Performance of implicit methods in moving boundary problems

The problem of relative motion of two parts of a flying vehicle is of interest in a lot of practical application. Numerical simulation of such problems has been developed during recent decades. Moving grid and numerical algorithm for solution of the governing equations are two main features of the numerical simulation. This paper deals with the numerical algorithms. The governing equations are time dependent and usually, solution of the equations is performed using explicit methods. One of the drawbacks of the explicit methods is that they are limited to small time steps due to the numerical stability problem. Such methods are not efficient for the processes which their time scale is too small in comparison with the numerical time step size. Separation of a booster from a spacecraft is an example of such processes. For these processes, implicit methods may have better performance. In the present work, the performance of the implicit methods is discussed for such processes. To do this, Euler equations are adopted as governing equations and are solved in unstructured moving grids in two dimensional spaces. The equations are solved using full implicit. Finally, for flow solution using full implicit method (Generalized Minimal Residual (GMRES) method with preconditioner) leads to results with acceptable accuracy in a shorter time in comparison with explicit method. (author)