Numerical Analysis of the Dynamic Effects of Ballast Tank Water Discharge on Submarine Motion Stability During Emergency Rising

Submarine emergency surfacing involves complex dynamic behaviors because of the shift in the center of gravity (CG) and changes in the moment of inertia caused by ballast tank water discharge. This study proposes a numerical analysis model based on six-degree-of-freedom (6DOF) equations of motion to investigate the dynamic behavior of submarines during emergency surfacing. A grid-based Volume Cell model was developed to simulate the water flow dynamics within the ballast tank, incorporating the effects of mass displacement and inertia changes into the equations of motion. The simulation results indicated that linear motions (surge, sway, and heave) are minimally affected by the discharge of ballast tank water. Nevertheless, rotational motions (pitch and yaw) are significantly influenced by the discharge, particularly due to the reduction in inertia. In pitch motion, the sensitivity to external moments increases, resulting in a noticeable increase in angular deviation. The proposed model showed high accuracy through comparisons with theoretical calculations and CAD modeling results, providing a robust foundation for optimizing the design and placement of ballast tanks. This paper presents a novel methodology to enhance the reliability and efficiency of emergency surfacing simulations, offering valuable insights and design guidelines for improving submarine stability and performance during critical operations.