Wake Collapse and Subsequent Generation of Internal Waves in a Density Stratified Medium
Wake Collapse and Subsequent Generation of Internal Waves in a Density Stratified Medium

Author: Jin Wu

Publisher:

Published: 1968

Total Pages: 106

ISBN-13:

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An experimental technique was developed to model a two-dimensional mixed region collapsing in a continuously density-stratified medium. The process of this mixed region can be divided into three stages. Empirical formulae were derived to describe the process of the first two stages, during which densimetric effects determine the modeling criterion. The collapse process in the final stage is complicated by viscous effects including mixing at the thin wake tip. The pattern of the internal waves generated by the initial impulsive collapse of the mixed region was studied; it can be represented by moving rays connecting either wave crests or troughs. These rays move away from the collapse center and at the same time decrease their slopes. A simpler steady state wave pattern generated by an oscillating plunger was also studied. Taken together, these experimental results are interpreted to show that the energy density of the initial impulsive collapse is skewed toward higher frequencies and that it is peaked at 8/10 of the Brunt-Vaisala frequency. The mechanism underlying the moving ray patterns is explained. (Author).

Flow Phenomena Caused by the Collapse of a Mixed Region in a Density-stratified Medium
Flow Phenomena Caused by the Collapse of a Mixed Region in a Density-stratified Medium

Author: Jin Wu

Publisher:

Published: 1966

Total Pages: 68

ISBN-13:

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Various phenomena are caused by the collapse of a mixed region in a model ocean; these include internal waves propagated in the linear-stratified medium below the thermocline, interfacial waves at the density-discontinuous interface (thermocline) and surface currents at the free surface. Results include the wave and orbital motions produced outside of the collapsing region for a number of different density stratifications. Regular internal waves of progressive oscillatory type propagating along the isopycnic lines can be scaled according to the length scale of the mixed region and the inverse time scale of the linear-stratified medium (Vaisala frequency of the medium). The value of the density jump at the thermocline determines whether the interfacial wave is characterized by the modeled thermocline and is essentially of a shallow water wave type, or is characterized by the lower stratified field and is essentially an internal wave distrubance. A series of divergences or convergences (surface sloshing currents) was observed at free surface; the general pattern of these currents shows that the water particles oscillated sinusoidally with time at each station, and that particles separated by approximately half an interfacial wave length oscillated exactly out of phase. (Author).