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Effects of head loss, surface tension, viscosity and density ratio on the Kelvin–Helmholtz instability in different types of pipelines
Physica D: Nonlinear Phenomena ( IF 4 ) Pub Date : 2021-05-25 , DOI: 10.1016/j.physd.2021.132950
X.C. Yang , Y.G. Cao

We report the effects of head loss, surface tension, viscosity and density ratio on the Kelvin–Helmholtz instability (KHI) in two typical pipelines, i.e., straight pipeline with different cross-sections and bend pipeline. The dynamic governing equations for upper and lower fluids in the two pipes are solved analytically. We find in the straight pipeline with different cross-sections that the relative tangential velocity of fluid decreases with the increase of the head loss, viscosity and density ratio of upper and lower fluids, but it increases with the surface tension; the amplification factor decreases with the increase of the head loss and surface tension but increases with the density ratio of upper and lower fluids; the higher the height of fluid interface is, the more both the relative tangential velocity of fluid and the amplification factor are depressed. In the bend pipeline, the critical tangential velocity of fluid is found to decrease with the increase of the head loss, viscosity and density ratio of upper and lower fluids, but it increases with the surface tension; the amplification factor increases with the head loss and density ratio of upper and lower fluids, but it decreases with the increase of the surface tension; when the elbow angle is close to 80, the head loss reaches its maximum. The results provide guidance for pipeline design and theoretical prediction for flooding velocity in different types of tubes.



中文翻译:

不同类型管道水头损失、表面张力、粘度和密度比对开尔文-亥姆霍兹不稳定性的影响

我们报告了水头损失、表面张力、粘度和密度比对两种典型管道的开尔文-亥姆霍兹不稳定性 (KHI) 的影响,即具有不同横截面的直线管道和弯曲管道。解析求解了两管上下流体的动态控制方程。我们发现在不同截面的直管段中,流体的相对切向速度随着上下流体的水头损失、粘度和密度比的增加而降低,但随着表面张力的增加而增加;放大系数随着水头损失和表面张力的增加而减小,但随着上下流体密度比的增大而增大;流体界面的高度越高,流体的相对切向速度和放大系数被抑制得越多。在弯管中,发现流体的临界切向速度随着上下流体的水头损失、粘度和密度比的增加而降低,但随着表面张力的增加而增加;放大系数随着上下流体水头损失和密度比的增大而增大,但随着表面张力的增大而减小;当肘部角度接近 但随着表面张力的增加而降低;当肘部角度接近 但随着表面张力的增加而降低;当肘部角度接近80,水头损失达到最大值。研究结果为管道设计和不同类型管子淹没速度的理论预测提供了指导。

更新日期:2021-06-03
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