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Author: Publisher: ISBN: Category : Languages : en Pages : 102
Book Description
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.
Author: Publisher: ISBN: Category : Languages : en Pages : 102
Book Description
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.
Author: Gerald S. Janowitz Publisher: ISBN: Category : Stratified flow Languages : en Pages : 111
Book Description
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.
Author: Kyle Ashley Brucker Publisher: ISBN: Category : Languages : en Pages : 180
Book Description
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.
Author: Jaime Klapp Publisher: Springer Science & Business Media ISBN: 3319001167 Category : Science Languages : en Pages : 471
Book Description
This book collects invited lectures and selected contributions presented at the Enzo Levi and XVIII Annual Meeting of the Fluid Dynamic Division of the Mexican Physical Society in 2012. It is intended for fourth-year undergraduate and graduate students, and for scientists in the fields of physics, engineering and chemistry with an interest in Fluid Dynamics from experimental, theoretical and computational points of view. The invited lectures are introductory in nature and avoid the use of complicated mathematics. The other selected contributions are also suitable for fourth-year undergraduate and graduate students. The Fluid Dynamics applications include oceanography, multiphase flows, convection, diffusion, heat transfer, rheology, granular materials, viscous flows, porous media flows and astrophysics. The material presented in the book includes recent advances in experimental and computational fluid dynamics and is well-suited to both teaching and research.
Author: W. S. Lewellen Publisher: ISBN: Category : Languages : en Pages : 134
Book Description
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.
Author: Tim C. Lieuwen Publisher: Cambridge University Press ISBN: 1139576836 Category : Technology & Engineering Languages : en Pages : 427
Book Description
Developing clean, sustainable energy systems is a pre-eminent issue of our time. Most projections indicate that combustion-based energy conversion systems will continue to be the predominant approach for the majority of our energy usage. Unsteady combustor issues present the key challenge associated with the development of clean, high-efficiency combustion systems such as those used for power generation, heating or propulsion applications. This comprehensive study is unique, treating the subject in a systematic manner. Although this book focuses on unsteady combusting flows, it places particular emphasis on the system dynamics that occur at the intersection of the combustion, fluid mechanics and acoustic disciplines. Individuals with a background in fluid mechanics and combustion will find this book to be an incomparable study that synthesises these fields into a coherent understanding of the intrinsically unsteady processes in combustors.
Author: Stanley A. Berger Publisher: ISBN: Category : Science Languages : en Pages : 330
Book Description
A comprehensive survey is given of the state of knowledge of steady, nonturbulent laminar fluid wakes behind both blunt and slender bodies in viscous fluids, with emphasis on high-speed wakes. The flows are generally assumed to occur at large but finite free-stream Reynolds numbers, generally with a thin boundary layer on the body. Compressible and viscous flow theory are involved. The focus is on basic theory and concepts; both experimental results and speculative theories are given only where they provide greater insight or information otherwise unavailable. Transition and turbulence problems are not discssed.
Author: Steven Weinberg Publisher: ISBN: Category : Languages : en Pages : 44
Book Description
Wake 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.
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Author: 
Author: Gerald S. Janowitz
Author: National Research Council
Author: Kyle Ashley Brucker
Author: Jaime Klapp
Author: W. S. Lewellen
Author: Tim C. Lieuwen
Author: Stanley A. Berger
Author: 
Author: Steven Weinberg