Pressure Distribution and Aerodynamics of Circular Cylinder with Freely Rotating Fairings
圆柱附加旋转整流罩表面压力分布及气动力特性

Previous study of flow around a cylinder with fixed fairing shows that it exhibits excellent effect on drag and lift reduction and vortex-induced vibration suppression.But fixed fairing is sensitive to flow derection.When inflow direction changes,its effect may not only be reduced but present retroaction,that is drag and lift are increased and vortex-induced vibration intensified.In present study,a rotating fairing with diameter D(40 mm) and five different shape angle α(30°,45°,60°,75° and 90° respectively) was designed,and wind tunnel test for the fairing was carried out.This fairing can freely rotate around cylinder axis.Experimental results show that the fairing may rotate around an off-axis deviated from the centerline of the wake which forms an equilibrium angle δ(on either side of wake) due to integrated effect of pressure difference along either side of fairing.Off-axis angle δ increases continuously with the increase of angle α,and reachs its maximum value 62° when α = 90°.Furthermore,it is concluded that both mean drag coefficient and root-mean-square fluctuating lift coefficient,that are largely determined by equilibrium angle,are less than that of corresponding bare cylinder and the reduction up to about 43.5% and 67.0% was obtained,respectively.In addition,for small α(α≤60°),vortex shedding frequency has a significant increase compared with bare cylinder.But for large α(α≥ 75°),the situation is almost similar to bare cylinder.The peak values of rotating fairing are much lower than that of bare cylinder,which indicates that the vortex shedding is suppressed significantly.