference between the rotor blades, collision phenomena, and the mutual interference mechanism between the tip vortex of the upper and lower rotor blades. Then, the unsteady aerodynamic characteristics and influence laws of the upper and lower rotor in the coaxial rotor system with different total distance are further studied. The calculation results show that the tip vortex of the upper rotor blade collides directly with the lower rotor blade, resulting in the loss of tension of the lower rotor blade. The tip vortex of the upper rotor blade and the tip vortex of the lower rotor blade interfere with each other, When the upper and lower rotor blades are close to each other, the pulling force of the upper and lower rotor blades will increase, and then the pulling force of the upper and lower rotor blades will first decrease and then rise when the upper and lower rotor blades move away from each other.