Abstract： In this paper, a two dimensional flow around a riser and the one attached with axial-rod shrouds were investigated using discrete vortex method (DVM) respectively. It is shown that at different shroud numbers,  shrouds can suppress the drag and lift coefficients, and vortex shedding to some extent, except for the case of 4 rods number with 45° inflow. The large number of rods achieves better suppression effect. Compared with the results of 10 rods with 4 rods,  it is shown that the 10-rod shroud is less sensitive to the inflow direction than the 4-rod shroud. For the 10-rod shroud, both time-averaged drag coefficient and fluctuating lift coefficient are less than those of the corresponding bare cylinder with a reduction up to about 26% and 79% respectively. DVM can be useful for the research of flow of circular cylinder and flow suppression because of its quick, simple, and reliable features.
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