Drag Reduction and Diffusion Accompanying Thin Slit Injections of a Drag Reducing Polymer on a Flat Plate at High Reynolds Numbers

摘要

The drag reduction and diffusion accompanying a thin tangential jet injection of an aqueous solution of drag reducing polymer, Polyox WSR 301, into the water turbulent boundary layer of a flat plate at a high free stream Reynolds number, 3.6 x 10 to the 7th power, was investigated for a variety of injected concentrations and ratios of injection to free stream velocities. The wall concentration distribution was found to be mainly represented by two regions; the first region where the wall concentration is practically constant and equal to the injected one and the second region where the concentration varies approximately as the inverse of the distance from the injection slit. It is shown that the increased wall length is directly related to the thickening of the viscous sublayer. The wall concentration distribution is related to the drag reduction and a simple correlation between its values and the characteristics parameters of the external flow and the drag reducing injection can be established.