||Breakwaters are the maritime structures which are generally extending to both sides of the ship channel. Their main functions are to create the shelter, prevent the heavy seas, and maintain the stability of the harbor basin to ensure safety of navigation and cargo operation. The Port of Taichung and the Port of Mailiao are the important ports in the middle of the west coast of Taiwan. According to the results of the sounding datum survey in 2014, the maximum depth of the seabed scouring in the vicinity of these two ports found was 26 m, and part of the amors of breakwater have been collapsed and backwards. Therefore, it is a top priority task to take appropriate responses and improving measures.|
In this paper, three dimensional numerical simulations of wave-current fields around both heads of breakwaters of the Port of Taichung and the Port of Mailiao were carried out. The purpose is to explore and analyze the characteristics and scouring mechanism around the head of breakwater. The boundary conditions and initial inputs were established by using statistics to analyze background data and compare with the wave-current and seabed scouring characteristics of this research. The tools applied in the research are FAVORTM, wave, tide, turbulence and scouring modules in the Computational Fluid Dynamics (CFD) software FLOW-3D○R which calculate hydrodynamics.
The results show that numerical simulations of flow hydrodynamics of wave-flow field is consistented with field observations and laboratory experiments. By visualizing, it distributes the free surface wave, vertical flow conditions, and the maximum orbital velocity at the seabed that shear in the eddy area to clarify the scouring mechanism around the head of breakwater. Including the wave-induced flow field, along a north-south trend of the flooding and ebb current, and the steep slope formed together. Because the wave propagation is blocked by the breakwater, the accumulated hydrodynamic energy turns to the deep sea and cause of band-like offshore flow mixed with the southward forward wave, which deepen the turbulence mechanism of the seabed boundary layer. Turbulence mechanism by the suspension load, with the trend and move away. Due to the lack of long-term lack of sand source, the scouring area is difficult to achieve balance of siltation, thus continue to threaten the stability of the breakwater structure.