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Showing 1 to 20 of 73 for “"Kelvin-Helmholtz"”.
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Mesospheric Kelvin-Helmholtz instability
This work examines the Kelvin-Helmholtz instability, comparing features extracted from a numerical fully nonlinear model to radar and rocket measurements of free electron density and neutral motions in the mesosphere. Previous models of shear instability are reviewed, and relevant mesospheric …
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Kelvin-Helmholtz Instability in Magnetized Plasma
… in many systems in the universe, are generally Kelvin-Helmholtz unstable. If the medium is ionized, the presence of a magnetic field can influence the evolution of this instability; depending on its strength and orientation, the field has either a stabilizing or destabilizing effect. We …
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Kelvin-Helmholtz instability in aluminium reduction cells
… between the layers, which gives rise to a Kelvin-Helmholtz instability, and the study of this effect is the subject of the thesis. The role of the basic steady flow is focused in this analysis, while most previous MHD analyses neglect it and emphasise on the interaction between the …
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Multifluid Kelvin-Helmholtz instability in weakly ionised astrophysical plasmas
… on fluid instabilities, in particular the Kelvin-Helmholtz (KH) instability. The KH instability could, for example, play a role in the momentum transfer between the bowshock of a protostellar jet and its surrounding molecular cloud. In particular, changes to the development of the KH …
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Numerical analysis and visualization of the ionospheric Kelvin-Helmholtz instability
… irregularities; namely the evolution of the Kelvin-Helmholtz instability (KHI) is studied. The simulation model consists of two-dimensional, electrostatic, nonlinear, and time dependent fluid equations that describe the KHI evolution. Spectral and pseudospectral methods are used to solve the …
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Identifying Signatures of Plasma Waves and Reconnection Associated with Kelvin-Helmholtz Activity
… Recent work has shown that reconnection in Kelvin-Helmholtz vortices can transport plasma into the magnetosphere. Previous studies have also shown that mode conversion at the magnetopause can generate kinetic Alfvén wave (KAW) activity. Both magnetic reconnection and plasma wave activity can …
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MMS Observations of the Kelvin-Helmholtz Instability and Associated Ion Scale Waves
… must be at work. One potential process is the Kelvin-Helmholtz instability (KHI). The KHI is a convective instability which operates at the fluid scale in plasmas, but is capable of driving secondary process at smaller scales. Previous work has shown evidence of magnetic reconnection, various …
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Analysis of Kelvin-Helmholtz Instabilities Developing from Oblique Shock Interaction with a Heavy Gas Column
… vortices, physically indistinguishable from Kelvin-Helmholtz instabilities (KHI). Certain characteristics of the KHI, such as initial instability growth rate and wavelength (lambda), depend on several factors including the Mach number of the shock wave, the shock tube angle of inclination …
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The Numerical Simulation of Thunderstorm Outflow Dynamics (Gust Front, Kelvin-Helmholtz Instability, Wind Shear, Microbursts)
Two high-resolution, two-dimensional numerical models are developed and used to investigate the dynamics of thunderstorm outflows. The first model employs the set of unapproximated, inviscid, fully compressible hydrodynamical equations, while the second, more economical model is based on a …
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Hydrodynamic stability of liquid films adjacent to incompressible gas streams including effects of interface mass transfer
… has nearly the same speed of propagation as a Kelvin-Helmholtz wave for small wave numbers and hence it was called the modified Kelvin-Helmholtz mode. The variation with respect to the disturbance wave number, of the first five slow moving modes and a representative fast moving mode, is …
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Modeling and Large Scale Simulations of Thermohaline and Particulate Density Currents
… wide range of scales. Front spreading velocity, Kelvin-Helmholtz vortex dynamics, lobe and cleft formation and evolution, flow patterns, and bed shear stress patterns, are visualized and explored in detail. The simulation results are compared throughout the work to previously published …
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Nonlinear effects on interfacial wave growth into slug flow
… wave disturbances on the interface: the classic Kelvin-Helmholtz instability or shear induced instability. These instability mechanisms, which affect the initial growth of the disturbances on the interface, are well understood; however, the subsequent nonlinear evolution and the effects of wave …
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Turbulent flows over canopies
… turbulence and from the flow arising from the Kelvin--Helmholtz-like, mixing-layer instability typically reported over dense canopies. For the present canopies, with spacings $s^+ \approx 3$--$50$, the background turbulence is essentially precluded from penetrating within the canopy. As the …
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Data Analysis of an Unsteady Cavitating Flow on a Venturi-type Profile
… to slow-varying drift flow, cloud-shedding, and Kelvin-Helmholtz (KH) instability for a fixed inlet flow condition. The high coherence measure obtained from the instabilities suggests a transfer of energy from the largest scales, fluctuating mean flow, to the smaller scales such as cloud …
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Numerical detection of complex singularities in two and three dimensions
… role in interfacial fluid dynamics such as Kelvin-Helmholtz instability, Rayleigh-Taylor instability, and Hele-Shaw flow. In this thesis, we present a new method for the numerical analysis of complex singularities in solutions to partial differential equations. In the method, we analyze the …
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Fully nonlinear interfacial waves in a bounded two-fluid system
… phase can be different, thus giving rise to the Kelvin-Helmholtz instability. Our objective is to study the competing effects of the Kelvin-Helmholtz instability coupled with a stably or unstably stratified fluid system (Rayleigh-Taylor instability) when surface tension is present to regularize …
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Trace finite element method for material surface flows
… numerical examples which include simulation of Kelvin--Helmholtz instability at different Reynolds numbers on a sphere and torus, as well as tangential flow induced by inextensible radial deformations of a surface.
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Linear and nonlinear dynamics in stratified shear flows
… It is found that while the classical Kelvin-Helmholtz instability does indeed exhibit subcriticality, nonlinear steady states are found only just above Ri = 1/4. Chapter 3 investigates in detail a hitherto unknown linear instability, which was discovered in chapter 2. Behaving …
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Visualization of the Vortex Lattice Dynamics in Superfluid Helium
… distinct Stewartson layer boundaries, possible Kelvin-Helmholtz instabilities, and the formation and propagation of superfluid collective vortex eddies. We show that the angular velocity is a function of radius and may be driven by the geometry of the isolation cell. We also document the …
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Quantitative Characterization of Billowed Structures Along the Margins of Basaltic Intrusions to Determine Process and Timing of Formation: Case Studies from Big Bend National Park, Texas and 71 Gulch, Idaho
… to cooling of intruding magma while experiencing Kelvin-Helmholtz instabilities. Aligned plagioclase laths and stretched vesicles along margins are evidence that the formation of billowed structures occurred while the margins were fluid, deformable, and flowing. Linear billow crests in BBNP were …
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