Effect of peak perforation on flow past a conic cylinder at <Emphasis Type="Italic">Re</Emphasis>=100: drag,lift and Strouhal number

A flow past a circular-section cylinder with a perforated conic shroud, in which the perforation is located at the peak of the conic disturbance as the shroud installed on the cylinder and uniformly distributed with several circular holes, is numerically simulated at a Reynolds number of 100. Two factors in the perforation are taken into account, i.e. the attack angle relative to the direction of incoming flow and diameter of holes. The effect of such perforation on the drag, lift and vortex-shedding frequency is mainly investigated. Results have shown that variation of the attack angle has a little effect, especially on the drag and vortex-shedding frequency, except in certain cases due to the varied vortex-shedding patterns in the near wake. The increasing hole diameter still exhibits a little effect on the drag and frequency of vortex shedding, but really reduces the lift, in particular at larger wavelength, such as the lift reduction reaching almost 66%–68% after introducing the perforation.