Subharmonic excitation of the shear layer between two ribs : vortex interaction and pressure field
Subharmonic excitation of the shear layer between two ribs : vortex interaction and pressure field
复制标题
两个肋之间剪切层的次谐波激励：涡旋相互作用和压力场
DOI：
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发表时间：
1991
期刊：
影响因子：
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通讯作者：
S. Inamdar
中科院分区：
文献类型：
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作者：
S. Acharya;T. Myrum;S. Inamdar
实验研究了在肋形管道流动中，亚谐强迫对肋骨后面弯曲的、再附着的剪切层的影响。在第一次亚谐强迫作用下，切变层中涡旋的形成变得规律化，但不发生配对。当流体在二次亚谐振处被强迫时，在重新连接之前，两个旋涡成对。这种配对伴随着显著的夹带和剪切层生长，这反过来又导致重新附着长度的显著缩短。当外力是气流中最大放大频率的第三次亚谐时，三个涡旋似乎在重新附着之前合并。合并过程被观察到是强烈的，并再次导致显著增强的夹带。相平均压力与旋涡的通过有关，当旋涡或旋涡对经过时，压头上方的压力减小，而当旋涡跨过压头时，压力增加。压力谱表明，初始涡动力学决定了所有强迫频率和流向位置的压力场，响应频率是配对前测量的固有频率。
Experimental study has been undertaken to examine the effect of subharmonic forcing on a curved, reattaching shear layer behind a rib in a ribbed-duct flow. With first subharmonic forcing, the vortex formation in the shear layer becomes regularised, but no pairing occurs. When the flow is forced at the second subharmonic, two vortices pair prior to reattachment. The pairing is accompanied by significant entrainment and shear-layer growth, which, in turn, leads to a dramatic reduction in the reattachment length. Three vortices appear to merge prior to reattachment when the external forcing is a third subharmonic of the most amplified frequency in the flow. The merging process is observed to be strong, and again leads to significant enhancements in entrainment. Phase-averaged pressures are shown to be related to the passage of the vortices with the pressure above a pressure tap decreasing as the vortex or vortex pair passes by it and the pressure increasing as the vortices straddle the tap. The pressure spectra indicate that the initial vortex dynamics dictate the pressure field, with the response frequency, for all forcing frequencies and streamwise locations, being the measured natural frequency prior to pairing.