Abstract
The turbulent flow behind a dry-transom stern with a plunging water jet is numerically studied. High-resolution large eddy simulation (LES) is performed to predict the wave-elevation topology and vortex structure in the wake with varying jet height. The theoretical impact position between jet flow and stern wave is proposed. The turbulent wake under the stern-jet configuration can be divided as converging-corner-wave region (CCW), mixing region (MR), transition region (TR) and developed region (DR). High-speed plunging jet speeds up the averaged-axial velocity and enhances the shear effect near the free surface. The upward movement of the rooster tail is suppressed by the parabolic jet flow, and periodical large scale air pockets are clearly observed following the wake angle along the downstream direction. Air pocket vortices and jet vortices are merging in the near wake and forming U-shaped vortex structures. Reducing jet height accelerates the instability of coherent vortex structure and energy dissipation in the developed region. The main contributions in the power spectra density (PSD) spectrum of Turbulent Kinetic Energy appear in the frequency range of 10–20 Hz with the evolution of wake vortices.
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