采用上游扰动体被动控制减阻技术的实验研究

通过风洞测压和水洞流动显示实验,研究了不同直径的扰动体尾迹下圆柱的流动结构和气动特性。结果表明当扰动体和圆柱串列布置时,流动呈现出两种流动模式:空穴流动和尾流撞击模式。当圆柱处于空穴流动模式时,其阻力可以大幅度降低。当扰动体直径为圆柱直径1/2时,圆柱阻力最大降低98%。综合绕流结构和圆柱表面压力分布的变化,指出阻力减小的原因主要是扰动体对圆柱前体的保护作用以及对后体流动的干扰作用,其中后者占主导地位。随着扰动体直径的增加,扰动体对圆柱前体的减阻效果增加。

Experimental studies on drag reduction of the circular cylinder with an upstream rod in tandem

The aerodynamics characteristics and the flow structure of the circular cylinder with an upstream rod in tandem were examined.The pressure distribution on the cylinder was obtained through the Hyscan2000 electronic pressure scanner in a wind tunnel,and the force was obtained by the pressure integration.The flow structure around the cylinder was visualized by the hydrogen bubble technique in a water tunnel.With the different stream-wise spacing ratio between the rod and the cylinder,the flow structures have two patterns: the cavity flow mode and the wake impinge mode.In the cavity flow mode,the drag of the cylinder was dramatically reduced by the upstream rod.With the rod diameter d/D=1/2(d and D are the diameters of the rod and cylinder,respectively),the maximum drag reduction of the cylinder is 98% that of the cylinder in free-stream.According to the flow structure and the pressure variation on different parts on the cylinder,the mechanism of the drag reduction of this passive control method was discussed.There are two reasons for the drag reduction method: one is the shield effect of the rod on the downstream cylinder,the other is the enhancement of turbulence intensity of the approaching flow.With the rod diameter increased,the latter has more contributions to the drag reduction.