椭圆柱绕流摆动流固耦合的数值模拟

为了分析不同影响因素对椭圆柱绕流摆动规律的影响,采用计算流体动力学——刚体动力学耦合模型进行椭圆柱绕固定轴摆动的双向流固耦合数值模拟.通过求解二维非定常不可压缩黏性流体N-S方程和SST k-ω湍流模型控制方程,研究不同长短轴比(0.6, 0.8, 1.0),不同偏心距离比(0, 0.2, 0.4, 0.6, 0.8)和不同雷诺数(3 900, 5 000, 10 000)的椭圆柱绕流的流动特征,分析了不同工况下椭圆柱绕流的运动和流动规律.结果表明,椭圆柱的摆动角度θ随着长短轴比和雷诺数的增大而增大,随着偏心距离比的增大先增大后减小;椭圆柱的摆动频率和雷诺数呈良好的线性递增关系,但长短轴比和偏心距离比对椭圆柱的摆动频率影响不明显.分析了椭圆柱绕流的尾流演变以及瞬时压力系数的变化,揭示了椭圆柱绕流摆动的机理,为利用椭圆柱开发海洋海流能和低水头水能资源提供了依据.

Numerical simulation of fluid-solid rotating motion of rigid elliptic cylinder

Two-way fluid-solid interaction of the fixed-axis auto-rotation of rigid elliptic cylinder was simulated numerically using a coupled computational fluid dynamics(CFD)—rigid body dynamics(RBD)model. By solving two-dimensional unsteady incompressible N-S equations and SST k-ω turbulent governing equations, wake flow features and motion characteristics of elliptic cylinder were investigated in different axis ratios, eccentric distance ratios and Reynolds number conditions. Accor-ding to the simulated results, swing angle θ of the elliptic cylinder increases with axis ratios and Reynolds number increasing. In addition, with the eccentric distance ratios increasing, swing angle θ of the elliptic cylinder first increases and then decreases. A linear growth relationship can be observed between the swing frequency of the elliptic cylinder and Reynolds numbers, while axis ratios and eccentric distance ratios illustrate insignificant influence on the swing frequency of the elliptic cylinder. Wake evolution behind the cylinder and variations of instantaneous pressure coefficients were analyzed in order to reveal the mechanism of swing motion of eccentric elliptic cylinder. The results provided fundamental support for the utilization of ocean current energy.