Author(s): Jisheng Zhang
Linked Author(s):
Keywords: Scour; Jacket foundation; Offshore wind turbine; Physical model; Numerical simulation
Abstract: Exploration of offshore wind energy has been a vital alternative to mitigate environmental pollution due to continuous consumption of fossil fuels. Among all types of foundation supporting the offshore wind turbines, the jacket foundation is well known for its application in mild and deep sea areas. Physical model tests were firstly conducted to investigate scour process around the jacket foundation under complex hydrodynamic loadings. In the cases of steady currents without foundation angle, local scour around the jacket foundation could be classified into three types, i.e., independent development type, weak interference type and strong interference type, based on the influence of flow intensity. With the increasing flow intensity and decreasing water depth, local scour intensifies although the maximum scour depth always occurs at the upstream side of front pile. However, the foundation angle would alter shelter effects from the front pile and make the maximum scour depth occur at the back pile or the middle piles. Compared to the steady current, the bi-direction currents would lead to a reduction about 20% in the maximum scour depth. The location of the maximum scour depth also alternately changed between the front and back piles. The effects from wave on local scour around the jacket foundation were also studied. For example, the maximum scour depth was found linearly related to wave height, water depth and wave period. For the combined wave-current conditions, scour process was divided into the clear-water scour and live-bed scour. In the case of clear-water scour, the maximum scour depth increased with an increasing KC number, which differs from that of live-bed scour. In addition to physical investigation, numerical techniques were also employed to study scour process around the jacket foundation. A scour numerical model for the jacket foundation was developed using the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations and the turbulence model. The sand bed sediment surface was handled using the immersed boundary method, and the wall shear stress was incorporated into the local scour simulation around the jacket foundation. This model has been validated based on the physical experiment in this work. The model properly reproduces the local scour around the jacket foundation.
Year: 2023