Nonlinear evolution of a narrow stratified velocity‐shear layer

1996 ◽  
Vol 3 (4) ◽  
pp. 1259-1262 ◽  
Author(s):  
M. J. Keskinen
Keyword(s):  
Shear Layer ◽  
Nonlinear Evolution ◽  
Velocity Shear

scholarly journals Effects of velocity shear layer on detonation propagation in a supersonic expanding combustor

2021 ◽  
Vol 33 (10) ◽  
pp. 105110
Author(s):  
Jian Dai ◽  
Fei Xu ◽  
Xiaodong Cai ◽  
Yasser Mahmoudi
Keyword(s):  
Shear Layer ◽  
Velocity Shear ◽  
Detonation Propagation

Nonlinear dynamics of the elliptic instability

2010 ◽  
Vol 646 ◽  
pp. 471-480 ◽  
Author(s):  
NATHANAËL SCHAEFFER ◽  
STÉPHANE LE DIZÈS
Keyword(s):  
Nonlinear Dynamics ◽  
Numerical Simulations ◽  
Shear Layer ◽  
Rapid Growth ◽  
Vortex Core ◽  
Nonlinear Evolution ◽  
Core Size ◽  
Layer Formation ◽  
Vortex Loop ◽  
Weakly Nonlinear

In this paper, we analyse by numerical simulations the nonlinear dynamics of the elliptic instability in the configurations of a single strained vortex and a system of two counter-rotating vortices. We show that although a weakly nonlinear regime associated with a limit cycle is possible, the nonlinear evolution far from the instability threshold is, in general, much more catastrophic for the vortex. In both configurations, we put forward some evidence of a universal nonlinear transition involving shear layer formation and vortex loop ejection, leading to a strong alteration and attenuation of the vortex, and a rapid growth of the vortex core size.

Electrostatic and magnetic fluctuations in the proximity of the velocity shear layer in the TJ‐I tokamak

1992 ◽  
Vol 4 (12) ◽  
pp. 4007-4011 ◽  
Author(s):  
I. García‐Cortés ◽  
M. A. Pedrosa ◽  
C. Hidalgo ◽  
B. Brañas ◽  
T. Estrada ◽  
...  
Keyword(s):  
Shear Layer ◽  
Velocity Shear ◽  
Magnetic Fluctuations

Velocity shear layer measurements by reflectometry in TJ-II plasmas

2006 ◽  
Vol 46 (9) ◽  
pp. S792-S798 ◽  
Author(s):  
T Estrada ◽  
E Blanco ◽  
L Cupido ◽  
M.E Manso ◽  
J Sánchez
Keyword(s):  
Shear Layer ◽  
Velocity Shear

Linear and nonlinear barotropic instability of geostrophic shear layers

1991 ◽  
Vol 224 ◽  
pp. 49-76 ◽  
Author(s):  
L. J. Pratt ◽  
J. Pedlosky
Keyword(s):  
Shear Layer ◽  
Nonlinear Evolution ◽  
Shear Layers ◽  
Linear Instability ◽  
Barotropic Instability ◽  
Reasonable Estimate ◽  
Weakly Nonlinear ◽  
Strongly Nonlinear ◽  
Weakly Nonlinear Theory ◽  
Geostrophic Shear

The linear, weakly nonlinear and strongly nonlinear evolution of unstable waves in a geostrophic shear layer is examined. In all cases, the growth of initially small-amplitude waves in the periodic domain causes the shear layer to break up into a series of eddies or pools. Pooling tends to be associated with waves having a significant varicose structure. Although the linear instability sets the scale for the pooling, the wave growth and evolution at moderate and large amplitudes is due entirely to nonlinear dynamics. Weakly nonlinear theory provides a catastrophic time ts at which the wave amplitude is predicted to become infinite. This time gives a reasonable estimate of the time observed for pools to detach in numerical experiments with marginally unstable and rapidly growing waves.

