Experimental Investigation of the Laminar Boundary Layer Flow on a Rotating Wavy Disk

Since nearly one century, the flow on a flat rotating disk has provided the paradigm for studying rotating flows. For the laminar flow regime, a self-similar solution was obtained by von Kármán [6] in 1921, and a rather special feature of his exact solution of the Navier-Stokes equation is a constant boundary layer thickness not depending on the radial coordinate. A substantial modification of this canonical configuration is given by a wavy disk with a sinusoidal surface shape. Although axis-symmetric, no exact solution for the laminar flow on a wavy disk is known so far. In this study, detailed measurements of the velocity profiles were performed within the laminar boundary layer flow on a wavy disk. Based upon the experimental data, the potential of a self-similar solution approach for describing the resulting flow field was assessed. It was found that such an approach is useful for approximating the far-field solution but systematic deviations were observed in the vicinity of the disk origin.