Coupled hydrodynamic ship wake and PE-based acoustic propagation model

Abstract

A full-wave, one-way, 2D parabolic equation (PE) code is used to predict sound propagation through a complex hydrodynamic bubble field. The normalized velocity component obtained from a hydrodynamic ship wake model is the basis for constructing the bubble distribution. A three-dimensional field is used to represent the complex environment: down wake (toward or away from the ship), cross wake (perpendicular to the wake axis), and with depth. Although the hydrodynamic wake model generates three-dimensional wake-bubble fields, the PE program is a 2D model. The problem is assumed to be two-dimensional by taking various two-dimensional cuts of the wake field, which are then used in the PE simulation. The wake of a ship is a complicated and challenging environment in which to model acoustic propagation. Predictions are made for the representation of the wake at various distances from the source ship. From this study a few results are seen: (1) The sound level corresponding to the strength of a spherically spreading sound field can be obtained. (2) Sound propagation through the wake bubble field is a three-dimensional problem. (3) Small changes in void fraction can produce noticeable differences in the propagation. [Work supported by ONR under Award No. N00014-02-1-0156.]