This study investigates analytically the influence of the length to draft and beam to draft ratio of a ship on the drift forces acting on a body in relatively short waves (small wavelength to ship length ratio). For validation, the proposed method is applied to predict the drift forces acting on simple geometries and real ships, yielding satisfactory predictions of the drift forces in both longitudinal and lateral directions. The proposed method can be applied to preliminary design tasks as it can capture the effect of the variation of a body's dimensional ratios and the influence of incident wave direction.
Recent years have seen diverse demands on the prediction of the steady second order wave forces and moments exerting on floating marine structures with or without forward speed. The side drift force and the drift yaw moment (and to a lesser degree the steady forces and moments in the other degrees of freedom) are essential for the simulation of ship's maneuverability in waves (IMO, 2013), for the design of mooring lines and the simulation of dynamic position of offshore support vessels and floating marine structures, etc. In the forward speed problem, the prediction of added resistance in waves is very important for propulsive performance analysis in realistic environmental conditions (ISO 15016, ISO 19030), thus, in relation to fuel consumption and greenhouse gas emission analysis.
Though alternative analytical and numerical methods are available for use in practice (e.g., for 2D problem Papanikolaou and Nowacki, 1980; for 3D problem Zaraphonitis and Papanikolaou, 1992), an efficient (fast, accurate and transparent) method, using minimum hull form information, is often desired. Under such background, analytical solutions based on potential flow theory (Molin, 1979; Chatjigeorgiou and Mavrakos, 2006; Duan et al., 2015; Liang and Chen, 2017), and empirical methods, often demonstrate an advantage in these tasks. For instance, in the prediction of added resistance, a popular approach is to apply potential flow nearor far-field methods, together with some semi-empirical correction for relatively short waves (Fujii and Takahashi, 1975), where the near- or far-field methods face challenges. Another approach is a pure empirical method, as developed by Liu and Papanikolaou (2020a, 2020b). To improve the performance of these methods, it is important to carefully examine the empirical correction components and establish a rational relationship between the empirical formula and hull form parameters.