In this paper computations are presented to investigate hydrodynamic interaction for large multiple submerged bodies in shallow water near free surface. This includes hydrodynamic calculations for single submerged spheroid, while hydrodynamic interaction for two and three submerged spheroids is also investigated. Computations for all above mentioned cases are made for different wave headings and water depths. Moreover, for multi-body case, computations are made for different separation distances. Calculations include motion RAO's (response amplitude operators) linearized forces and moments as well as second order mean drift forces and moments, in regular waves. Analysis reveals that wave heading, water depth and separation distance between the bodies are very important factors, which significantly affect the results.


Hydrodynamic analysis of wave action on multiple submerged bodies in shallow waters is one of the most demanding research fields in present offshore engineering. Presence of multiple submerged bodies in close proximity can cause forces of attraction or repulsion between the bodies. Moreover, hydrodynamic calculations become much more sensitive, when sea bed is close to the body. Therefore accurate prediction of hydrodynamic forces for offshore and ocean structures including multi-body interaction and shallow water effects is very important for a reliable structure design. However a relatively new and emerging concept is the use of three submerged pontoons for semisubmersibles and oil drilling platforms. Tri-hull ships are another practical example of this innovative concept. As far as hydrodynamic interaction for multiple submerged bodies in shallow water is concerned, presently, most existing works have not addressed this problem. For submerged bodies, some useful results are available in (Lee and Newman, 1991), and (Feng, Miao and Jiang, 1996), but these are mainly focused on single submerged body in infinite water depth case, and multi-body interaction effects or shallow water effects are not investigated.

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