Accurate numerical simulations of vortex flows II: Interaction of swirling vortex rings

2011 ◽  
Vol 41 (1) ◽  
pp. 110-118 ◽  
Author(s):  
W. Kollmann
Keyword(s):  
Numerical Simulations ◽  
Vortex Rings ◽  
Vortex Flows ◽  
Swirling Vortex

Vortex rings impinging on walls: axisymmetric and three-dimensional simulations

1993 ◽  
Vol 256 ◽  
pp. 615-646 ◽  
Author(s):  
Paolo Orlandi ◽  
Roberto Verzicco
Keyword(s):  
Numerical Simulations ◽  
Strain Tensor ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Vortex Rings ◽  
Compression Phase ◽  
Vortex Pairing ◽  
The Impact ◽  
Good Agreement ◽  
Three Dimensional Simulations

Accurate numerical simulations of vortex rings impinging on flat boundaries revealed the same features observed in experiments. The results for the impact with a free-slip wall compared very well with previous numerical simulations that used spectral methods, and were also in qualitative agreement with experiments. The present simulation is mainly devoted to studying the more realistic case of rings interacting with a no-slip wall, experimentally studied by Walker et al. (1987). All the Reynolds numbers studied showed a very good agreement between experiments and simulations, and, at Rev > 1000 the ejection of a new ring from the wall was seen. Axisymmetric simulations demonstrated that vortex pairing is the physical mechanism producing the ejection of the new ring. Three-dimensional simulations were also performed to investigate the effects of azimuthal instabilities. These simulations have confirmed that high-wavenumber instabilities originate in the compression phase of the secondary ring within the primary one. The large instability of the secondary ring has been explained by analysis of the rate-of-strain tensor and vorticity alignment. The differences between passive scalars and the vorticity field have been also investigated.

scholarly journals Steady axisymmetric vortex flows with swirl and shear

2008 ◽  
Vol 613 ◽  
pp. 395-410 ◽  
Author(s):  
ALAN R. ELCRAT ◽  
BENGT FORNBERG ◽  
KENNETH G. MILLER
Keyword(s):  
Multiple Solutions ◽  
Iterative Procedure ◽  
General Procedure ◽  
Inviscid Flow ◽  
Initial Guess ◽  
Vortex Rings ◽  
Vortex Flows ◽  
Axisymmetric Vortex

A general procedure is presented for computing axisymmetric swirling vortices which are steady with respect to an inviscid flow that is either uniform at infinity or includes shear. We consider cases both with and without a spherical obstacle. Choices of numerical parameters are given which yield vortex rings with swirl, attached vortices with swirl analogous to spherical vortices found by Moffatt, tubes of vorticity extending to infinity and Beltrami flows. When there is a spherical obstacle we have found multiple solutions for each set of parameters. Flows are found by numerically solving the Bragg–Hawthorne equation using a non-Newton-based iterative procedure which is robust in its dependence on an initial guess.

scholarly journals The Formation and Evolution of Turbulent Swirling Vortex Rings Generated by Axial Swirlers

2019 ◽  
Vol 104 (4) ◽  
pp. 795-816 ◽  
Author(s):  
Chuangxin He ◽  
Lian Gan ◽  
Yingzheng Liu
Keyword(s):  
Propagation Velocity ◽  
Early Stage ◽  
Axial Direction ◽  
Vortex Rings ◽  
Eddy Simulation ◽  
Axis Parallel ◽  
3D Printed ◽  
Formation Number ◽  
Formation And Evolution ◽  
Swirling Vortex

AbstractThe present work investigates the formation process and early stage evolution of turbulent swirling vortex rings, by using planar Particle Image Velocimetry (PIV) and Large Eddy Simulation (LES). Vortex rings are produced in a piston-nozzle arrangement with swirl generated by 3D-printed axial swirlers in experiments. Idealised solid-body rotation is applied in LES to evaluate the effect of nozzle exit velocity profile in experiments. The Reynolds number (Re) based on the nozzle diameter D and the slug velocity U0 in the nozzle is 20,000. The swirl number S generated ranges from 0 (zero-swirl vortex ring) and 1.1, covering the two critical swirl numbers previously identified in a swirling jet. Both PIV and LES results show that the formation number F decreases linearly as S increases, with the maximum F ≈ 2.6 at S = 0 (produced by the swirler with straight vanes) and minimum F = 1.9 at S = 1.1. The corresponding maximum attainable circulation in the nozzle axis parallel plane also diminishes with increasing S. Evolution of compact rings produced by a stroke ratio L/D = 1.5 reveals that circulation decay rate is largely proportional to S. The trajectory of the vortex core in the axial direction, hence the ring axial propagation velocity, decreases as S, while that in the radial direction and the radial propagation velocity, increase with S. An empirical scaling function is proposed to scale these variables.

