Download or read book On Wakes in Stratified Fluids written by Gerald S. Janowitz and published by . This book was released on 1967 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt: The paper considers two-dimensional flow induced by a body moving with constant speed through a linearly stratified fluid. The solution shows a diffusive wake far upstream of the body. Less far upstream, a system of jets occurs; these jets become stronger and more narrow as the body is approached. An increase in speed or diffusivity weakens these jets. We find at low speeds, low diffusivities, and moderate distances upstream of the body, that the velocity along the x-axis given by the exact solution is well approximated by the upstream asymptotic nondiffusive solution. Far downstream of the body, the solution shows a diffusive wake identical with the far upstream diffusive wake. In the downstream region nearer the body, at high speeds, a wake exists which is similar to the homogeneous wake. At low speeds in this downstream region near the body, the solution shows a pattern of waves decaying in the downstream direction.

Download or read book Turbulent Wakes in a Stratified Fluid Part 1 Model Development Verification and Sensitivity to Initial Conditions written by W. S. Lewellen and published by . This book was released on 1974 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: A 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.

Download or read book Numerical Investigation of Momentumless Wakes in Stratified Fluids written by Kyle Ashley Brucker and published by . This book was released on 2009 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: The dissertation focuses on a comparison between momentumless (self-propelled) and net-momentum (towed) wakes with an emphasis on the elucidation of buoyancy effects. It is difficult to realize truly momentumless wakes in the laboratory and DNS offer a viable, accurate alternative because the initial value of net momentum can be controlled and the evolution of the net momentum can be closely monitored. DNS of axisymmetric wakes with and without net momentum are performed at Re=50,000 on a grid with approximately 2 billion grid points. The development of the wake is characterized by the evolution of maxima, area integrals and spatial distributions of mean and turbulence statistics. The mean velocity in the self-propelled, momentumless wake decays more rapidly than the towed case due to higher shear and consequently a faster rate of energy transfer to turbulence. Buoyancy allows a wake to survive longer in a stratified fluid by reducing the u1'u3' correlation responsible for the mean-to-turbulence energy transfer in the vertical direction. This buoyancy effect is especially important in the self-propelled case because it allows regions of positive and negative momentum to become decoupled in the vertical direction and decay with different rates. The vertical wake thickness is found to be larger in self-propelled wakes. The role of internal waves in the energetics is determined and it is found that they are responsible for sustaining turbulence at the wake periphery long after the shear production has subsided. The non-equilibrium region of the Re=50,000 wake is found to exhibit a time span when, although the turbulence is strongly stratified as indicated by small Froude number, the turbulent dissipation rate exhibits inertial scaling. The multiply inflected mean velocity profile, inherent to the self-propelled wake, results in four bands of vorticity, compared to the two bands observed in the towed case. Vortex pairs of opposite sign form vortex dipoles which interact with other dipoles to cause a more disordered appearance of the late wake vorticity when compared to the towed case.

Download or read book The Growth of a Turbulent Wake in a Density stratified Fluid written by Walter P. M. van de Watering and published by . This book was released on 1966 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 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).

Download or read book Turbulent Wakes in Density Stratified Fluids of Finite Extent written by Edmund A. Prych and published by . This book was released on 1964 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results are presented of an investigation of the effects of a free surface and density stratification of the turbulent transfer of mass and momentum in two-dimensional wakes. The effect of depth of submergence on the drag of a twodimensional body was also investigated.

Download or read book Formation and Collapse of Turbulent Wakes in Stratified Fluids written by Roy Hayden Monroe and published by . This book was released on 1968 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Near Wake of Bluff Bodies in Stratified Fluids and the Emergence of Late Wake Characteristics written by and published by . This book was released on 2010 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary goal of our work was to provide accurate information about velocity and density field in the near wake region of a flow around a sphere in a stratified fluid. This is a canonical configuration used in investigating a structure of stratified wakes and in numerical simulations.

