Water entry is a highly non-linear transient flow problem, and it has a strong engineering application background. In this paper, a threedimensional numerical model for water entry of inclined cylinder with rotational degrees of freedom was established based on the overlapping grid method and dynamic fluid body interaction, whose reliability was verified by published experimental data. The results show that the rotational angular velocity cause the lateral displacement Y and change the closure and collapse mode of the cavity. As it increases, the dynamic characteristics and pressure distribution show a complex evolution under the effect of the cavity evolution.
Water entry means the structures enters free surface from air with various entry velocity and angle, whose phenomenon is extremely complicated. It is a highly nonlinear process and exists extensively in various engineering fields including (May, 1952; Faltinsen, 1990; Wei Shi and Wang, 2012).
In order to analyze the entire process of water entry, the experiment, numerical simulation and theoretical method were adopted to study this problem. Experimental approach could provide the most direct and effective research by particle imaging technology and high-speed photography. Worthington and Cole (1897) studied the evolution of cavity and shapes of sphere water entry by using a single-flash camera which is the earliest studies for entry problem. In recent years, Wei and Hu (2014), Aristoff and Bush (2009) and Shams, Jalalisendi and Porfiri (2015) analyzed the cavity evolution and motion characteristics for water entry of the cylinder, sphere and wedge respectively. In order to study the influence of surface wettability on water entry, the mechanism of water entry of the spheres and cylinders were carried out by Li, Zhang, Zhang, Huang, Ma and Wang (2019), Ueda and Iguchi (2012), and Korkmaz and Guzel (2017). Additionally, the researchers also conducted the entry experiments of various structures to analyze the physics mechanism and phenomenon from different aspects. (Yan, Pan, Shi and Wang, 2019; Zeraatgar, Malekmohammadi, Javaherian and Moradi, 2019; Yan, Pan, Shi, Chao and Zhang, 2018; Jalalisendi, Zhao and Porfiri, 2017).
