Equilibrium scour depth at offshore monopile foundation in combined waves and current

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• 作者：WenGang Qi (1)
  FuPing Gao (1)
  
• 关键词：monopile ; pore ; pressure ; scour depth ; combined waves and current ; Froude number
• 刊名：SCIENCE CHINA Technological Sciences
• 出版年：2014
• 出版时间：May 2014
• 年：2014
• 卷：57
• 期：5
• 页码：1030-1039
• 全文大小：
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• 作者单位：WenGang Qi (1)
  FuPing Gao (1)
  
  1. Key Laboratory for Mechanics in Fluid Solid Coupling Systems, Institute of Mechanics, Chinese Academy of Sciences, Beijing, 100190, China
  
• ISSN：1869-1900

文摘

Unlike the pier scour in bridge waterways, the local scour at offshore monopile foundations should take into account the effect of wave-current combination. Under the condition of wave-current coexistence, the water-soil interfacial scouring is usually coupled with the pore-pressure dynamics inside of the seabed. The aforementioned wave/current-pile-soil coupling process was physically modeled with a specially designed flow-structure-soil interaction flume. Experimental results indicate that superimposing a current onto the waves obviously changes the pore-pressure and the flow velocity at the bed around the pile. The concomitance of horseshoe vortex and local scour hole around a monopile proves that the horseshoe vortex is one of the main controlling mechanisms for scouring development under the combined waves and current. Based on similarity analyses, an average-velocity based Froude number (Fr a) is proposed to correlate with the equilibrium scour depth (S/D) at offshore monopile foundation in the combined waves and current. An empirical expression for the correlation between S/D and Fr a is given for predicting equilibrium scour depth, which may provide a guide for offshore engineering practice.