考虑地面效应的翼型动态特性数值模拟

为了研究考虑地面干扰的飞行器非定常气动特性,基于滑移网格技术,通过求解二维非定常Euler方程,对不同近地高度下的NACA0012翼型的动态振动特性进行了数值模拟。分析了存在地面干扰时的升力系数以及俯仰力矩系数迟滞环变化,并结合强迫振动法,计算了翼型各个近地高度下的纵向组合动导数。结果表明,地面效应不仅对定常流场产生影响,更显著地影响了非定常气动力及力矩,近地高度越小,这种效应越明显,使得升力系数的迟滞环面积变小,幅值减小,而俯仰力矩系数的迟滞环变化不规律,力矩系数的动导数随着近地高度减小而增大(绝对值减小),纵向的动态稳定性产生损失。地面效应干扰在飞行器非定常气动研究中应该引起重视。

Numerical Simulation on Unsteady Flow Around an Oscillating Airfoil with Ground Effect

To simulate the unsteady flow around an oscillating NACA 0012 airfoil with ground effect , the Euler equations are solved and sliding mesh is used ,then the dynamic characteristics are investigated numerically at different heights between airfoil and ground , and the change of lift and moment hysteresis loops are analyzed ,finally combined with small amplitude oscillation method ,all the dynamic derivatives at different heights are calculated .The result show that ground effect has influence on both steady and unsteady flow fields ,the lift hysteresis loop changes smaller as the height lower ,while the moment dynamic derivative become bigger ,which means making loss on longitudinal dynamic stability .The ground effect should be considered during unsteady aerodynamic research .