Hydrodynamic analysis of structures floating in polynya by multi-domain BEM using a combination of ice-covered and free-surface Green's function

A multi-domain boundary element method (BEM) is originally proposed to address hydrodynamic challenges associated with a structure floating in a polynya. This approach utilizes a control surface vertically extended from the interface of polynya and ice cover to seabed to separate entire fluid domain into two subregions. Ice-covered Green's function is adopted to establish boundary integral equation (BIE) in the outer region beneath ice sheet. And to enhance computational stability and efficiency, a semi-analytical scheme based on vertical line source distributing over vertical control surface is formulated to evaluate corresponding influence coefficients. Within inner polynya region, free-surface Green's function is employed, so BIE is merely imposed on structure and control surfaces. By discretizing the integral boundaries into a series of panels and enforcing the continuous conditions between the ice-covered and polynya regions, a coupled system of equations is formulated to solve velocity potentials on fluid domain boundaries of polynya. The efficacy of the multi-domain BEM is verified through calculations involving hydrodynamic coefficients of a cylinder structure that is submerged in the polynya, considering scenarios of negligible ice thickness as well as very small ice thicknesses. Then based on the multi-domain BEM, an extensive array of results and analyses are presented for a realistic offshore structure FPSO operating in polynya. Various configurations involving differing ice thicknesses, water depths and body drafts are thoroughly investigated.