Second-lrder Changes in Mean Surface Level and Long Period Motious of an Offshore Structure in Shallow Water

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The research on the second-order changes in mean surface level and long period motions of an offshore structs in shallow water have been done during the term of this project and the fellowing reslts have been obtained : 1)The second-order changes in local mean surface level induced by two-dimensional bichromatic radiation waves in an experimental flume with a paddel thpe wave maker have been investigated. From the numerical examples, it has been found that the free-wave vomponent plays an important roll in the evaluation of the local mean surface level. 2)The second-order diffraction problem for a fixed body in bichromatic waves has been solved exactly including the effects of second-order free wanes generated by a wave maker and it has been found that : a)The effects of the second-order velocity potential on the second-order long period wabe forces cannot ve neglected in shallow water. b)The reasonable prediction of second-order long wave forces.