Effect of free surface on submerged synthetic jet parallel to the surface

Abstract

The interaction of vortex rings with free surface is of considerable interest to the water vehicles like ships and other vehicle, which moves close to the water surface. The perturbation in the surface may also be useful for various applications. The Effect of free surface height on the submerged synthetic jet parallel to the surface in quiescent flow is studied experimentally. Flow visualization using Laser Induced Fluorescence (LIF) and mean stream wise and cross-stream wise velocities are taken by 5-Beam Laser Doppler Velocimetry (LDV) probe. This study is related to understand the vortex ring structure of synthetic jet and its effect on the free surface of water. Parameters for this study are, orifice diameter 13 mm at actuation frequencies 1 and 6 Hz. Three different water levels H = 1.5D, H = 3D and H = 5D from the center of the orifice are used for this study. Due to change in free surface height (H), it is observed that at frequency 1 Hz and water depth H = 1.5D, vortex rings drifted towards the free surface and create transverse surface waves during the interaction. Rebounding of vortex rings are also seen at frequency 6 Hz and water depth H = 1.5D. Velocity analysis shows that velocity normal to the surface reduces and velocity parallel to the surface increases as the vortex ring approaches the free surface. Previous studies on jets also suggest similar phenomenon for submerged jets.