Drift-wave transport in the velocity shear layer

2016 ◽  
Vol 23 (7) ◽  
pp. 072504
Author(s):  
K. C. Rosalem ◽  
M. Roberto ◽  
I. L. Caldas
Keyword(s):  
Shear Layer ◽  
Velocity Shear ◽  
Drift Wave ◽  
Wave Transport

scholarly journals Existence, stability and formation of baroclinic tripoles in quasi-geostrophic flows

2015 ◽  
Vol 785 ◽  
pp. 1-30 ◽  
Author(s):  
Jean N. Reinaud ◽  
Xavier Carton
Keyword(s):  
Nonlinear Evolution ◽  
Baroclinic Instability ◽  
Steady States ◽  
Point Vortices ◽  
Velocity Shear ◽  
Vertical Shear ◽  
Finite Area ◽  
Geostrophic Flows ◽  
Vertically Aligned ◽  
Baroclinic Vortices

Hetons are baroclinic vortices able to transport tracers or species, which have been observed at sea. This paper studies the offset collision of two identical hetons, often resulting in the formation of a baroclinic tripole, in a continuously stratified quasi-geostrophic model. This process is of interest since it (temporarily or definitely) stops the transport of tracers contained in the hetons. First, the structure, stationarity and nonlinear stability of baroclinic tripoles composed of an upper core and two lower (symmetric) satellites are studied analytically for point vortices and numerically for finite-area vortices. The condition for stationarity of the point vortices is obtained and it is proven that the baroclinic point tripoles are neutral. Finite-volume stationary tripoles exist with marginal states having very elongated (figure-of-eight shaped) upper cores. In the case of vertically distant upper and lower cores, the latter can nearly join near the centre of the plane. These steady states are compared with their two-layer counterparts. Then, the nonlinear evolution of the steady states shows when they are often neutral (showing an oscillatory evolution); when they are unstable, they can either split into two hetons (by breaking of the upper core) or form a single heton (by merger of the lower satellites). These evolutions reflect the linearly unstable modes which can grow on the vorticity poles. Very tall tripoles can break up vertically due to the vertical shear mutually induced by the poles. Finally, the formation of such baroclinic tripoles from the offset collision of two identical hetons is investigated numerically. This formation occurs for hetons offset by less than the internal separation between their poles. The velocity shear during the interaction can lead to substantial filamentation by the upper core, thus forming small upper satellites, vertically aligned with the lower ones. Finally, in the case of close and flat poles, this shear (or the baroclinic instability of the tripole) can be strong enough that the formed baroclinic tripole is short-lived and that hetons eventually emerge from the collision and drift away.

Electrostatic Turbulence and Transport in the Velocity Shear Layer of a Reversed Field Pinch Plasma

1998 ◽  
Vol 80 (19) ◽  
pp. 4185-4188 ◽  
Author(s):  
V. Antoni ◽  
R. Cavazzana ◽  
D. Desideri ◽  
E. Martines ◽  
G. Serianni ◽  
...  
Keyword(s):  
Shear Layer ◽  
Velocity Shear ◽  
Reversed Field Pinch ◽  
Pinch Plasma ◽  
Reversed Field

Effect of Multi-Modal Forcing on Thermal Transport in a Co-Axial Combustor Geometry

2001 ◽  
Author(s):  
P. R. Chandra ◽  
Chun L. Lau ◽  
S. Acharya
Keyword(s):  
Shear Layer ◽  
Coherent Structures ◽  
Near Field ◽  
Single Mode ◽  
Spreading Rate ◽  
Open Loop ◽  
Velocity Shear ◽  
Scalar Mixing ◽  
Jet Streams ◽  
Loop Control

Abstract This paper investigates open-loop control of the mixing between an inner stream and an outer stream in a coaxial combustor geometry. The inner and outer air streams enter the combustor geometry at different temperatures and mimic a gaseous fuel and combustion air stream respectively. Of specific interest in this study is the behavior of the coherent structures in the coaxial jet streams, and the manipulation of these coherent structures with controlled perturbation to enhance jet-spreading and scalar-mixing. The spectra of the unforced flow reveal the presence of a dominant coherent mode at 100 Hz (identified as the fundamental mode fo), as well as 150 Hz (3 fo/2) and 300 Hz (3 fo). Single-mode forcing of both the inner-jet and the outer-jet at 100 Hz, 150 Hz, 300 Hz, and 1 kHz is explored, and attention is focused on the spreading of the inner-jet shear layer and the outer-jet shear layer. It is observed that the 300 Hz mode shows the greatest enhancement in the spreading rate of the velocity shear-layer in the near field (x/D < 1), while downstream of x/D = 1, the 100 Hz appears to show the most significant effect. Scalar mixing is also significantly enhanced, with the 300 Hz forcing showing the largest enhancement. Dual-mode forcing is also investigated with 100 Hz inner-jet, 300 Hz outer-jet forcing and 300 Hz inner-jet, 100 Hz outer-jet forcing. The 100 Hz inner-jet, 300 Hz outer-jet forcing is shown to lead to greater enhancements in scalar mixing man all other cases considered.

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