流动/运动松耦合与紧耦合计算方法及稳定性分析

为了更加精确地模拟流动/运动耦合问题, 建立了耦合动态混合网格生成非定常流场计算和六自由度运动方程求解的一体化计算方法, 并在统一框架内同时实现了松耦合与紧耦合方法.通过圆柱涡致自激振荡(vortex induced vibration, VIV)的模拟, 对不同时间精度的松耦合和紧耦合算法的优劣及适用范围进行了评估和分析; 通过引入附加质量的概念, 对耦合算法的稳定性进行了理论分析.研究表明:在流体的密度与物体的密度接近时, 松耦合方法是不稳定的, 必须采用紧耦合方法.最后利用耦合算法对二维鱼体的自主游动和钝锥三自由度自由飞过程进行了数值模拟, 证实了理论分析的结论. 

Loose and Strong Coupling Methods for Flow/Kinematics Coupled Simulations and Stability Analysis

In order to simulate the flow/kinematics coupled problem more accurately, an integrated method which couples the dynamic hybrid grid generation, unsteady flow simulation, and computation of flight mechanics equations was presented. The loose coupling method and the strong coupling method (or fully-implicit method) were achieved in a unified framework. The vortex induced vibration (VIV) of a cylinder was simulated to compare different coupling algorithms and investigate their performance. Furthermore, the stability condition was studied for these coupling algorithms. Finally, the S-type starting with self-propelled swimming of a 2D model fish and a blunted cone 3-dimension free-flight process were simulated with the present coupling algorithms. The numerical and theoretical results validate that the loose coupling methods will result in instability when the added-mass is very close to the real mass of the solid. In that case, the strong coupling method will be a better choice.