Investigation of wave loads on structures floating in polynya by hybrid green function method

The paper demonstrates a hybrid Green function method for investigating wave loads acting on a structure floating in polynya enclosed by an ice sheet. A vertically virtual surface, stretching from the ice edge to the seabed, is designated as the control surface to divide fluid domain into two subdomains. In the interior polynya with a free surface, an upper surface condition for diffraction potential is derived, and the simple Rankine source is employed to construct boundary integro-differential equation (BIE) over free surface, body surface and control surface. On the other hand, in the exterior fluid domain beneath ice, the Green function, which inherently satisfies ice-covered water surface, radiation and seabed conditions, is adopted. So the corresponding integro-differential equation is only imposed over vertically virtual surface. Interior and exterior BIEs are discretized and solved simultaneously through implementing the continuity condition between the two subdomains. In this solution, analytical and semi-analytical schemes are utilized to determine influence coefficients related to Rankine source and ice-covered Green function. Numerical simulations are carried out for the wave loads on a submerged sphere as well as a FPSO floating in polynya, and the effects of ice thickness and water depth are analyzed. The good concordance with available published results indicates that our developed approach is reliable for investigating wave interactions with structures in polynya.