Numerical analysis of a rotating cylinderwith spanwise discs

The aerodynamic characteristics of a rotating cylinder in cross-flow are investigated by means of Unsteady Reynolds Averaged Navier-Stokes simulations. For a cylinder configuration with endplates, the numerical simulations match the experimental trend for the force coefficients and the Strouhal number. Design parameters are studied including the ratio of circumferentialcylinder- velocity-to-freestream-velocity (a), the endplate diameter ratio and the cylinder aspect ratio. The incoming flow separates on each endplate edge and rolls up into two tip vortices that merge downstream. They impact considerably on the configuration performance particularly at high a. The tip vortices influence the cylinder flow topology especially for low aspectratio cylinders with small endplates. Finally, a cylinder configuration with spanwise discs isinvestigated for a < 3.4. The streamwise velocity component increases between the boundary laers of two facing discs thereby decreasing the effective spinning ratio. At the corner, the cylinder boundary layer thickness is reduced due to the radial flow component occurring on thedisc. Further, adding spanwise discs decreases the strength of the tip vortices. The combination of these three effects leads to a drag reduction at high a compared to a cylinder configuration without spanwise discs.