ANALYSIS OF WAVE FORCE ACTING ON THE MONOPILE BASED ON WAVE-POROUS SEABED-STRUCTURE COUPLED MODEL

To study the influence of the porous seabed, embedded depth and vertical downward velocity of the structure on the wave forces under wave action, the modified RANS equation with a κ-ε closure and Forchheimer saturation drag model are used to control porous flow, and fluid volume method (VOF) is used to track free surface. A three-dimensional coupled model of wave-porous seabed-structure is established. Firstly, reliability of the coupled model is validated, including wave attenuation reduced by porous seabed, turbulent flow around structure under wave action, and wave forces acting on the structure considering seabed porous characteristic. Then, parameters affecting the wave forces on the structure is analyzed, mainly including three aspects, which is wave conditions, porous seabed characteristics and structural properties. The numerical results show that, ignoring the porous characteristics of the seabed and simplifying it into rigid solids will underestimate the wave forces acting on the structure. Under larger height and longer periodic wave, wave forces action on structure in the deeper water is greater. Moreover, the wave forces acting on the structure are significantly affected by the porous characteristics of seabed, i.e., the porosity, particle size, the thickness. In addition, the influence of structural properties, such as diameter, cross section, embedded depth and vertical downward velocity on wave forces is also significant. Therefore, in engineering practice, wave conditions, porous seabed characteristics, embedded depth and dynamic movement of structure should be considered simultaneously to calculate the wave forces more accurately.