Instability and turbulence in density-stratified mixing layers. by William David Smyth Download PDF EPUB FB2
Browand, F. & Winant, C. Laboratory observations of shear-layer instability in a stratified fluid. Bounary Layer Met. 5, Brown, G. & Roshko, A. On density effects and large structure in turbulent mixing layers.
A vertically symmetric, stably stratified mixing layer may exhibit, depending upon the details of the initial profiles of horizontal velocity and density, either of two major classes of linear, supercritical instability.
This book is an introduction to the application of nonlinear dynamics to problems of stability, chaos and turbulence arising in continuous media and their connection to dynamical systems.
Turbulence resulting from Kelvin–Helmholtz instability in layers of localized stratification and shear is studied by means of direct numerical simulation.
Our objective is to present a comprehensive description of the turbulence evolution in terms of simple, conceptual pictures of shear–buoyancy interaction that have been developed previously based on assumptions of spatially uniform stratification and by: Motivated by the importance of stratified shear flows in geophysical and environmental circumstances, we characterize their energetics, mixing and spectral behaviour through a series of direct numerical simulations of turbulence generated by Holmboe wave instability (HWI) under various initial by: 9.
Self-organized criticality of turbulence in strongly stratified mixing layers to fully developed turbulence in the stratified mixing layer is in any significant way determinant of diapycnal.
Kelvin-Helmholtz instabilities are the most commonly studied type of instability in sheared density stratified flows. Turbulence caused by these instabilities is an important mechanism for mixing in geophysical flows.
The primary objectives of this study are the evolution of these instabilities and quantifying the mixing they generate using direct numerical simulations.
The. 3L: Abstract The problem of flow instability and turbulence is reexamined for the case of free mixing layers and jets. It is argued that some rather simple stability considerations can describe the flow development whether the flow is fully turbulent or not.
Particular consideration is given to the subharmonic feedback. Since wind speed and turbulence often are subject to a diurnal change, also the mixing layer height changes with the same periodicity.
Typical is the formation of a ground (height some meters) inversion in the early morning due to cooling of the earth by outgoing radiation. Later, when the ground warms up.
Turbulence resulting from Kelvin-Helmholtz instability in layers of localized stratification and shear is studied by means of direct numerical simulation. Our objective is to present a comprehensive description of the turbulence evolution in terms of simple.
Direct numerical simulations of turbulence resulting from Kelvin–Helmholtz instability in stably stratified shear flow are used to study sources of anisotropy in various spectral ranges.
The set of simulations includes various values of the initial Richardson and Reynolds numbers, as well as Prandtl numbers ranging from 1 to 7. Our focus is on turbulence in density-stratified environments and on the irreversible fluxes of tracers that actively contribute to the density field.
Various papers on turbulence and coherent structures are presented. Among the topics addressed are: emergence of characteristic motion in homogeneous turbulent shear flows, generation of coherent structures in free shear layers, use of the proper orthogonal decomposition in a plane turbulent mixing layer, 3D dynamics of coherent structures forming Author: Olivier Metais, Marcel Lesieur.
In some cases, these instabilities induced flows can transition to turbulence. Both the spatial and temporal criteria to achieve the transition to turbulence have been examined. Finally, a description of the energy-containing scales in the mixing layers, including energy “injection” and cascade processes are presented in greater by: The constants h 0, Δu, and Δρ represent the initial thickness of the shear layer and the associated changes in velocity and density; R is the ratio of shear layer thickness to stratified layer thickness ().
In order to obtain a turbulent flow efficiently, we add to the initial mean profiles a perturbation field designed to stimulate both two-dimensional primary and three Cited by: Rayleigh–Taylor (RT) and Richtmyer–Meshkov (RM) instabilities play an important role in a wide range of engineering, geophysical, and astrophysical flows.
They represent a triggering event that, in many cases, leads to large-scale turbulent by: Rayleigh–Taylor (RT) and Richtmyer–Meshkov(RM) instabilities are well-known pathways towards turbulent mixing layers, in many cases characterized by significant mass and species exchange across the mixing layers (Zhou, Physics Reports, –, 1–).Cited by: Two simple turbulent shear flows, namely a surface jet and a mixing layer, under the influence of stable gravity stratification, were investigated experimentally.
