Modeling Breaking Ship Waves for Design and Analysis of Naval Vessels

Prediction of the performance and non-acoustical signature of surface ships which feature such effects as breaking waves, spray and air entrainment is still beyond the capabilities of standard numerical solution methods. The near-field flow about a surface ship is characterized by complex physical processes such as: (i) spray sheet and jet formation; (ii) strong free-surface turbulence interactions with (large-amplitude) breaking waves; (Hi) air entrainment and bubble generation; and (iv) post-breaking turbulence and dissipation. These physical phenomena still require resolutions that are not feasible in practical engineering flows, despite continuing advances in computational resources. A two-pronged approach is proposed to develop methods to accurately predict these complex physical systems. First, physics-based closure models for steep breaking waves in the presence of turbulence are developed with results from high-resolution direct numerical simulations of the Navier-Stokes equations. Second, cutting-edge parallel computing capabilities and newly developed solution techniques are utilized to simulate the free-surface flow around naval combatants moving at high speed. Direct numerical simulation is used to simulate an ensemble of breaking waves at moderate Reynolds numbers. Information derived from the breaking events in this study is being used as a first step in evaluating closure models for inclusion in existing LES and "off-the-shelf" RANS capabilities. Using NFA (numerical flow analysis), full scale simulations of a DDG model were performed. The simulations capture such features as wave breaking and air entrainment which are quantitatively compared to experimental results