斜向水流作用下海底管线周围水动力特性数值研究

Experimental Study on the Hydrodynamics Around Marine Pipelines Under Oblique Flows

管线附近的水动力因素是底床局部冲刷形成的主要原因。基于开源程序OpenFOAM和分离涡紊流模拟方法建立三维数值水槽,数值模型的计算结果与同条件的物理实验结果基本一致。在此基础上,对水流作用角为30°、45°、60°和90°及间隙比为0、0.1、0.3、0.5水流作用下,管线周围的流场结构进行分析,探讨水流作用角和间隙比对管线附近三维水流结构的影响规律。结果表明:随着作用角的增大,管前涡流范围逐步缩小至管线附近,管后涡流范围逐步向下游延伸,且管后涡漩尺度、回流范围与尾涡紊动区域逐步增加,尾涡中心逐步远离管线,且轴向水流逐渐减弱;管后尾涡的产生、脱落,涡旋尺度大小受管线与底床间隙比e/D的影响明显,e/D=0时管线后尾涡的脱落形态不明显;e/D>0.3时,类似圆柱扰流,管后尾涡形态变化不明显。

The hydrodynamic characteristics around marine pipeline are main causes of scour.A 3Dnumerical flume was developed based on the open-source software and the turbulence model of detached eddy simulation.The accuracy and reliability of numerical model was validated by laboratory results of velocity profile around pipelines.The influences of flow incident angle（30°、45°、60°and 90°）and the gap ratio（0、0.1、0.3、0.5）on 3Dhydrodynamic characteristics around pipeline wereanalyzed.SNumerical results show that3 Dhydrodynamic characteristics are gradually weakened,trailing vortex extending leeward and upward,and the turbulence region enlarging at upstream with the increase of flow incident angle;with the extension of gap radio,jet flow in the gap is gradually disappeared,fluid structure behind pipeline similar to the one behind cylinder under steady flow;obvious different fluid structure around pipeline is found in different region,distinct axial flow found at seaward and leeward of pipeline,nevertheless,the same flow direction to flow incident anglefound below pipeline.