Interfacial solitons propagating through a background shear current

2020 ◽  
Vol 32 (10) ◽  
pp. 106603
Author(s):  
Giovanni la Forgia ◽  
Giampiero Sciortino
Keyword(s):  
Shear Current ◽  
Background Shear

scholarly journals The evolution of mode-2 internal solitary waves modulated by background shear currents

2018 ◽  
Vol 25 (2) ◽  
pp. 441-455 ◽  
Author(s):  
Peiwen Zhang ◽  
Zhenhua Xu ◽  
Qun Li ◽  
Baoshu Yin ◽  
Yijun Hou ◽  
...  
Keyword(s):  
Wave Packet ◽  
Shear Layer ◽  
Solitary Waves ◽  
Average Rate ◽  
Propagation Distance ◽  
Internal Solitary Waves ◽  
Long Wave ◽  
Shear Current ◽  
Mode 2 ◽  
Background Shear

Abstract. The evolution of mode-2 internal solitary waves (ISWs) modulated by background shear currents was investigated numerically. The mode-2 ISW was generated by the “lock-release” method, and the background shear current was initialized after the mode-2 ISW became stable. Five sets of experiments were conducted to assess the sensitivity of the modulation process to the direction, polarity, magnitude, shear layer thickness and offset extent of the background shear current. Three distinctly different shear-induced waves were identified as a forward-propagating long wave, oscillating tail and amplitude-modulated wave packet in the presence of a shear current. The amplitudes of the forward-propagating long wave and the amplitude-modulated wave packet are proportional to the magnitude of the shear but inversely proportional to the thickness of the shear layer, as well as the energy loss of the mode-2 ISW during modulation. The oscillating tail and amplitude-modulated wave packet show symmetric variation when the background shear current is offset upward or downward, while the forward-propagating long wave was insensitive to it. For comparison, one control experiment was configured according to the observations of Shroyer et al. (2010); in the first 30 periods, ∼ 36 % of total energy was lost at an average rate of 9 W m−1 in the presence of the shear current; it would deplete the energy of initial mode-2 ISWs in ∼ 4.5 h, corresponding to a propagation distance of ∼ 5 km, which is consistent with in situ data.

Resonant wave interactions in a stratified shear flow

1988 ◽  
Vol 190 ◽  
pp. 357-374 ◽  
Author(s):  
R. Grimshaw
Keyword(s):  
Shear Flow ◽  
Gravity Waves ◽  
Critical Level ◽  
Internal Gravity Waves ◽  
Wave Interactions ◽  
Resonant Wave ◽  
Resonant Interactions ◽  
Stratified Shear Flow ◽  
Weak Resonance ◽  
Background Shear

Resonant interactions between triads of internal gravity waves propagating in a shear flow are considered for the case when the stratification and the background shear flow vary slowly with respect to typical wavelengths. If ωn, kn(n = 1, 2, 3) are the local frequencies and wavenumbers respectively then the resonance conditions are that ω1 + ω2 + ω3 = 0 and k1 + k2 + k3 = 0. If the medium is only weakly inhomogeneous, then there is a strong resonance and to leading order the resonance conditions are satisfied globally. The equations governing the wave amplitudes are then well known, and have been extensively discussed in the literature. However, if the medium is strongly inhomogeneous, then there is a weak resonance and the resonance conditions can only be satisfied locally on certain space-time resonance surfaces. The equations governing the wave amplitudes in this case are derived, and discussed briefly. Then the results are applied to a study of the hierarchy of wave interactions which can occur near a critical level, with the aim of determining to what extent a critical layer can reflect wave energy.

scholarly journals Angular Momentum Transport and Dynamo Effect in Kepler Disks

2001 ◽  
Vol 200 ◽  
pp. 410-414
Author(s):  
Günther Rüdiger ◽  
Udo Ziegler
Keyword(s):  
Angular Momentum ◽  
Accretion Disks ◽  
Large Scale ◽  
Spherical Model ◽  
Momentum Transport ◽  
Rotational Instability ◽  
Jet Formation ◽  
Angular Momentum Transport ◽  
Dynamo Effect ◽  
Background Shear

Properties have been demonstrated of the magneto-rotational instability for two different applications, i.e. for a global spherical model and a box simulation with Keplerian background shear flow. In both nonlinear cases a dynamo operates with a negative (positive) α-effect in the northern (southern) disk hemisphere and in both cases the angular momentum transport is outwards. Keplerian accretion disks should therefore exhibit large-scale magnetic fields with a dipolar geometry of the poloidal components favoring jet formation.

