3 edition of structure of velocity and density interfaces in a weakly turbulent stratified shear flow found in the catalog.
Written in English
|Statement||by Gregory M. Powell.|
|The Physical Object|
|Pagination||xii, 212 leaves :|
|Number of Pages||212|
(). Turbulence structure in thermal convection and shear-free boundary layers. (). Turbulence, waves and mixing at shear-free density interfaces. Part 1. A theoretical model. (). Turbulent air flow over hills and waves. (). Velocity fluctuations near an interface between a turbulent region and a stably stratified layer. (). This study is motivated by the importance of the stratified turbulence in geophysical flows. We present a theoretical analysis of the buoyancy subrange based on the theory of strongly stratified turbulence. Some important turbulent scales and their relations are explored. Scaling constants of the buoyancy subrange scaling laws for both kinetic and potential energy spectra are .
In a stratified flow, a large scale shear flow can often dominate the overall structure of the flow, and evolves slowly in time. It is called the Vertically Sheared Horizontal Flow (VSHF). This shear flow is characterized by vertical variation only, without vertical velocity. Anselmet F, Gagne Y, Hopfinger E J and Antonia R A High order velocity structure functions in turbulent shear flows, J. Fluid Mech. Crossref Antonia R A, Browne L W B and Kim J Some characteristics of small scale turbulence in a turbulent duct flow, J. Fluid Mech.
The nature of the flow, laminar or turbulent, is captured very efficiently in a single parameter known as the Reynolds number. where is the density of the fluid, the local flow velocity, a characteristic length describing the geometry, and is the viscosity of the fluid.  The Reynolds stress of a flow is the covariance of horizontal (u ′ and v ′) and vertical (w ′) velocity deviations from the mean flow, and is a measure of the turbulent momentum flux. The high‐frequency sampling rate of the ADV allows direct measurements of Reynolds stress with a high degree of accuracy [ Voulgaris and Trowbridge.
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The structure of velocity and density interfaces in a weakly turbulent stratified shear flow by gregory m. powell a dissertation presented to the graduate council of the university of florida in partial fulfillment of the requirements for the degree of.
TABLEOFCONTENTS PAGE ACKNOWLEDGEMENTS iii LISTOFFIGURES vi LISTOFSYMBOLS viii ABSTRACT xi CHAPTER I INTRODUCTION 1 Motivation 1 Two-LayerFlows 3 ARegimeConceptForTwo. The structure of velocity and density interfaces in a weakly turbulent stratified shear flow Powell, G. Abstract. The mixing region between two parallel and homogeneous streams of fluid having different densities and velocities was investigated.
The flow was produced in a flume with a test section m long, m high and m wide by Cited by: 2. The structure of turbulent density interfaces 47 which allowed profiles of temperature and salinity to be temperature was measured using a copper-constantan thermocouple, one junction being traversed vertically whilst the other was kept in a constant-temperature by: [TD] also identify two kinds of stratified flow: stratified smooth (SS) and stratified wavy (SW).
These waves, as they say, “are produced by the gas flow under conditions where the velocity of gas is enough to cause waves to form, but slower than that needed for the quick wave growth which leads transition to intermittent or annular flow. Townsend, A. Turbulent flow in a stably stratified atmosphere J.
Fluid Mech. 3, – Townsend, A. The Structure of Turbulent Shear Flow, 2nd edn. Cambridge University Press. Turbulent mixing across a density interface is a common occurrence in geophysical flows and it affects the vertical exchange of contaminants between the two layers in stratified flows.
Besides the environmental and geophysical problems, practical problems such as the design of industrial equipment involve stratified phenomena and the.
Three-dimensional model is used to predict distribution of air velocity, temperature and turbulent kinetic energy.
In stratified shear flows the modeling of vertical disturbances is most important. To assess the potential of a flow structure like that shown in Fig.
18 to develop turbulence, we employ the well-known methods for stability analysis of a stratified parallel shear flow based on the Taylor–Goldstein equation. This requires the assumption that unstable modes are short in comparison with the horizontal scale of the ISW, so that.
