The random wave current forces on vertical slender circular cylinder were investigated in this paper. An appropriate definition of KC number is given. By using Morison Equation, the force on cylinder by both irregular wave and current is analyzed. Based on model test data and the mean square error method, the relationship between drag force coefficient Cd Inertia force coefficient Cm. lift force coefficient (CL) max. (CL)1/3 and KC number IS also given. The relationship of characteristic lift force value with characteristic inline force In wave-current coexsting field is discussed.


Slender vertical circular cylinder is one kind of typical element be used In coastal and offshore engineering structure. So far Morison equation is the practical method to be used commonly for the calculation of inline force and bas been extended for various usage. For the coexisting field of wave and current. Morison equation can also be used for the calculation of inline force. But almost no research on the problem of random waves forces coexisting with current on cylinder have been reported, especially on the lift force problem. The purpose of this study is to Investigate simultaneously lift force and Inline force on slender cylinder due to random waves and currents, including (I) the method tor analysis and investigation of the drag force coefficient Cd, inertia force coefficient Cm as well as lift force coefficient, (2) the dominant region of drag force, inertia force and intermediate region according to various KC number. (3) the character of lift and resultant force and the relationship between inline lift and resultant force. Model test was conducted in 892XI.8m wave current flume at Dalian University of Technology in which the wave generator from MTS company was installed which was controlled by PDP-11/24 mini-computer.

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