The linear stability of swirling vortex rings

2016 ◽  
Vol 28 (11) ◽  
pp. 114106 ◽  
Author(s):  
C. Gargan-Shingles ◽  
M. Rudman ◽  
K. Ryan
Keyword(s):  
Linear Stability ◽  
Vortex Rings ◽  
Swirling Vortex

scholarly journals Direct numerical simulations of vortex rings at ReΓ = 7500

2007 ◽  
Vol 581 ◽  
pp. 495-505 ◽  
Author(s):  
MICHAEL BERGDORF ◽  
PETROS KOUMOUTSAKOS ◽  
ANTHONY LEONARD
Keyword(s):  
Numerical Simulations ◽  
Vortex Dynamics ◽  
Direct Numerical Simulations ◽  
Online Version ◽  
Vortex Rings ◽  
Vortex Wake ◽  
Nonlinear Stage ◽  
Dye Visualization ◽  
Vorticity Dynamics ◽  
Experimental Works

We present direct numerical simulations of the turbulent decay of vortex rings with ReΓ = 7500. We analyse the vortex dynamics during the nonlinear stage of the instability along with the structure of the vortex wake during the turbulent stage. These simulations enable the quantification of vorticity dynamics and their correlation with structures from dye visualization and the observations of circulation decay that have been reported in related experimental works. Movies are available with the online version of the paper.

Circulation of Vortex Rings Formed From Tube and Orifice Openings

2006 ◽  
Author(s):  
Paul S. Krueger
Keyword(s):  
Reynolds Number ◽  
Numerical Simulations ◽  
Fold Increase ◽  
Numerical Results ◽  
Vortex Rings ◽  
Exit Plane ◽  
Slug Model ◽  
Vorticity Flux ◽  
Tube Geometry ◽  
Recent Extension

Two common configurations for generating vortex rings via jet pulses are the tube and orifice geometries. The orifice geometry forces the flow to contract as it approaches the jet exit plane, which can strongly affect vorticity flux and the circulation of the resulting ring. The author’s recent extension of the traditional slug model for vortex ring circulation (called the “pressure corrected” or PC model) accounts for the geometric differences between the tube and orifice cases, but model validation for the orifice geometry has been limited due to the lack of data for this configuration. The present study compares process of circulation generation by tube and orifice geometries using numerical simulations of finite duration jets from tube and orifice openings. Total jet slug length-to-diameter ratios (L/D) in the range of 0.5 to 3.5 and a jet Reynolds number of 2000 are considered. The numerical results confirm the underlying assumptions of the PC model. The model results for the tube geometry are within 14% of the numerical results. Incorporating the scaling of ring velocity with ejected jet length (X/D) obtained from the present numerical results improves the predictions for the orifice case, giving accuracy to within 20%. The overall geometry effect appears as a two-fold increase in circulation for the orifice case over the tube case at the same L/D.

Vortex Ring Formation on Drop Coalescence With Underlying Liquid

2013 ◽  
Author(s):  
Bahni Ray ◽  
Gautam Biswas ◽  
Ashutosh Sharma
Keyword(s):  
Numerical Simulations ◽  
Vortex Ring ◽  
Level Set ◽  
Flat Surface ◽  
Volume Of Fluid ◽  
Ring Formation ◽  
Vortex Rings ◽  
Drop Coalescence ◽  
Vortex Ring Formation ◽  
To Come

Numerical simulations using coupled level-set and volume-of-fluid (CLSVOF) method has been carried out to capture the vortex ring when a drop coalesces on a pool of liquid. A study has been done for the formation and motion of vortex rings generated when drops of liquid are allowed to come into contact at zero velocity with a quiescent flat surface of the same liquid.

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