Krylov, A.D. () Laboratory study of the density interface structure in a shear flow. In: The annual international session of the WG “Laboratory modelling of dynamic processes in the ocean”, Abstracts, Moscow, Institute for problems in mechanics, Russian Academy of Sciences, Google Scholar.
The velocity variation over an eddy of L T = m in a flow with a velocity shear of s −1 is 1 m s −1. This is comparable, but not greater than, background speeds suggesting that it might influence the degree of isotropy by straining eddy structure in the horizontal direction.
A parallel, stratified shear layer approximates the background flow profiles that produce shear instability in the equatorial ocean (Smyth et al.): where h is the half-thickness of the layer, and Δ U and Δ B are the half-changes in velocity and buoyancy (Figs. 5a,b). On vertical mixing and the energy transfer from the wind to the water.
Tel Linden, P. The interaction of a vortex ring with a sharp density interface: a model for turbulent entrainment.
Journal of Fluid Mechan Lofquist, K. Flow and stress near an interface between stratified liquids. Physics of Fluids 3. The velocity fields of a turbulent wake behind a flat plate obtained from the direct numerical simulations of Moser et al. () are used to study the structure of the flow in the intermittent.
The turbulent air–water interface and flow structure of a weak, turbulent hydraulic jump are analyzed in detail using particle image velocimetry measurements. The study is motivated by the need to understand the detailed dynamics of turbulence generated in steady spilling breakers and the relative importance of the reverse-flow and breaker shear layer regions with attention to.
The buoyancy effects on the turbulence structure in unstably‐stratified shear flow generated by cooling the top of the layer in an open channel were investigated. Measurements were made of the characteristics of the turbulent fluctuations; turbulence intensities, correlation coefficients, joint probability density functions, and coherence‐phase relationships.
lent energy spectrum and scale with flow thickness. Turbulent kinetic energy reaches a maxi- mum in the shear layer at the upper boundary of the flow where the large eddies are generated and is at a minimum near the velocity maximum where fluid shear is low.
Introduction Many geophysical flows occurring at the Earth's surface are driven by. Motivated by the tendency of high Prandtl number fluids to form sharp density interfaces, we investigate the evolution of Holmboe waves in a stratified shear flow via direct numerical simulation.
Like their better-known cousins, Kelvin-Helmholtz waves, Holmboe waves lead the flow to a turbulent state in which rapid irreversible mixing takes place. We present a series of three-dimensional visualizations of numerically simulated turbulent wakes in a stably stratified fluid with a focus on the effects of the wake Reynolds number, Re, on the wake flow.
The visualization of stratified wakes is complicated by the coexistence of regions of distinct dynamics in the flow, including large-scale ‘pancake vortices,’ small-scale shear.
Stratified Kelvin–Helmholtz instability. The stratified Kelvin–Helmholtz instability (KHI) test case is a famous problem which manifests itself when there is a velocity difference at the interface between two fluids of different densities (Thomson, ).It can commonly be observed through experimental observation and numerical simulation, and it is also visible in many.
Stably stratified wall-bounded turbulence is commonly encountered in many industrial and environmental processes. The interaction between turbulence and stratification induces remarkable modifications on the entire flow field, which in turn influence the overall transfer rates of mass, momentum, and heat.the interaction between the turbulent gas flow and the interfacial waves.
This approach includes two steps. First, we derive a flat-interface base state. This comprises a velocity profile that takes account of the laminar sublayer present in the near-interfacial region of the gas, and a method for determining the wall and interfacial shear.An equivalent Poiseuille's Law is derived for a homogeneous isotropic turbulent field.
The derivation is based on an analogy between momentum transfer and heat and mass transfer, three coefficients being used to characterize the exchange process: (1) the molecular viscosity µ, (2) an intensity parameter to characterize the magnitude of the turbulent velocity fluctuations ν 2.