Multiresolution technique and explicit–implicit scheme for multicomponent flows

In the context of multicomponent flows, we are faced with PDE systems solutions combining waves whose speeds are several orders of magnitude apart. Of these waves, only the slow kinematic ones that represent transport phenomena are of concern to us. The fast acoustic ones, although uninteresting for the physical application considered, nevertheless impose a prohibitively small time-step (via the classical CFL restriction) if treated explicitly. This is why we propose to use a hybrid finite-volume scheme in which fast waves are handled by a linearized implicit formulation and slow waves remain explicitly solved. To further decrease the computational cost, mostly due to the complexity of nonlinear thermodynamical laws, we combine this method with a fully adaptive multiresolution scheme. At each time step, a multiscale analysis followed by the thresholding of small details enables us to discretize the solution over a time-varying adaptive grid, based on the smoothness of the relevant phenomenon. Particular attention is given to the extension of the reference scheme to non uniform grid and to the prediction strategy of the adaptive grid from one time-step to another. Finally, efficiency in terms of computing time requirements is studied in conjunction with the accuracy performances.