Equations of Motion for a Float Supported Craft in a Seaway

With the aid of Lagally's theorem for unsteady flow, Taylor's theorem relating added masses to doublets, and strip theory, the forces and moments produced by an arbitrary potential flow field, which is slowly varying in space, on a slender float, free to move in all six degrees of freedom, were determined in terms of the strip-wise added mass distribution. In addition estimates of the contributions of the free surface to the effect of variations in the wetted length are also made. These results, together with estimates of viscous drag, and buoyancy forces, are then incorporated into the equations of motion of a craft supported by an arbitrary number of such floats. By the use of first order wave theory and linearization of the above described relationships the equations of motion are put in a form suitable for computing various statistical quantities useful in describing the behavior of tilt float supported craft in a confused sea. (Author).