ИСТИНА

The report presents the numerical investigations of the Mach number effect on the flow around bluff (a circular cylinder) and streamlined (NACA0012 airfoil) bodies. The numerical simulations are based on solving two-dimensional Navier-Stokes equations for viscous perfect gas at small and moderate Reynolds numbers Re (Re≤ 10000) and Mach number range of 0.1≤M≤1.5. The previous experimental and numerical studies have shown that the change of Mach number at a fixed Reynolds number has a significant impact on the near wake flow structure. For example, the flow around airfoil NACA0012 at zero incidence at Re=10000 has regimes with a vortex street in the near wake (0.3<M<0.95) and without it (M<0.3 and M≥0.95), and the transonic regime of 0.7<M<0.85 forms an additional mode of instability1. The work focuses on studying the development of self-oscillations in the subsonic and transonic wakes and related phenomena like unsteady shock/boundary layer and shock/vortex interactions. Fig. 1 shows different types of vortex street formation obtained in the present work: vortex street originates on the body (b) and in the wake in subsonic and transonic flow regimes (a, c). Detailed numerical study of the influence of Mach number on the nature of the flow and forces has been carried out. Initial-boundary value problems for the Navier-Stokes equations are numerically solved by the stabilized finite elements method2. Solutions are built on unstructured meshes using the procedure of adaptation, which automatically creates a good resolution of the grid in the places of local features, such as shock wave, boundary layer and vortex wake. The reported computations have been carried out on Lomonosov supercomputer. The work is supported by RFBR grants (12-01-00405 and 14-01-31106).