Unsteady computational fluid dynamics simulations of six degrees-of-freedom submarine manoeuvres
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Date
2012
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University of New Brunswick
Abstract
Submarine hydrodynamicists are continually striving to improve submarine manoeuvring
predictions in order to better understand operational limitations. Traditional
manoeuvring simulations use semi-empirical force estimation methods or captive model
experiments to predict hydrodynamic forces and moments on the manoeuvring submarine.
Semi-empirical methods are inexpensive and fast but not consistently accurate.
Coefficient-based models derived from captive model experiments are more accurate
but much more expensive. Time-history effects are also difficult to incorporate in
coefficient-based modelling and are thus often neglected. The effect of the seabed and
other passing vessels are also not included in traditional models.
In order to address these issues, an unsteady, six degrees-of-freedom (DOF),
Reynolds Averaged Navier-Stokes (RANS) submarine simulation approach has been
developed and applied to simulating the emergency rising manoeuvre and the interaction
between a submarine and a passing tanker. In this method, the 6 DOF motion
of the full-scale submarine is integrated simultaneously with the RANS solution for
fluid forces. Coefficient-based modelling is used for the propeller, control-surface deflections,
and ballast blowing in order to achieve economical solutions while accounting
for the important viscous effects. The submarine motion is integrated implicitly
using a robust predictor-corrector approach that uses a novel application of semiempirical
and coefficient-based models to accelerate convergence at each timestep. A
combination of sliding interfaces and mesh deformation is used to account for the relative motion between the tanker and submarine. Simulation results reproduce the
roll-instability observed for buoyantly rising submarines and provide insight on the
magnitude of the disturbance forces and submarine motions induced by a large tanker
passing over a diesel-electric submarine.