Some uncertainties and errors in wave force computations
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Copyright ©1979. Offshore Technology Conference. The present investigation examines several simplifications and hydrodynamic approximations commonly employed in wave force analyses. Alternatives and modifications are sought which improve the resolution of a general Morison approach. This is accomplished by considering two basic arrangements; a vertical cylinder and a horizontal cylinder in progressive waves. The physical differences between the flows are explored and the results are compared to previous planar harmonic flow measurements. It waa found that modifications to the usual Morison approach are required to adequately account for the orbital motions of the fluid and to account for the orientation of the orbits with respect to the cylinder axis. The consequences of this finding are discussed for inclined cylinders in waves and for cylinders in short-crested seas. The axial variations of the wave force on vertical cylinders are also examined in order to establish error bounds for the common practice of assuming constant values of C m and C D over the entire span. Lastly, the methods of computing force transfer coefficients from a force record are examined and sources of error are identified and briefly discussed.
author list (cited authors)
Ramberg, S. E., & Niedzwecki, J. M.