Download or read book Second Order Turbulent Modeling Applied to Momentumless Wakes in Stratified Fluids written by W. Stephen Lewellen Milton Teske and published by . This book was released on 1973 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: The technique of second-order closure for turbulence modeling is used to treat the growth and decay of turbulence, and the generation of internal waves behind a submarine moving at constant velocity through a stratified ocean. A computer model based on the solution of five partial differential equations and approximating nine others is generated. Required model coefficients are obtained by comparison with data obtained from laboratory flows and the atmospheric surface layer. The model is verified by comparison with Naudascher's wake data in the limit of vanishing stratification; with Wu's observations in the limit of starting with a uniformly mixed region in a strongly stratified fluid; and with Hartman and Lewis's analytical predictions in the limit of a small perturbation to the ambient linear density gradient and vanishing turbulence. (Modified author abstract).

Download or read book Turbulent Wakes in a Stratified Fluid Part II User s Summary Guide to Wake Computer Program written by Milton Teske and published by . This book was released on 1974 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: This 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.

Download or read book The Shape of Two dimensional Turbulent Wakes in Density stratified Fluids written by Roy Hayden Monroe and published by . This book was released on 1968 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of an analytical and experimental investigation of the rate of growth of the zone of turbulent mixing behind a two-dimensional circular cylinder are presented. The analytical phase of the study formulated a dynamical model for a parcel of fluid subjected to inertia, turbulent damping, and gravity restoring forces. The experiments were conducted in a tank 120 in. long and 4.5 in. wide which was filled to a depth of 18 in. with a fluid having a linear density gradient. The cylinder was towed at mid-depth by a variable speed motor-pulley system. A record of wake growth behind the cylinder was made by means of motion pictures of an aluminum pigment tracer in the fluid. The Reynolds number ranged from 1300 to 3500 and densimetric Froude numbers varied from 5 to 20. The density stratification was found to exert a strong inhibiting force on the wake growth. Using the dynamical model to correlate experimental data, the mixing length in the turbulent zone was found to decrease with increasing density stratification. (Author).

Download or read book Two dimensional Turbulent Momentum Wakes in Density Stratified Fluids written by Robert Anton Froebel and published by . This book was released on 1964 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Wake Deformation in Density stratified Fluids written by Harihara Iyer Padmanabhan and published by . This book was released on 1969 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Decay of Stratified Turbulent Wakes Behind a Bluff Body written by Karu Chongsiripinyo and published by . This book was released on 2019 with total page 255 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mixing of a Stratified Fluid in a Two dimensional Turbulent Wake written by Edmund A. Prych and published by . This book was released on 1963 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experiments on Turbulent Wakes in a Stable Density stratified Environment written by Walter P. M. van de Watering and published by . This book was released on 1969 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a laboratory experiment, turbulent mixed regions were generated in a linearly density-stratified fluid and their behavior was studied. Such regions may occur in nature in the atmosphere and in the ocean. Particularly during their early history, the shape of such regions is influenced by the interacting effects of turbulence and buoyancy, culminating in the occurrence of a maximum thickness and subsequent vertical collapse. A Richardson number (equivalent to the ratio of the characteristic turbulence time and the Vaisala period) was found satisfactorily to correlate the data obtained, together with those previously obtained by other investigators with self-propelled bodies. An estimate is made of the degree of mixing that takes place inside a turbulent mixed region during its growth in stably-stratified surroundings: the effectiveness of this mixing determines the ultimate thickness to which the mixing region collapses. (Author).

Download or read book The Shape of Two dimensional Turbulent Wakes in Density stratified Fluids written by and published by . This book was released on 1968 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of an analytical and experimental investigation of the rate of growth of the zone of turbulent mixing behind a two-dimensional circular cylinder are presented. The analytical phase of the study formulated a dynamical model for a parcel of fluid subjected to inertia, turbulent damping, and gravity restoring forces. The experiments were conducted in a tank 120 in. long and 4.5 in. wide which was filled to a depth of 18 in. with a fluid having a linear density gradient. The cylinder was towed at mid-depth by a variable speed motor-pulley system. A record of wake growth behind the cylinder was made by means of motion pictures of an aluminum pigment tracer in the fluid. The Reynolds number ranged from 1300 to 3500 and densimetric Froude numbers varied from 5 to 20. The density stratification was found to exert a strong inhibiting force on the wake growth. Using the dynamical model to correlate experimental data, the mixing length in the turbulent zone was found to decrease with increasing density stratification. (Author).

Download or read book Small scale Instabilities in Trailing Wake Vortices in a Stratified Fluid written by Donald P. Delisi and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: