The drag and lift characteristics of flow around a circular cylinder with a slit

Abstract

Flow past a circular cylinder with a slit results in local perturbation, which affects the flow pattern, vortex shedding and the aerodynamic forces. This study uses spectral element method to simulate flow past a cylinder with a normal slit or an inclined slit at Reynolds numbers of Re=100 to 500. For a cylinder with a normal slit, the drag and amplitude of the oscillating lift both increase as the width of the slit increases. There are two modes for a cylinder with an inclined slit: an injection mode and a blowing/suction mode. The drag also increases as the angle of inclination of the slit increases and is greater than that for a cylinder that has no slit for flow in the blowing/suction mode, except at low Reynolds numbers, such as Re=100. Increasing the width of slit or the angle of inclination of the slit increases the frequency of vortex shedding. However, a wider slit or larger angle of inclination also results in additional drag. There is a similarity between the external surface and the slit in that the aerodynamic forces due to pressure or shear stress vary with the angle of inclination of the slit.