黏土海床管道局部冲刷的模拟研究

基于黏土的流变特性,将黏土视为一种流体,用Herschel-Bulkley模型模拟,采用计算流体力学(CFD)软件Fluent建立二维管道冲刷模型,结合SST k-ω湍流模型以及VOF两相流模型对黏土海床上管道局部冲刷进行数值模拟研究。研究分析表明:海底管道的存在增加了海流对海床的剪切应力,随悬空高度增大,海床剪应力逐渐减小。管道冲刷深度主要受黏土的不排水抗剪强度和流场流速的影响,管道的局部冲刷深度随土体强度的增大而减小,屈服应力为150 Pa时其冲刷深度为0.63D,约为屈服应力为600 Pa时的2倍。管道的局部冲刷深度随流速的增大而增大,流速每增加0.2 m/s其管道下方的冲刷深度平均会增加0.16D。受管道对流场的扰动,管道下游的尾流冲刷深度对流场流速大小更为敏感。

Modering study on local scour of cohesive soil around submarine pipelines

The cohesive soil is considered as a fluid simulating with Herschel-Bulkley model based on the rheological properties of cohesive soil. The CFD software Fluent is adopted to study the two-dimensional pipeline scour,combining with the SST k-ω turbulence model and the VOF two-phase flow model to study pipeline local scour on the cohesive soil seabed. The result indicates that the existence of submarine pipeline increases the shear stress of current on the seabed,with the increase of suspended height,the shear stress of seabed decreases gradually. The scour depth of pipeline is mainly affected by the undrained shear strength of cohesive soil and the velocity of flow field,the local scour depth of pipeline decreases with the increase of soil strength as 150 Pa the scour depth is 0. 63 D,that is twice as much as that at soil strength as 600 Pa. The local scour depth of pipeline increases with the increase of velocity,for every 0. 2 m/s increase of velocity,the scour depth under the pipeline will increase by 0. 16 D on average. Due to the disturbance of the pipeline to the flow field,the wake scour depth of pipeline downstream is more sensitive to velocity of the flow field.