scholarly journals The effects of ambient stratification on the crow instability and subsequent vortex reconnection

1999 ◽  
Vol 7 ◽  
pp. 151-160
Author(s):  
J. F. Garten ◽  
J. Werne ◽  
D. C. Fritts ◽  
S. Arendt
Keyword(s):  
Vortex Reconnection ◽  
Crow Instability

Direct numerical simulations of the Crow instability and subsequent vortex reconnection in a stratified fluid

2001 ◽  
Vol 426 ◽  
pp. 1-45 ◽  
Author(s):  
J. F. GARTEN ◽  
J. WERNE ◽  
D. C. FRITTS ◽  
S. ARENDT
Keyword(s):  
Growth Rate ◽  
Numerical Model ◽  
Time Scale ◽  
Three Dimensional ◽  
Vortex Pair ◽  
Direct Numerical Simulations ◽  
Reversal Effect ◽  
Vortex Reconnection ◽  
Vertically Propagating ◽  
Crow Instability

The evolution of a vertically propagating three-dimensional vortex pair in ambient stratification is studied with a three-dimensional numerical model. We consider a range of Reynolds (Re) and Froude (Fr) numbers, and initialize the vortex pair in a configuration that promotes growth of the Crow instability (Crow 1970). The growth rate of the instability is Re dependent, and we present a method for extending Crow's model to predict this dependence. We also find that relatively strong ambient stratification (Fr [les ] 2) further alters the growth of the instability via advection by baroclinically produced vorticity. For all of our cases with Fr [ges ] 1 (including our unstratified cases where Fr → ∞), the instability leads to vortex reconnection and formation of a vortex ring. A larger Re delays the commencement of the reconnection, but it proceeds more rapidly once it does commence. We compute a reconnection time scale (tR), and find that tR ∼ 1/Re, in agreement with a model formulated by Shelley et al. (1993). We also discuss a deformative/diffusive effect (related to yet distinct from the curvature reversal effect discussed by Melander & Hussain 1989) which prevents complete reconnection. Ambient stratification (in the range Fr [ges ] 1) accelerates the reconnection and reduces tR by an amount roughly proportional to 1/Fr. For some Fr, stratification effects overwhelm the deformative effect, and complete reconnection results.

Large eddy simulation of aircraft wake vortices within homogeneous turbulence - Crow instability

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 292-300 ◽  
Author(s):  
Jongil Han ◽  
Yuh-Lang Lin ◽  
David G. Schowalter ◽  
S. P. Arya ◽  
Fred H. Proctor
Keyword(s):  
Large Eddy Simulation ◽  
Homogeneous Turbulence ◽  
Wake Vortices ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Aircraft Wake ◽  
Crow Instability

scholarly journals On Lagrangian and vortex-surface fields for flows with Taylor–Green and Kida–Pelz initial conditions

2010 ◽  
Vol 661 ◽  
pp. 446-481 ◽  
Author(s):  
YUE YANG ◽  
D. I. PULLIN
Keyword(s):  
Incompressible Flows ◽  
Initial Conditions ◽  
Scalar Fields ◽  
Local Geometry ◽  
Optimization Approach ◽  
Vortex Reconnection ◽  
Barotropic Flow ◽  
Lagrangian Surfaces ◽  
Definition Of ◽  
Surface Fields

