Xiuyuan Zhang

Bio: Xiuyuan Zhang is an academic researcher from Harbin Engineering University. The author has contributed to research in topics: Vortex shedding. The author has co-authored 1 publications.

Flow field characteristics of a two-dimensional moonpool under uniform flow conditions

Abstract: ABSTRACT Moonpools are holes in the middle of a ship's hull and through its deck. In this study, the flow mechanisms in moonpools in calm water were investigated. Star-CCM+ software was used to calculate the flow within a two-dimensional (2D) moonpool under uniform flow conditions. A 2D moonpool numerical calculation model was constructed, and the convergence analysis results and experimental data were used to verify the accuracy of the calculated results. Flow field and free surface fluctuations are the main factors that cause the drag force of the moonpool. The drag force increases with the flow velocity, and the drag coefficient presents different trends at different stages. With an increase in the Froude number, Fr, the 2D moonpool enters the frequency lock-in state of the piston and sloshing natural frequency. Additionally, increasing the moonpool length results in a nonlinear change in the flow state.

Numerical Study on Attitude and Resistance of a Side-Damaged Ship during Steady Flooding

Abstract: The computational fluid dynamics method is used to analyze the attitude and resistance of a side-damaged frigate DTMB-5415 during steady flooding phase. The volume of fluid method is used to capture the interface between water and air. The shear stress transport k-ω model is employed to include the turbulence effect. The dynamic overlapping grid method is utilized to deal with the mesh update due to the ship motion in the simulation. First, the resistance, floating position and wave profile of an intact ship for different forward speeds are calculated. By comparing the results with experimental data, the calculation method is verified. Then, the resistances, attitudes and flow fields for the ship in intact, side-damaged (symmetrical and asymmetric flooding) and damage-repaired conditions are calculated and compared. For the side-damaged condition, the main change of the ship’s attitude is that the ship’s sinkage increases as the forward speed increases. Compared with symmetrical flooding, the ship’s heel increases during asymmetric flooding, while the sinkage decreases. For symmetrical flooding, the resistance of the ship increases significantly compared to the intact ship case. The increased resistance is mainly caused by the increase of ship sinkage. The existence of opening that affects the flow field causes additional increase of ship resistance. The pressure resistance is the main component of increased resistance, which is similar to the asymmetric flooding case.