Steady wave longitudinal and lateral forces and yaw moment have significant influence on ship manoeuvrability in waves. The authors propose a method for predicting the steady wave forces and moment acting on ships manoeuvring in short waves using a modified formula for the wave amplitude near ships based on studies by Ueno et al. (2000, 2001). The authors clarify that the proposed method predicts less fluctuations in the steady wave forces due to a ship's forward speed, lateral drift, and yaw rate than did Ueno et al.'s original prediction. Moreover, the authors validate the method based on available experimental data.
The safety of a ship operating in seas depends on its manoeuvrability. Time-averaged values of higher-order wave forces, which slowly vary with the frequency of the manoeuvre (i.e., the steady wave force and moment), must be predicted accurately to evaluate ship manoeuvrability in waves. Experiments have shown that the steady wave longitudinal and lateral forces and yaw moment (hereafter referred to as "steady wave forces," including the yaw moment) depend not only on the ship speed but also on the drift angle and yaw rate (Suzuki et al., 2022; Ueno et al., 2000, 2001; Yasukawa and Adnan, 2006).
Recently, numerical prediction methods for steady wave forces considering the effects of drift angle and yaw rate have been developed using the time-domain Rankin panel method based on the near-field integration (i.e., the direct pressure integration around the ship surface) formula (Lee and Kim, 2020; Zhang et al., 2020). However, understanding the physical phenomena based on the computational results is difficult owing to mathematical complexity. The steady wave lateral force and yaw moment and the drift angle effects are significant in short waves (Suzuki et al., 2022; Yasukawa and Adnan, 2006). Thus, from a practical perspective, approximate treatments based on the physical interpretation would be required for short waves.