Depth dependent added mass computations using impulse motion simulations for shallowly submerged vehicles, Part 2: Accelerating from steady forward velocity

Simulations of impulsive motion have previously been shown to accurately calculate depth dependent added mass at zero forward speed for underwater vehicles that are shallowly submerged. The simulation procedure, using high-fidelity CFD, produces added mass values at the infinite frequency limit while minimizing modeling assumptions that are present in lower-fidelity methods. The use of impulse-like simulations during parameter calculation results in shorter simulation times while simultaneously allowing for frequency independent parameters to be identified separately from memory effects. The present study extends the application of impulsive motion computations to cases that involve vehicle motions from an initial steady forward speed. Although they are independent of acceleration, calculated added mass values are shown to depend on both steady forward velocity and depth of submergence. Changes in the free surface elevation due to the creation of a Kelvin wave pattern alter the local submergence depth of the vehicle thereby affecting the added mass. The inclusion of viscosity and the presence of a viscous boundary layer is captured using steady-state simulations but is shown to have little influence on the added mass during a transient impulse-like maneuver. This viscosity independence is explained by the relatively small change in velocity from the nominal steady forward velocity and the focus on inertial effects by using small time scale simulations.