間隙比和嵌入比對黏土質海床管道局部沖刷特性影響研究

摘" " 要：本文基于有限體積法，采用Herschel-Bulkley黏土模型和VOF兩相流模型建立海底管道局部沖刷的二維CFD模型，以管道不同初始間隙比和嵌入比為變量參數開展數值模擬研究。通過分析管道兩側床面壓力特征、沖刷坑形態、阻力系數歷時曲線、管道局部速度分布等內容，揭示不同初始間隙比和嵌入比對海底管道局部沖刷特性影響的規律。研究結果表明：1）黏土質海床環境下海底管道局部沖刷受初始間隙比的影響顯著。隨著初始間隙比增大，管道兩側壓強差減小，管道局部極限平衡沖刷深度整體呈下降趨勢。初始間隙比越小，管道沖刷效應越顯著；初始間隙比越大，尾跡沖刷效應越顯著。2）黏土質海床環境下海底管道局部沖刷受初始嵌入比的影響顯著。隨著初始嵌入比的增加，管道局部極限平衡沖刷深度減小，沖刷坑的寬度減小。當管道初始嵌入比為0.1時，管道底部與海床之間的間隙難以形成。

關鍵詞：黏土；間隙比；嵌入比；海底管道；局部沖刷；CFD

中圖分類號：P75" " " " " " " " " " " " " " " " " " " 文獻標志碼：A

Study on the Influence of Gap Ratio and Embedding Depth on the Local Scour Characteristics of Clay Seabed Pipelines

ZHANG Meina，" HAN Xiangxi，" ZHAI Yu，" QI Guosheng，" REN Di，" MENG Zhanbin

（ Guangxi Key Laboratory of Ocean Engineering Equipment and Technology， Beibu Gulf University，" Qinzhou 535011， China ）

Abstract： In this paper， based on the finite volume method， a two-dimensional CFD model of local scour of submarine pipeline is established by using the Herschel-Bulkley clay model and VOF two-phase flow model， and the numerical simulation is conducted on the variable parameters of gap ratio and embedding ratio. The characteristics of bed pressure on both sides of the pipeline， scour hole morphology， resistance coefficient duration curve and local velocity distribution of the pipeline are analyzed， and the law of influence of gap ratio and embedding ratio on local scour characteristics of submarine pipelines is revealed. The results show that： （1） The local scour of submarine pipelines in a clay seabed environment is significantly affected by initial gap ratio. The local equilibrium scour depth of the pipeline shows an overall downward trend. The smaller the initial gap ratio， the more significant the pipeline scour effect. The larger the initial gap ratio， the more significant the wake scour. （2） The local scour of submarine pipelines in the clay seabed environment is significantly affected by the initial embedding ratio. With the increase of the initial embedding ratio， the local limit equilibrium scour depth and the width of scour hole decrease. When the initial embedding ratio of the pipeline is 0.1， it is difficult to form a gap between the bottom of the pipeline and the seabed.

Key words： clay;" gap ratio;" embedding ratio;" submarine pipeline;" local scour;" CFD

1" " "引言

海底管道被譽為“海上生命線”，承擔石油、天然氣等資源安全輸運的重任。然而，由于海床的不平整導致管道下方與床面之間存在一定的間隙，管道周圍流體對海底管道的局部沖刷會加劇管道懸跨。隨著懸跨段長度的不斷增加，海底管道除了受到自身重力作用以外，還會受到周期性渦激力的作用。這容易造成管道疲勞損傷甚至失效，并引發油氣泄漏事故而污染海洋環境。……