The shear flows were generated in the laboratory by letting fresh water flow over saline water in Cited by: A conceptual framework for analysing the energetics of density-stratified Boussinesq fluid flows is discussed.
The concept of gravitational available potential energy is used to formulate an energy budget in which the evolution of the background potential energy, i.e. the minimum potential energy attainable through adiabatic motions, can be explicitly by: Direct numerical simulations of turbulence resulting from Kelvin–Helmholtz instability in stably stratified shear flow are used to study sources of anisotropy in various spectral ranges.
The set of simulations includes various values of the initial Richardson and Reynolds numbers, as well as Prandtl numbers ranging from 1 to 7.
We demonstrate that small-scale anisotropy is Cited by: 1. Introduction. Molecular mixing in response to stirring by turbulence is an important process in many practical applications. When the microscopic densities of the fluids participating in the mixing are very different, these flows have been referred to as variable density (VD) flows in contrast to the Boussinesq approximation in which the densities are Cited by: We study the processes through which three dimensional turbulence develops in stratified free shear layers and the impact of various secondary instabilities on the efficiency of the mixing process.
The efficiency of irreversible mixing, as compared to reversible "stirring", is determined by the extent to which, relative to the increase in kinetic energy, background Author: A.
Mashayek, W. Peltier. Compressibility and heat release effects in high-speed reactive mixing layers I.: Growth rates and turbulence characteristics Combustion and Flame, Vol. Investigation of strut-ramp injector in a Scramjet combustor: Effect of strut geometry, fuel and jet diameter on mixing characteristicsCited by: Rayleigh–Taylor (RT) and Richtmyer–Meshkov(RM) instabilities are well-known pathways towards turbulent mixing layers, in many cases characterized by significant mass and species exchange across the mixing layers (Zhou, Physics Reports, –, 1–).Cited by: It describes turbulence in the mixed boundary layers at the sea surface and seabed, turbulent motion in the density-stratified water between, and the energy sources that support and sustain ocean mixing.
Little prior knowledge of physical oceanography is by: The mixing layer is a flow of paramount importance for understanding the development of turbulence in external aerodynamics or combustion, as well as in atmospheric or oceanic flows.
These so-called “spatially-growing mixing layers” are characterized by the formation of big spiral vortices resulting from a Kelvin-Helmholtz type by: 3. Going by this, boundary layer is also a form of shear layer.
But in boundary layer the momentum transport is affected by a solid interface and viscous forces are dominant upto some distance. In case of a shear layer forming at a parallel fluid flow interface the viscous forces are not dominant and.
Rayleigh–Taylor and Richtmyer-Meshkov instability induced flow, turbulence, and mixing. I Article (PDF Available) in Physics Reports September with Reads.
This work is aimed at understanding the physics of wallbounded compressible reacting mixing layers. Linear instability is analyzed with a special emphasis on the effects of bounded walls. Three groups of unstable modes are found in both non-reacting and reacting flows when the relative Mach number is : Dongshin Shin.
direct numerical simulations of turbulence arising from the dynamic instability of stably stratiﬁed shear layers.1,2 The work is motivated by the need to properly interpret measure-ments of turbulent events in the Earth’s oceans; however, the results have important implications for a wide range of tur-bulent ﬂows.Turbulence in both homogeneous and stratiﬁed mixing layers has been the object of many laboratory experi-ments,28–33 theoretical studies34–41 and numerical simula-tions–52 Observational studies have conﬁrmed the util-ity of the stratiﬁed mixinglayer modelin interpretinggeo-physical mixing processes.5–7,53 Turbulence generation.'An Introduction to Ocean Turbulence by Steve Thorpe is the first book addressing the needs of instructors teaching introductory courses in ocean mixing.
After initial explanations of turbulence fundamentals and techniques for measuring it in the ocean, the emphasis shifts to the processes producing the turbulence and how they in turn are 4/5(1).