Effect of Compressibility on the Trapped Vortex in the Gap between the Coaxial Disk and Cylinder and the Drag of Their Arrangement for Axisymmetric Sub-, Trans-, and Supersonic Flow

Abstract: The effect of air compressibility on circulation flow in a large-scale vortex trapped in the gap between the coaxial disk and cylinder is investigated numerically. The sub-, trans-, and supersonic axisymmetric flow and the drag of the disk-cylinder-disk body arrangement close to the optimum in the profile drag for the incompressible medium is considered in the Mach number range from 0 to 3. Grid convergence and adequacy of numerical predictions are justified by their comparison with the available experimental data. The modification of the shock-wave structure from the normal shock appearing above the shear layer and to formation of the λ-shock above the lateral surface of the cylinder observed in the transonic range of the Mach numbers from 0.75 to 0.95 determines the rapid growth of the wave drag of the arrangement. It is shown that in the kernel of trapped vortex the density, the temperature, and the turbulence characteristics vary only slightly above M = 0.8.