Computational study on near wake interaction between undulation body and a D-section cylinder

We present a numerical study on the hydrodynamic performance of undulation NACA0012 foil in the near wake of D-section cylinder. Computations are conducted using unsteady incompressible Navier-Stokes equations with a moving adaptive mesh based on laminar flow. Investigations are focused on the effect of distance ratio between foil tip and centre of cylinder (L/D≤2.0) on the thrust/drag performance of foil and cylinder at various foil undulation frequency (St). We found that, foil thrust coefficient (Ct) increases considerably with the appearance of cylinder and an optimal distance exists at which Ct reaches maxima. The maximum increment is about eleven times that of its counterpart of single foil, which is obtained at St=0.23 and L/D=0.5. Our results for the cylinder drag coefficient (Cd) observed the existence of optimal parametric map, combined with various gap ratios and foil frequencies. With these parameters, insertion of an undulation foil can significantly lead to the drag reduction indicating that undulating foil could work efficiently as a passive vortex control device for cylinder drag reduction.