Interaction between long-crested random waves and a submerged horizontal cylinder

This paper is concerned with the interaction between long-crested random waves and a submerged horizontal cylinder in deep water. The analytical linear predictions are obtained by extending the classical linear solution for the diffraction of monochromatic waves by a horizontal submerged cylinder, to the random waves by applying the theory of wind-generated waves. It is obtained that the wave pressure, which represents a random Gaussian process, has an amplitude that increases on the upper half-cylinder and decreases on the lower half-cylinder, with respect to the wave pressure amplitude at the same depth in an undisturbed wave field. The random wave force is derived by integration of the wave pressure on the cylinder. Both the horizontal and the vertical force components have equal standard deviation and very narrow spectra. By applying the quasideterminism theory, is then obtained that both the wave pressure and the wave force on the cylinder, when a very high wave occurs, are quasi-impulsive in the time domain. Finally, the analytical predictions are compared with the data of a small-scale field experiment. It is shown that the linear theory well predicts the drop of the propagation speed of the wave pressure on the cylinder. Some discrepancies have been noted for the standard deviation of the random wave force, which is overestimated by analytical predictions.