DECOMPOSITION LINEAR NONLINEAR OF UNSTEADY-FLOW

The unsteady inviscid flow of an incompressible fluid around a moving lifting surface is considered. It is assumed that the unsteadiness can be split in two parts, the first one corresponding to a mean motion and the second one to pertubations which are small enough to be accounted for with a linear theory. The resulting decomposition is used to build up a numerical method. This method is applied to the flow around a square flat plate and is tested by comparing the result obtained with those from a fully non-linear calculation.