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发展了一种用于分析地面效应中瞬态飞行状态旋翼流场的理论模型,采用CB3D时间步进自由尾迹格式求解旋翼的尾迹结构,并采用面元法模拟地面对旋翼流场的影响,针对离散数值计算中出现的部分尾迹涡线落入地面下方的非物理现象,引入了“等体积”修正方法对地面下方尾迹节点的位置进行修正。新模型计算结果显示,计算所得到的地面效应中“环流”和“地面涡”等特殊流动现象的位置和涡强与试验图像符合良好,可以反映瞬态飞行旋翼地面效应中的旋翼气动力变化机理。
A theoretical model for analyzing transient rotor flow field in ground effect is developed. The wake structure of the rotor is solved by CB3D time stepping free wake scheme, and the effect of the ground on the rotor flow field is simulated by the surface element method. Aiming at the non-physical phenomenon that part of the wake vortex line falls below the ground in discrete numerical calculation, the “equal volume” correction method is introduced to correct the position of the wake node under the ground. The results of the new model show that the locations and vortices of the special flow phenomena such as “circulation ” and “ground vortex ” in the calculated ground effect are in good agreement with the experimental images and can reflect the ground effect of the transient flying rotor Rotor aerodynamic change mechanism.