Experimental and theoretical investigations of the near-wall region in a turbulent separated and reattached flow

A nominally two-dimensional turbulent flow at high Reynolds numbers with a closed separation region is studied in which separation occurs on a flat wall due to the pressure distribution and not because of geometry, e.g., sharp edges. A new experimental setup that is capable of generating the specified flow is described. Three-dimensional LDA measurements of the flow field are complemented by measurements on the surface such as wall pressure distribution and skin friction measurements, the latter by sublayer fences. With these measurements, the constants of the generalized wall function can be deduced. Problems that occurred in generating a nominally two-dimensional flow and arrangements made to avoid these problems are described. A new method is presented to calculate the turbulent velocity field using the high Reynolds number asymptotic theory. An inverse boundary layer method is employed in connection with the method of wall functions. The changing structure of the wall function, when approaching separation, is accounted for. The experimentally determined values of the constants of the wall function are used. Turbulent shear stress is modeled with an asymptotically correct one-equation model. Calculations compare favorably with measurements.