The effect of boundary shear flow on hydrodynamic forces of a pipeline over a fully scoured seabed
The effect of boundary shear flow on hydrodynamic forces of a pipeline over a fully scoured seabed
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边界剪切流对完全冲刷海底管道水动力的影响
DOI：
10.1016/j.oceaneng.2020.107326
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发表时间：
2020
影响因子：
5
通讯作者：
Wang Shuqi
中科院分区：
文献类型：
--
作者：
Chen Linfeng;Wang Yitao;Sun Shiyan;Wang Shuqi
采用基于剩余流的大涡模拟方法，数值研究了边界剪切流对完全冲刷海底管道水动力的影响。本文应用广义-α方法求解了Navier-Stokes方程的变分多尺度方程，并采用了基于残差的湍流模型。研究中考虑了与实验参数相同的流动。基于残差的大涡模拟程序计算的水动力与实验结果吻合较好。通过与流过平坦海床上圆柱体的水流的比较，研究了冲刷坑引起的水流变形特性及其对水动力的影响。结果表明，冲刷坑使通过差距的流速降低，旋涡脱落减弱，拖曳力减小，升力均方根值减小，沿沿着海床的水动力减小。特别地，在研究中考虑了具有不同边界层厚度的流动。结果表明，边界层厚度对圆柱的流动特性和流体力学特性有明显的影响。随着流动边界层厚度的增加，圆柱下游的涡的尺寸变大，涡度变小。随着边界层厚度的增加，平均阻力、升力、升力均方根值和斯特劳哈尔数明显减小。此外，圆柱下游涡量等值线和升力均方根值的变化表明，随着流动边界层厚度的增加，旋涡脱落变得很弱。边界层厚度对沿着海床的水动力影响很小。
The effect of boundary shear flow on hydrodynamic of a pipeline over a fully scoured seabed is numerically investigated by residual-based large eddy simulations. A generalized-α method is applied to solving variational multiscale formulations of the Navier–Stokes equations with a residual-based turbulence model. Flows with the same parameters as the experiment are considered in the study. The hydrodynamic forces computed by the in-house codes of the residual-based large eddy simulations are in good agreement with the experimental results. Characteristics of the flow distorted by the scour hole and its effect on hydrodynamic forces are examined by comparisons with the flow past a circular cylinder over a flat seabed. The results show that the scour hole causes lower velocity through the gap, weaker vortex shedding, smaller drag force, smaller RMS of lift force and smaller hydrodynamic forces along the seabed. In particular, the flows with different boundary layer thicknesses are considered in the study. It is found that the boundary layer thickness has evident effect on the flow characteristics and hydrodynamics of the cylinder. The size of the vortices downstream the cylinder become large and their vorticities become small as the boundary layer thickness of the flow increases. The mean drag, lift, RMS of lift and Strouhal number clearly decreases with the boundary layer thickness. Additionally, the variation of the vorticity contours downstream the cylinder and RMS of lift indicate that the vortex shedding become weak as the boundary layer thickness of the flow increases. The boundary layer thickness has little effect on the hydrodynamic forces along the seabed.