Centrifugal through-flow rotor-stator cavity boundary layer transition based on the effect of roughness

In this study, we report a set of compressible Reynolds-averaged Navier-Stokes simulation results of rotor-stator cavity flows under a range of conditions such as surface roughness, Reynolds number, and through-flow coefficient. The main objective is to determine the effect of rotor roughness on the characteristics of the fluid and thermal boundary layers. The boundary layer inside the disk cavity is found to be Batchelor-type within the present parameter range. Increases in Reynolds number, through-flow coefficient, and surface roughness all enhance the flow circulation inside the disk cavity. The thickness of the Ekman layer on the rotor is almost twice that of the stator Bodewadt layer. Rotor roughness significantly affects the turbulent characteristics of the flow when the rotor-stator cavity is rotationally dominated, but the effect is small when the cavity is through-flow dominated. Increasing rotor roughness accelerates the separation of the stator boundary layer, particularly at weak through-flow. On heat transfer, large rotor roughness induces an overall temperature rise in the cavity and reduces the thermal boundary layer thickness. The effects are more pronounced at low Reynolds numbers and small through-flow coefficient. The present results can facilitate the design of high-efficiency rotor-stator cavities.