Analytical Approximation Of Two Dimensional Separated Turbulent Boundary Layer Velocity Profiles PDF Download

The bistable, steady, turbulent separation phenomenon observed in a two-dimensional fully-stalled diffuser is studied. Detailed mean flow data including pressure, dissipation and velocity (both magnitude and direction) inside the flow field as well as development of boundary layers on both side walls are reported for cases with thin and thick boundary layers at inlet and with and without fairing curves at the throat. For all cases, most important changes in flow data occur in a region within two inlet widths up and downstream of the throat. Pressure gradients in this region are so large that the boundary layer on the unstalled side changes shape abruptly while the layer on the stalled side separates in the vicinity of the throat. Streamline patterns are obtained from the velocity distributions. The location of the dividing streamline is different for the different cases. Based on the dividing streamline, a displacement line is defined to extend the concept of displacement thickness to the free shear layer which is developed from the separated boundary layer. This displacement line together with the loci of boundary layer displacement thicknesses on the solid walls form an effective channel. The shape and area ratio of this effective channel explain the different trends of pressure distributions in the main flow. (Author).