The Influence of a Free Surface on the Development of Turbulence in Submerged Jet
MICHIGAN UNIV ANN ARBOR DEPT OF AEROSPACE ENGINEERING
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Radar images of the ocean surface made when surface ships are moving within the imaged area reveal distinctive surface signatures attributed to the interaction of the turbulent wake of the ship with the free surface. In order to study the behavior of turbulence near a free surface, the flow in a round, turbulent jet issuing beneath and parallel to a clean free surface was investigated experimentally. A three-component Laser Doppler Velocimeter LDV was used to make detailed measurements of the mean flow velocity and Reynolds stress tensor throughout the flowfield. Surface shadowgraphs and Laser Induced Fluorescence LIF were used to visualize features of the free surface deformations and the subsurface flowfield. The jet Reynolds number, U sub e dv approximates 12,7000, and Froude number, U sub egh12 approximates 5.66, were comparable to those of the jet flow investigation of Bernal and Madnia, 1988. Large-scale turbulent structures within the jet generated surface waves that were observed to propagate nearly perpendicular to the jet axis. Measurements of the wavelength and wave speed from shadowgraph images showed these waves to be gravity-capillary waves.
- Fluid Mechanics