Ocean Wave Forces on a Subsurface Sphere

There is an absence of field data for the surface wave-induced forces on a submarine, spherical structure. An ocean test site was established in 25 ft of water to measure the time histories of force exerted on an 8 in. sphere and the wave pressure interpretation of the surface elevation above the sphere. The data were recorded on shore and from the charts obtained drag coefficients were derived for 72 separate waves. Since the drag forces outweighed the estimated inertia forces for the waves processed, inertia coefficients could not be estimated from the records. It was found that the maximum total force range for the processed waves could be predicted with a correlation coefficient of 0.94 by using third-order theory to determine the water particle kinematics and by employing a single value of 0.69 for the drag coefficient, as estimated from the data, and a supposed value of 1.15 for the inertia coefficient.