On the near-wall characteristics of acceleration in turbulence

2010 ◽  
Vol 659 ◽  
pp. 405-419 ◽  
Author(s):  
K. YEO ◽  
B.-G. KIM ◽  
C. LEE
Keyword(s):  
Turbulent Flows ◽  
Streamwise Vortex ◽  
Reynolds Numbers ◽  
Viscous Sublayer ◽  
Centripetal Acceleration ◽  
Vortical Structures ◽  
Turbulent Channel Flows ◽  
Background Shear ◽  
Kolmogorov Constant ◽  
Near Wall

The behaviour of fluid-particle acceleration in near-wall turbulent flows is investigated in numerically simulated turbulent channel flows at low to moderate Reynolds numbers, Reτ = 180~600). The acceleration is decomposed into pressure-gradient (irrotational) and viscous contributions (solenoidal acceleration) and the statistics of each component are analysed. In near-wall turbulent flows, the probability density function of acceleration is strongly dependent on the distance from the wall. Unexpectedly, the intermittency of acceleration is strongest in the viscous sublayer, where the acceleration flatness factor of O(100) is observed. It is shown that the centripetal acceleration around coherent vortical structures is an important source of the acceleration intermittency. We found sheet-like structures of strong solenoidal accelerations near the wall, which are associated with the background shear modified by the interaction between a streamwise vortex and the wall. We found that the acceleration Kolmogorov constant is a linear function of y+ in the log layer. The Reynolds number dependence of the acceleration statistics is investigated.

Disruption of the bottom log layer in large-eddy simulations of full-depth Langmuir circulation

2012 ◽  
Vol 699 ◽  
pp. 79-93 ◽  
Author(s):  
A. E. Tejada-Martínez ◽  
C. E. Grosch ◽  
N. Sinha ◽  
C. Akan ◽  
G. Martinat
Keyword(s):  
Gravity Waves ◽  
Large Eddy Simulations ◽  
Stokes Drift ◽  
Navier Stokes ◽  
Wake Region ◽  
Langmuir Circulation ◽  
Mean Velocity ◽  
Wave Forcing ◽  
Large Eddy ◽  
Shear Current

AbstractWe report on disruption of the log layer in the resolved bottom boundary layer in large-eddy simulations (LES) of full-depth Langmuir circulation (LC) in a wind-driven shear current in neutrally-stratified shallow water. LC consists of parallel counter-rotating vortices that are aligned roughly in the direction of the wind and are generated by the interaction of the wind-driven shear with the Stokes drift velocity induced by surface gravity waves. The disruption is analysed in terms of mean velocity, budgets of turbulent kinetic energy (TKE) and budgets of TKE components. For example, in terms of mean velocity, the mixing due to LC induces a large wake region eroding the classical log-law profile within the range $90\lt { x}_{3}^{+ } \lt 200$. The dependence of this disruption on wind and wave forcing conditions is investigated. Results indicate that the amount of disruption is primarily determined by the wavelength of the surface waves generating LC. These results have important implications for turbulence parameterizations for Reynolds-averaged Navier–Stokes simulations of the coastal ocean.

scholarly journals Simulating background shear flow in local gyrokinetic simulations

2019 ◽  
Vol 61 (5) ◽  
pp. 055006 ◽  
Author(s):  
B F McMillan ◽  
J Ball ◽  
S Brunner
Keyword(s):  
Shear Flow ◽  
Background Shear ◽  
Gyrokinetic Simulations

scholarly journals Properties of a Simulated Convective Boundary Layer in an Idealized Supercell Thunderstorm Environment

2014 ◽  
Vol 142 (11) ◽  
pp. 3955-3976 ◽  
Author(s):  
Christopher J. Nowotarski ◽  
Paul M. Markowski ◽  
Yvette P. Richardson ◽  
George H. Bryan
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Convective Available Potential Energy ◽  
Vertical Wind Shear ◽  
Surface Fluxes ◽  
Convective Boundary ◽  
Eddy Simulation ◽  
Sensitivity Tests ◽  
Supercell Thunderstorms ◽  
Background Shear

Abstract Nearly all previous numerical simulations of supercell thunderstorms have neglected surface fluxes of heat, moisture, and momentum. This choice precludes horizontal inhomogeneities associated with dry boundary layer convection in the near-storm environment. As part of a broader study on how mature supercell thunderstorms are affected by a convective boundary layer (CBL) with quasi-two-dimensional features (i.e., boundary layer rolls), this paper documents the methods used to develop a realistic CBL in an idealized environment supportive of supercells. The evolution and characteristics of the modeled CBL, including the horizontal variability of thermodynamic and kinematic quantities known to affect supercell evolution, are presented. The simulated rolls result in periodic bands of perturbations in temperature, moisture, convective available potential energy (CAPE), vertical wind shear, and storm-relative helicity (SRH). Vertical vorticity is shown to arise within the boundary layer through the tilting of ambient horizontal vorticity associated with the background shear by vertical velocity perturbations in the turbulent CBL. Sensitivity tests suggest that 200-m horizontal grid spacing is adequate to represent rolls using a large-eddy simulation (LES) approach.

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