The forces and moments on a UUV hull undergoing unsteady sway motions are analyzed using both traditional methods which integrate the pressure and shear stress at the wall, and hydrodynamic impulse based methods which analyze the vortical structure of the flow around the body. Computational fluid dynamics simulations have been conducted of a body with a slenderness ratio of 8.5, at a Reynolds number of 3.4 million, undergoing a variety of sway maneuvers. These include steady translations at incidence angles from 0${}^{\circ }$ to 20${}^{\circ }$, impulsive acceleration with varied initial incidence, and sinusoidally oscillating sway over a range of frequencies and amplitudes. The impulse based method is based on a body-fixed, non-inertial frame used to analyze the vortical structures near the body. It is demonstrated that this impulse based analysis provides a sensible decomposition of unsteady forces into those due to added mass and those due to unsteady circulation and motion history. Motion history effects are seen to be primarily described by the Lamb vector distribution around the body. These effects decay towards the quasi-steady limit at large times for impulsive motion and at low frequencies for sinusoidal motion. This is demonstrated with the analysis of the impulse based force components and with visualizations of the vortex structures in the flow field. A simplified form of the impulse based equations is derived and validated, based on approximations from slender body theory.

使用将壁上的压力和剪应力相结合的传统方法和基于流体动力脉冲的方法分析围绕身体的流动的涡流结构，对经历非定常摇摆运动的 UUV 船体上的力和力矩进行分析。已经对长细比为 8.5、雷诺数为 340 万的物体进行了计算流体动力学模拟，并进行了各种摇摆动作。这些包括从 0 入射角的稳定平移${}^{\circ }$ 到 20${}^{\circ }$，具有不同初始入射角的脉冲加速度，以及在一定频率和幅度范围内的正弦振荡摆动。基于脉冲的方法基于一个身体固定的非惯性框架，用于分析身体附近的涡旋结构。已经证明，这种基于脉冲的分析提供了不稳定力的合理分解，即由于增加的质量和不稳定的循环和运动历史。运动历史效应主要由身体周围的兰姆矢量分布描述。这些效应在脉冲运动的大时间和正弦运动的低频下向准稳态极限衰减。这通过基于脉冲的力分量的分析和流场中涡流结构的可视化得到了证明。