**Jialong Jiao \* and Songxing Huang**

School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510641, China; 201820107670@mail.scut.edu.cn

**\*** Correspondence: jiaojl@scut.edu.cn; Tel.: +86-139-2514-6963

Received: 10 April 2020; Accepted: 28 April 2020; Published: 29 April 2020

**Abstract:** Accurate prediction of ship seakeeping performance in complex ocean environment is a fundamental requirement for ship design and actual operation in seaways. In this paper, an unsteady Reynolds-averaged Navier–Stokes (RANS) computational fluid dynamics (CFD) solver with overset grid technique was applied to estimate the seakeeping performance of an S175 containership operating in bi-directional cross waves. The cross wave is reproduced by linear superposition of two orthogonal regular waves in a rectangle numerical wave tank. The ship nonlinear motion responses, bow slamming loads, and green water on deck induced by cross wave with different control parameters such as wave length and wave heading angle are systemically analyzed. The results demonstrate that both vertical and transverse motion responses, as well as slamming pressure of ship induced by cross wave, can be quite large, and they are quite different from those in regular wave. Therefore, ship navigational safety when suffering cross waves should be further concerned.

**Keywords:** ship hydrodynamics; ship motions; green water on deck; slamming; cross wave; CFD
