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对圆柱附加固定整流罩的已有研究表明,它在降低升阻力和抑制涡激振动方面有优良的效果。但固定整流罩具有方向敏感性,当来流方向改变后效果会受到显著影响,甚至起到增加升阻力和加剧涡激振动的反作用。本文给圆柱附加了圆弧直径为40mm,形状夹角α分别为30°、45°、60°、75°和90°五种尺寸的旋转整流罩,并进行了风洞实验。其中整流罩可以自由地围绕圆柱轴线旋转。实验结果表明:旋转整流罩在流体力产生的力矩作用下,旋转至一个偏离尾流中心线固定角度的动态平衡位置,而平衡位置偏转角δ随着形状夹角α的增大而增大。附加旋转整流罩后,相对单圆柱能够提高尾迹区域压力,并能使时均阻力和脉动升力分别在α=30°和α=75°时获得最大43.5%和67.0%的降低。此外,对于小α(α≤60°)情况,漩涡脱落频率明显高于单圆柱情况,而对于大α(α≥75°)情况,则与单圆柱情况相接近。所有旋转整流罩升力主频的幅值较之单圆柱有了很大程度的降低,可见旋转整流罩在抑制漩涡脱落方面有很好的效果。
Previous studies on cylindrical fixed fairing have shown that it has an excellent effect in reducing lift resistance and suppressing vortex induced vibration. However, the fixed fairing has the direction sensitivity, and the effect will be significantly affected when the flow direction is changed, and even the reaction to increase the lift resistance and aggravate the vortex vibration. In this paper, the rotating fairing with the diameter of 40mm and the included angle α of 30 °, 45 °, 60 °, 75 ° and 90 ° are added to the cylinder, and the wind tunnel experiment is carried out. Wherein the fairing is free to rotate about the cylinder axis. The experimental results show that the rotating fairing rotates to a dynamic equilibrium position at a fixed angle away from the centerline of the wake under the force generated by the fluid force, and the balance position deflection δ increases with the included angle α. With the addition of a rotating cowl, the relatively single cylinder increases the wake area pressure and achieves a maximum reduction of 43.5% and 67.0% for both the average and pulsating lift at α = 30 ° and α = 75 °, respectively. In addition, the frequency of vortex shedding is significantly higher for the case of small α (α ≤ 60 °) than for the case of a single cylinder, while for the case of large α (α≥75 °), the vortex shedding frequency is close to that for a single cylinder. The amplitude of the lift frequency of all the rotating fairings has been greatly reduced compared with that of a single cylinder. It can be seen that the rotating fairing has a good effect in suppressing the shedding of vortexes.