Control of Drag Force on a Circular Cylinder using a Detached Splitter Plate

초록

Control of drag force on a circular cylinder using a detached splitter plate is numerically studied for laminar flow. A splitter plate which has the same length as the cylinder diameter(d) is placed horizontally in the wake region. Its position is described by the gap ratio(G/d), where G represents the gap between the cylinder base point and the leading edge of the plate. The drag varies with G/d; it has the minimum value at G/d=2.6 for the range of Reynolds number corresponding to the laminar vortex shedding. The drag reduction ratio achieved at Re=160 and G/d=2.6 was 24.3% compared with the case without the splitter, and 6.9% compared with the case where the splitter is attached to the cylinder, respectively. The vortex shedding is significantly suppressed by the splitter. Consequently the pressure in the near-wake region rises, yielding less drag on the cylinder. The drag sharply increases when the splitter is placed further downstream past the optimal G/d; this seems to be related to the sudden change in the bubble size in the wake region. This trend is consistent with the experimental observation currently available in case of turbulent flow.