Longitudinal vortices in separated turbulent flows

Abstract

The goal of the investigations is the study of the longitudinal vortex formation in high-speed turbulent separated flows caused by relatively small irregularities at the model leading edges or at the model surfaces. Experiments were conducted at Mach numbers 3 and 5 in the Ludwieg Tube Facility at DLR in Göttingen (RWG) with a model of a 2-D compression corner with deflection angles of 20°, 25° and 30°. The irregularities of the surface contour have been artificially simulated by very thin vortex generator strips of different shapes and thicknesses, which were located on the model surface. The dependence of the size and intensity of the observed longitudinal vortices on the introduced disturbances (thickness, shape and wavelength of the vortex generator strips) and on the flow parameters (Mach and Reynolds numbers, boundary layer thickness, compression corner angles etc.) has been shown experimentally. The possible nature of these “long-living” quasi-stationary longitudinal structures in turbulent flows is discussed.