For a strictly inviscid barotropic flow with conservative body forces, the Helmholtz vorticity theorem shows that material or Lagrangian surfaces which are vortex surfaces at time t = 0 remain so for t > 0. In this study, a systematic methodology is developed for constructing smooth scalar fields φ(x, y, z, t = 0) for Taylor–Green and Kida–Pelz velocity fields, which, at t = 0, satisfy ω·∇φ = 0. We refer to such fields as vortex-surface fields. Then, for some constant C, iso-surfaces φ = C define vortex surfaces. It is shown that, given the vorticity, our definition of a vortex-surface field admits non-uniqueness, and this is presently resolved numerically using an optimization approach. Additionally, relations between vortex-surface fields and the classical Clebsch representation are discussed for flows with zero helicity. Equations describing the evolution of vortex-surface fields are then obtained for both inviscid and viscous incompressible flows. Both uniqueness and the distinction separating the evolution of vortex-surface fields and Lagrangian fields are discussed. By tracking φ as a Lagrangian field in slightly viscous flows, we show that the well-defined evolution of Lagrangian surfaces that are initially vortex surfaces can be a good approximation to vortex surfaces at later times prior to vortex reconnection. In the evolution of such Lagrangian fields, we observe that initially blob-like vortex surfaces are progressively stretched to sheet-like shapes so that neighbouring portions approach each other, with subsequent rolling up of structures near the interface, which reveals more information on dynamics than the iso-surfaces of vorticity magnitude. The non-local geometry in the evolution is quantified by two differential geometry properties. Rolled-up local shapes are found in the Lagrangian structures that were initially vortex surfaces close to the time of vortex reconnection. It is hypothesized that this is related to the formation of the very high vorticity regions.

scholarly journals Crow instability effects on the exhaust plume mixing and condensation

1999 ◽  
Vol 7 ◽  
pp. 66-79 ◽  
Author(s):  
S. Brunet ◽  
F. Garnier ◽  
P. Sagaut
Keyword(s):  
Exhaust Plume ◽  
Crow Instability

Importance of Antisymmetric Modes of the Crow Instability

AIAA Journal ◽  
2017 ◽  
Vol 55 (7) ◽  
pp. 2123-2128 ◽  
Author(s):  
Zhongquan Charlie Zheng ◽  
Jay C. Hardin
Keyword(s):  
Crow Instability

scholarly journals Numerical study of the vortex breakdown and vortex reconnection in the flow path of high-pressure water turbine

2021 ◽  
Vol 2088 (1) ◽  
pp. 012040
Author(s):  
A V Sentyabov ◽  
D V Platonov ◽  
A V Minakov ◽  
A S Lobasov
Keyword(s):  
Vortex Core ◽  
Vortex Breakdown ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Hydraulic Turbine ◽  
Sliding Mesh ◽  
Precessing Vortex Core ◽  
Vortex Reconnection ◽  
Water Turbine ◽  
Pressure Water

Abstract The paper presents a study of the instability of the precessing vortex core in the model of the draft tube of a hydraulic turbine. The study was carried out using numerical modeling using various approaches: URANS, RSM, LES. The best agreement with the experimental data was shown by the RSM and LES methods with the modelling of the runner rotation by the sliding mesh method. In the regime under consideration, the precessing vortex rope is subject to instability, which leads to reconnection of its turns and the formation of an isolated vortex ring. Reconnection of the vortex core leads to aperiodic and intense pressure fluctuations recorded on the diffuser wall.

scholarly journals Vortex reconnections in classical and quantum fluids

SeMA Journal ◽  
2021 ◽  
Author(s):  
Alberto Enciso ◽  
Daniel Peralta-Salas
Keyword(s):  
Stokes Equations ◽  
Quantum Fluids ◽  
Navier Stokes ◽  
Pitaevskii Equation ◽  
Global Approximation ◽  
Rigorous Results ◽  
Navier Stokes Equations ◽  
Localization Principle ◽  
Global Smooth Solutions ◽  
Vortex Reconnection

AbstractWe review recent rigorous results on the phenomenon of vortex reconnection in classical and quantum fluids. In the context of the Navier–Stokes equations in $$\mathbb {T}^3$$ T 3 we show the existence of global smooth solutions that exhibit creation and destruction of vortex lines of arbitrarily complicated topologies. Concerning quantum fluids, we prove that for any initial and final configurations of quantum vortices, and any way of transforming one into the other, there is an initial condition whose associated solution to the Gross–Pitaevskii equation realizes this specific vortex reconnection scenario. Key to prove these results is an inverse localization principle for Beltrami fields and a global approximation theorem for the linear Schrödinger equation.

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