Experimental study of ship generated internal waves and associated phenomena

Internal waves generated by ships and submarines in a stratified water are studied experimentally in a laboratory wave-tank of 12 x 8 x 2 ft;The investigation has focused on the development of the experimental techniques on the measurement of internal waves; the systematic laboratory measurement of internal wave fields generated by a moving ship model; the kinematic and dynamic behaviors of the internal wave field. The study shows that the internal wave field generated by a moving ship is dominated by the first several waves which are due to the action of the ship-hull on the thermocline.;An experimental technique based on measurement of changes in averaged conductivity within a small water column was developed to measure internal wave amplitudes. The wave gauge can measure waves with height from less than tenth of a millimeter to centimeters.;Two basic cases are studied for a moving body: the subcritical case and the transcritical case. Experimental results show that a maximum in wave height is reached when the densimetric Froude number approaches unity. Internal wave amplitude spectra show that the internal wave spectra are contained in the region of kh less than 5, and a peak exists at kh ;The flow field around the moving body is visualized by applying Laser-Induced Fluorescence (LIF) technique. It is observed that internal waves are generated by several mechanisms. In the current study, they are body (or ship-hull), (ship) wake, and shear instability at the thermocline. The most prominent mechanism is by the body; only at large Froude numbers, do the ship's wake and shear instability play a role.;The investigation has provided insight with regard to both the kinematics and the dynamics of the internal wave field generated by a moving body. The experimental technique developed for internal wave measurement is recommended for further studies on internal waves.