Abstract

A floating body exposed to the action of incident waves experiences second order forces due to nonlinear effects, apart from the oscillatory loading components which cause the first-order motions of the body. These forces which are derived by the solution of the linearized body-wave interaction problem, performs zero mean values over one period. These second-order force components are known as mean drift forces. They are generally small in magnitude compared to their first-order counterparts, however, they may cause large excursions of the body from its mean position, in situations where there is a lack or very small hydrostatic restoring forces (Mavrakos, 1988).
So far, two principally different approaches have been presented in the literature for the determination of the mean drift forces. One is based on the application of the momentum conservation principle (Sclavounos, 1987; Molin, 1983; Mavrakos, 1995 to name a few), while the other is based on the direct pressure integration over the instantaneous wetted surface of the body. The latter method is applied herein, keeping all relevant terms up to second order. It has been introduced by Pinkester & VanOortmersen (1977), whereas Molin (1983) and Papanikolaou & Zaraphonotis (1987) extended the method by adding some missing terms regarding the vertical drift components and the pitch and roll drift moments. Other similar studies on mean drift forces using the direct integration method are Konispoliatis & Mavrakos (2014, 2021) and Konispoliatis et al. (2021).