Influence of wave-current interaction on hydrodynamic forces acting on a fixed marine structure
2013
Kimura, H. (Kochi University, Nankoku, Kochi (Japan)) | Kamii, Y.
Marine structures like cylindrical bridge piers are exposed to hydrodynamic force F (=Fsub(M)+Fsub(D), where, Fsub(M) is mass force and Fsub(D) is drag force) exerted by wave and current. While wave generates Fsub(M) and part of Fsub(D), current generates residual part of Fsub(D). F is calculated by Morison's formula. Ocean current velocity u is broken down into steady flow velocity v and fluctuating wave velocity vsub(w) cos omegat (where, vsub(w) is half amplitude horizontal velocity of wave, angular velocity omega = 2pi/T, T is wave period and t is time). Drag force Fsub(D) (= Fsub(D)+ Fsub(D), where, Fsub(D) is steady drag force and Fsub(D) is fluctuating drag force) has been calculated by Fourier transform. Conclusions are as follows : (1) Steady drag force Fsub(D) acting on a structure, which is primarily generated by steady velocity v, increases under the existence of fluctuating velocity vsub(w) cos omegat. (2) Fluctuating drag force Fsub(D) acting on a structure which is primarily generated by vsub(w), increases in the same frequency components as that of wave under the existence of steady velocity v.
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