有黏流场中旋成椭球体的轴向附加质量系数计算

Abstract

为了估算有黏流情况下飞艇的轴向附加质量系数,采用计算流体动力学（CFD）技术计算了有黏流情况下椭球体在时变来流速度下的气动力随时间变化曲线,然后通过傅里叶分析法辨识得到了椭球体的非定常气动力系数,最后将与加速度相关的气动力系数折算成轴向附加质量系数.通过研究相同空速下,来流速度对气动力的影响,将运动体在静止来流中运动的气动力计算问题转化为相同空速下运动体静止而来流时变的气动力计算问题.这种转化避免了在CFD计算中使用动网格技术.数值计算的结果表明:在一定的条件下,有黏流场中也可以定义轴向附加质量的概念;但有黏流的轴向附加质量和无黏流中的结果有较大的差异.To estimate the axial added mass(AAM)coefficient of the airship in viscous flow,we have computed the aerodynamic force of an ellipsoid suffered in a uniform but unsteady incoming flow based on CFD technology.The Fourier analysis method is then adopted to identify the unsteady aerodynamic force coefficient.At last,the acceleration-related aerodynamic coefficient is converted to AAM coefficient.By studying the effect of the incoming flow velocity on the aerodynamic force under the same airspeed,this computational problem of a solid moving in the fluid that rests at infinity is transformed into the case where the solid is stationary while the velocity of the incoming flow is time-varying.This transformation avoids adopting the dynamic mesh technology in CFD simulation.Numerical results show that,under certain conditions,the concept of AAM can also be defined in the viscous flow field.However,the AAM in viscous flows deviates from the corresponding result in potential flows distinctly.