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在平板上放置圆柱形成角区流动,利用布置在圆柱上游平板上的二维和三维槽道来控制或削弱角区马蹄涡,采用风洞试验和数值模拟开展研究。结果表明,二维和三维槽道均能推迟边界层的分离,使圆柱根部马蹄涡的强度减弱、尺度减小;同时槽道上游压力和逆压梯度均有所下降,槽道下游压力显著升高而逆压梯度总体降低。二维槽道对马蹄涡强度的削弱为61.15%~66.51%,而三维槽道对其削弱为66.65%~80.93%。讨论了三维槽道参数(包括槽道宽度、深度以及其中心线与圆柱中心距离)对控制效果的影响。槽道与圆柱的距离在对马蹄涡的控制中起主导作用。槽道控制的机理是,由于槽道的抽吸效应使得其上游靠近壁面的边界层中涡量较高的流体被卷吸入槽道形成槽道涡,槽道涡由三维槽道输运到下游。同时,随着槽道与圆柱的距离减小,更多的边界层流体流入槽道内。正是上述“槽道效应”使得槽道下游的逆压梯度降低,马蹄涡强度减弱,分离区范围减小。
Cylindrical angular zone flow was placed on the plate. The two-dimensional and three-dimensional channels arranged on the upstream plate of the cylinder were used to control or weaken the horseshoe vortex in the corner zone. Wind tunnel tests and numerical simulations were carried out. The results show that the two-dimensional and three-dimensional channels can delay the separation of the boundary layer, so that the strength of the horseshoe vortex at the root of the cylinder is weakened and the scale is reduced. Meanwhile, the upstream pressure and the reverse pressure gradient of the channel both decrease and the pressure in the downstream of the channel increases significantly High and adverse pressure gradient overall reduced. The two-dimensional channel weakens the strength of the horseshoe vortex by 61.15% -66.51%, while the three-dimensional channel weakens it by 66.65% -80.93%. The effects of three-dimensional channel parameters (including channel width, depth and distance between centerline and cylinder center) on the control performance are discussed. The distance between the channel and the cylinder plays a dominant role in controlling the horseshoe vortex. The mechanism of channel control is that the fluid with high vorticity in the boundary layer upstream of the wall is entrained into the channel to form a channel vortex due to the pumping effect of the channel. The channel vortex is transported to the downstream by the three-dimensional channel . In the meantime, as the distance between the channel and the cylinder decreases, more boundary layer fluid flows into the channel. It is the above “channel effect” that the back pressure gradient downstream of the channel is reduced, the strength of the horseshoe vortex diminishes, and the range of the separation zone is reduced.