Variational multiscale LES investigation on the influence of boundary layer thickness on the base drag and on the near wake flow of an axisymmetric blunt-based body

This work is a part of an experimental and numerical research activity aimed at characterizing and reducing the base drag of an axisymmetric blunt body. It was observed that the increase of the boundary layer thickness produces a reduction of the base suctions and that this is probably connected with an increase of the length of the mean recirculation region present behind the body, and with the corresponding reduction of the convex curvature of the streamlines outside the boundary layer in the separation region. The results of Variational MultiScale Large Eddy Simulations (VMS-LES) carried out on the same body as in the experiments are presented and analysed. The simulation have been carried out by using AERO. In the numerical simulation the variation of the boundary layer thickness is obtained by using a free-slip boundary condition over different initial portions of the body surface. Of these three simulations we have chosen a base configuration of which we have performed the analysis of the mean flow and the instantaneous flow. Known the nature and dynamics of flow around the body under consideration we then compared the main results of the three simulations performed by highlighting the differences of the terms that play an important role in the drag of the base of the body