Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 21 for “"Shear Instabilities"”.
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Shear instabilities between accretion disks and nova objects
… on the pre-explosion stage, investigating how shear instabilities and accretion-driven dynamics affect the boundary layer between the accretion disk and the stellar surface. The main goal is to assess how shear-driven mixing modifies the thermodynamic and structural conditions of this region …
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Shear instabilities in stellar objects: linear stability and non-linear evolution
Shear flows have a significant impact on the dynamics in various astrophysical objects, including accretion discs and stellar interiors. Due to observational limitations the complex dynamics in stellar interiors that result in turbulent motions, mixing processes, and magnetic field generation, are …
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Quantification of the spatial and temporal evolution of stratified shear instabilities at high Reynolds number using quantitative acoustic scattering techniques
The spatial and temporal evolution of stratified shear instabilities is quantified in a highly stratified and energetic estuary. The measurements are made using high-resolution acoustic backscatter from an array composed of six calibrated broadband transducers connected to a six-channel …
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Quantification of the spatial and temporal evolution of stratified shear instabilities at high Reynolds number using quantitative acoustic scattering techniques
The spatial and temporal evolution of stratified shear instabilities is quantified in a highly stratified and energetic estuary. The measurements are made using high-resolution acoustic backscatter from an array composed of six calibrated broadband transducers connected to a six-channel …
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Linear and nonlinear dynamics in stratified shear flows
Stably stratified shear flows, in which a less dense layer of fluid lies above and moves counter to a more dense layer below, are ubiquitous in geophysical fluid dynamics. These are often found to be unstable if the non-dimensional Richardson number Ri, quantifying the strength of stratification to …
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Arabian Sea mixed layer deepening during the monsoon : observations and dynamics
… latent heat losses at the surface. Wind-driven shear instabilities at the base of the mixed layer, which entrain cooler and fresher water primarily produces the observed mixed layer cooling and deepening. Horizontal advection of cooler water within the mixed layer influences the local heat …
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Momentum and mass transport by coherent structures in a shallow vegetated shear flow
… vegetation and a high conveyance channel. A shear flow develops across this interface and its dynamics influences the exchange of mass and momentum between the vegetation and the channel. This thesis describes an experimental study in a shallow laboratory channel with 1/3 of its width filled …
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Magnetized models for the formation of the moon
… occurs during the collision phase as the planets shear against one another. In the post-impact, differentially rotating debris disk, magnetic winding grows field strengths linearly in time. Turbulence driven by the magnetorotational instability (MRI) is capable of growing field strengths …
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Formation and evolution of hypernova progenitors in massive binary systems
… due to convection, dynamical and secular shear instabilities, and gravity (buoyancy) waves.
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Effects of Compressibility and Variable-Density on the Instability Growth within Buoyancy-Driven Shear Layers
… on the instability growth within buoyancy-driven shear layers (BSL), which share characteristics with the canonical Rayleigh-Taylor (RT/RTI) and Kelvin-Helmholtz (KH/KHI) instabilities. The 2D simulations are performed in a periodic domain, with alternating columns of high and low density fluids …
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A high-order hybrid flow solver for the simulation of nonlinear internal waves in long complex domains
… As the ISW shoals, the resulting convective and shear instabilities and ISW-driven turbulence are investigated.
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Energetics and mixing in stratified turbulent flows
… large amplitude, it can break due to convective instabilities or shear instabilities. A fundamental understanding of the turbulent transition arising from these instabilities is useful for both interpreting observations and predicting 'hotspots' of turbulence in the field. Focusing solely on …
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A Study of Instability Mechanisms Driving Cloud Cavitation: Experimental Analysis Using New Advanced Velocimetry and Evaluation of Numerical Models
… shedding, challenging the conventional view that shear instabilities are secondary in macro-scale flows. The analysis revealed a coupled mechanism where shear-induced vortex roll-up initiates local collapse events, which subsequently generate the acoustic perturbations necessary to drive …
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Hydraulics and instabilities of quasi-geostrophic zonal flows
… only wave present is the Rossby wave modified by shear. While others (Armi 1989, Pratt 1989, Haynes et al.1993 and Woods 1993) have examined specific examples of shear flow "hydraulics", my goal was to find general criteria for the types of flows that may exhibit hydraulic behavior. In addition, a …
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Modelling turbulence and transport of buoyant material in the ocean surface mixed layer
… model the movement of buoyant particles. Shear instabilities drive turbulence which enhances mixing, and strongly buoyant particles are carried out of the front during the first inertial period, which segregates the particles and leaves a large void in the centre of the front. In contrast, …
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On convective penetration of a buoyant plume into a stably stratified layer
… examine the influence of large-scale vertical shear. We find that hydration is controlled by mixing which is modulated by sedimentation and directly influenced by convective intensity. Vertical shear enhances hydration by promoting small-scale mixing via internal wave breaking and shear …
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The Dynamics of Geophysical and Astrophysical Turbulence
… perturbations of the horizontal shear are always unstable in the limit of strong stratification and strong thermal diffusion, causing the flow to develop vertical layers, and hence vertical shear, in the velocity field, thereby allowing vertical shear instabilities to develop. The …
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Vertical Transport of Sediment from Muddy Buoyant River Plumes in the Presence of Different Modes of Interfacial Instabilities
… sedimentation are flocculation and interfacial instabilities. We experimentally measured the sediment fluxes from each of these processes using two sets of laboratory experiments that investigate two different modes of instability, one driven by sediment settling and one driven by fluid shear. …
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Satellite and lagrangian observations of mesoscale surface processes in the southwestern Atlantic Ocean
… occur in the study area. The importance of the shear instabilities in the oceanographic front between the BC and the BCC for the eddy generation and mixture processes is emphasised here. Comparing AVHRR and buoy data, empirical relationships are obtained for linking eddy sizes to their …
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Waves and turbulence in sustained stratified shear flows
… picture of these sustained stratified shear flows. We start by characterising the variety of observed behaviours, or flow regimes, as we vary the density difference between the two reservoirs, the angle of inclination of the duct with respect to the horizontal, the way the density …
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