Splitter-plate wake stabilisation and low aspect ratio cylinder flow-induced vibration mitigation

This paper investigates the proposed utility of splitter-plate wake stabilisation as a passive control mechanism for vortexinduced vibration (VIV) mitigation for low aspect ratio cylinders. Stationary cylinder experiments have repeatedly demonstrated the effectiveness of splitter plates in reducing lift and drag coefficients for a cylinder in uniform flow. Rigid attached splitter plates have been shown to be capable of completely eliminating vortex shedding in fixed cylinder investigations. In the limited number of studies that have examined the use of splitter plates in a system which is free to vibrate in the direction transverse to the flow, a galloping-type response has been reported. A range of splitter-plate ratios (l/D =0 to 4) was examined in this study over a reduced velocity interval of Ur = 3 to 60. A galloping-type response was observed with the addition of even small splitter plates to the cylinder. At small splitter-plate ratio (l/D), the response of the low aspect ratio cylinders appeared to be strongly influenced by vortex shedding, and key features such as the abrupt decrease in the galloping response at higher reduced velocity aligned well with the bare cylinder VIV response. With increasing splitter-plate ratio, there appears to be a smooth transition from pure VIV (i.e., at l/D = 0) to a galloping-type response heavily influenced by the vortex shedding at low reduced velocity and a predominantly galloping response at high reduced velocity. At higher splitter-plate lengths (l/D ≥ 28), no significant VIV or galloping-type response was observed.