Numerical Simulations Of Rigid Body System's Dynamic Separation And Tethered Control In Supersonic Flows

Moving boundaries exist in a lot of fluid dynamics problems. The study of such problems has very important theoretical and practical value. The dynamic separation behavior of rigid body system in supersonic flow not only involves moving boundaries but also involves shock waves, turbulence, etc.. which makes it is a challenging problem. In this paper, the dynamic separation behavior of free rigid body system and tethered rigid body system in supersonic flow is conducted under the background of orbit prediction and control for large and complex spacecraft during their reentry process.To solve this, a 6-DOF solver is developed first which using quaternion to describe rigid body'orientation and using fourth order Runge-Kutta method to solve the rotational governing equations. This solver can deal with complex geometry by manipulates rigid bodie's surfaces grid. Then, the 6-DOF solver is coupled with VTF's fluid solver[10] using loose-coupling al-gorithm. The fluid solver send boundaries pressure to 6-DOF solver and The 6-DOF solver send boundaries position and velocity to fluid solver. Using level-set method and ghost-fluid method, immersed boundary conditions are enforced. Finally, a parallel software package for fluid structure interaction problems involving complex three dimension rigid body undergoing large displacements is established. The reliability of the solver is verified with a series of nu-merical experiments.The dynamic separate behavior of free rigid body system with different configurations in a supersonic flow (M=4) is simulated. The influence of mass ratio, initial spacing and rotary on the transverse velocity of rigid body is investigated. It is found that the body's transverse velocity is maximum when the body fly along the shock front. At a critical mass ratio for a given initial spacing or at a critical initial spacing for a given critical mass ratio, the body fly along the shock front. The rotary can increase the transverse velocity. During the reentry process, to minimal the bodies'spread range, it is better to chose symmetrical components.The dynamic separate behavior of tethered rigid body system with different configurations in a supersonic flow (M=4) is simulated. The influence of mass ratio and tether length on the stream-wise velocity of system and the bigger body is investigated. By qualitative and parame-terized analyses, it is found that the tether can minimize the spread range of bodies and change the stream-wise velocity of the system. The mass ratio determine the stream-sise velocity of the system. For the system with identical bodies, the tether can decrease the aerodynamic forces on the system. In contrast, for the system different bodies, the tether can increase the aerodynamic forces on the system.