Wake Collapse in a Stratified Fluid
Author: Carlton Louis Hindman
Publisher:
Published: 1974
Total Pages: 176
ISBN-13:
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Theory of Wake Collapse in a Stratified Fluid
Author: Timothy W. Kao
Publisher:
Published: 1975
Total Pages: 19
ISBN-13:
DOWNLOAD EBOOKA complete theory of the collapse of a wake in the form of a two-dimensional circular mixed region of uniform density in a linearly stratified fluid is given. The initial stage is based on existing theories and the principal stage is based on the concept of a quasi-steady density current in a stratified environment. The two stages are properly matched. The dimensionless time at the initiation of the principal stage is theoretically determined. The theoretical finding is in excellent agreement with previous numerical and experimental results.
Wake Collapse in a Stratified Fluid: Linear Treatment
Author: Harold W. Lewis
Publisher:
Published: 1971
Total Pages: 14
ISBN-13:
DOWNLOAD EBOOKThe problem of wake collapse in an incompressible, linearly stratified fluid with no boundaries is solved in the linear Boussinesq approximation. (Author).
Final Stages of Wake Collapse in a Stratified Fluid
Author: Steven Weinberg
Publisher:
Published: 1973
Total Pages: 44
ISBN-13:
DOWNLOAD EBOOKWake collapse in a stratified fluid is studied in the linear approximation with particular attention to the late stages of its decay. For an infinite ocean with a constant Vaisala frequency, any smooth disturbance will eventually decay as the minus three halves power of t. An apparent discrepancy between this result and the work of Hartman and Lewis is traced to the sharp discontinuity in their initial conditions. The normal modes for a realistic problem with an ocean surface and bottom and a varying Vaisala frequency are treated by methods developed in potential scattering theory, and the results are then used to estimate the behavior of the disturbance at late times.
Wake Collapse and Subsequent Generation of Internal Waves in a Density Stratified Medium
Author: Jin Wu
Publisher:
Published: 1968
Total Pages: 106
ISBN-13:
DOWNLOAD EBOOKAn 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).
Collapse of Turbulent Wakes in Density-stratified Media
Author: Jin Wu
Publisher:
Published: 1965
Total Pages: 50
ISBN-13:
DOWNLOAD EBOOKThe wake generated by a submerged body moving through a density-stratified medium consists not only of a region of turbulence but also of a region of water with homogeneous density. The purpose of the present research is to study phenomena and modeling criteria relating to the collapse of this wake. Since the wake is very slender in the direction of the body passage, this problem is simplified by studying only the collapse of a particular transverse section of the wake. An experimental technique was successfully developed by using a wall-mixer to model the collapsing phenomen of a two-dimensional wake in densitystratified media. The process of collapse can be divided into three stages: 'initial', 'principal' and 'final' collapse stages. Empirical formulae were derived to describe the collapse processes of the first two stages, during which the gravitational effect is found to be the predominant modeling criterion. The collapsing process in the final stage was complicated by the increasing viscous effect and observed mixing at the thin wake tip. (Author).
The Growth of a Turbulent Wake in a Density-stratified Fluid
Author: Walter P. M. van de Watering
Publisher:
Published: 1966
Total Pages: 116
ISBN-13:
DOWNLOAD EBOOKThe force of gravity causes a turbulent wake in a density-stratified fluid to eventually cease its vertical growth and then to collapse towards its horizontal midplane. In the present investigation this phenomenon was studied experimentally. The turbulent wake was created by means of a spiral paddle, agitated by a pendulum-type arrangement outside a transparent lucite tank. Data were obtained from tracings of the motion pictures taken by a 16 mm movie camera. Both the pendulum arrangement and the paddle diameter were varied to find the possible influence of the experimental conditions. It was observed that the initial rate of growth in the vertical direction is constant, depending primarily on the density gradient and the agitation mechanism (i.e. pendulum and paddle diameter). This initial rate of growth of the wake, the maximum vertical thickness of the wake, the time at which collapse begins and the turbulence intensity within the wake at that time, were all correlated with the Vaisala frequency, resulting in three important constants which seemed to be independent of the experimental conditions. (Author).
Turbulent Wakes in a Stratified Fluid. Part II: User's Summary Guide to 'Wake' Computer Program
Author: Milton Teske
Publisher:
Published: 1974
Total Pages: 117
ISBN-13:
DOWNLOAD EBOOKThis document is a part of the final report on Contract N00014-72-C-0413 covering the period May 15, 1972, to June 30, 1974 and contains the user information needed to operate the WAKE program on the A.R.A.P. Digital Scientific Corporation META-4 computer system. Part I of this report summarizes the turbulent model derivation and verification, and the sensitivity of the wake collapse to changes in initial conditions.
Some Comments on the Modeling of the Collapsing Wake
Author: E. Y. T. Kuo
Publisher:
Published: 1972
Total Pages: 12
ISBN-13:
DOWNLOAD EBOOKThe problem of scaling the phenomena of the collapse of the wake of a self-propelled body in a stratified fluid is examined. Conditions are derived such that the Froude number (based on body speed, length and Vaisala period) is equal for both model and prototype. Conditions are also obtained for the existence of buoyancy and inertial subranges in the wake turbulence. These conditions are applied to determine the smallest size model for which the phenomenon of wake growth and collapse is properly scaled from the prototype. (Author).
Turbulent Wakes in a Stratified Fluid. Part 1: Model Development, Verification, and Sensitivity to Initial Conditions
Author: W. S. Lewellen
Publisher:
Published: 1974
Total Pages: 134
ISBN-13:
DOWNLOAD EBOOKA computational model has been developed for the turbulent wake of a body moving through a stably stratified fluid. Details of the wake growth, collapse and generation of internal waves were examined by the application of a second-order closure approach to turbulent flow developed at A.R.A.P. over the past few years. Predictions of the model have been verified by comparison with a wide variety of wake flows including wakes with no momentum, wakes with axial momentum, wakes with angular momentum, and for wakes in both stratified and unstratified fluids. A sensitivity investigation reveals that the primary variable affecting the strength of the generated internal waves is the initial Richardson number, with the first local maximum of the vertical height of the wake scaling inversely with the 1/8th power of the initial Richardson number.
