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.