A numerical investigation of impulsively generated vortical structures in deep and shallow fluid layers

The evolution and formation of large-scale turbulent coherent structures induced by an impulsive jet between non-deformable stress-free layers are investigated via direct numerical simulation at a jet Reynolds number of 1250. The ratio of the initial size of the vortex to the domain depth is varied...

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Main Authors: Watchapon Rojanaratanangkule, T. Glyn Thomas, Gary N. Coleman
Format: Journal
Published: 2018
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http://cmuir.cmu.ac.th/jspui/handle/6653943832/53905
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Institution: Chiang Mai University
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spelling th-cmuir.6653943832-539052018-09-04T10:01:19Z A numerical investigation of impulsively generated vortical structures in deep and shallow fluid layers Watchapon Rojanaratanangkule T. Glyn Thomas Gary N. Coleman Physics and Astronomy The evolution and formation of large-scale turbulent coherent structures induced by an impulsive jet between non-deformable stress-free layers are investigated via direct numerical simulation at a jet Reynolds number of 1250. The ratio of the initial size of the vortex to the domain depth is varied to study the influence of the bounding surface confinement. A non-conservative body force is applied to the governing equations to represent the momentum source. During the forcing period, the coherent structure appears in the form of a leading vortex ring together with a trailing jet, and breaks down to turbulence due to an instability very similar to theWidnall instability before interacting with the free surface. The input parameters (the momentum flux J, the forcing period Δtf, and the domain depth h) can be grouped together as the confinement number C = J1/2Δtf/h2to parameterise the intensity and strength of the eddy signature at the free surface. Increasing the confinement number corresponds to reducing the ratio of the domain depth to the initial size of the vortex, which leads to a linear increase in the maximum amplitude of the surface signature in terms of the surface eddy strength. A dipole forms for values of C greater than about unity, even though the eddy signature appears at the free surface for all the confinement numbers considered. © 2014 AIP Publishing LLC. 2018-09-04T10:01:19Z 2018-09-04T10:01:19Z 2014-01-13 Journal 10897666 10706631 2-s2.0-84905186557 10.1063/1.4864443 https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84905186557&origin=inward http://cmuir.cmu.ac.th/jspui/handle/6653943832/53905
institution Chiang Mai University
building Chiang Mai University Library
country Thailand
collection CMU Intellectual Repository
topic Physics and Astronomy
spellingShingle Physics and Astronomy
Watchapon Rojanaratanangkule
T. Glyn Thomas
Gary N. Coleman
A numerical investigation of impulsively generated vortical structures in deep and shallow fluid layers
description The evolution and formation of large-scale turbulent coherent structures induced by an impulsive jet between non-deformable stress-free layers are investigated via direct numerical simulation at a jet Reynolds number of 1250. The ratio of the initial size of the vortex to the domain depth is varied to study the influence of the bounding surface confinement. A non-conservative body force is applied to the governing equations to represent the momentum source. During the forcing period, the coherent structure appears in the form of a leading vortex ring together with a trailing jet, and breaks down to turbulence due to an instability very similar to theWidnall instability before interacting with the free surface. The input parameters (the momentum flux J, the forcing period Δtf, and the domain depth h) can be grouped together as the confinement number C = J1/2Δtf/h2to parameterise the intensity and strength of the eddy signature at the free surface. Increasing the confinement number corresponds to reducing the ratio of the domain depth to the initial size of the vortex, which leads to a linear increase in the maximum amplitude of the surface signature in terms of the surface eddy strength. A dipole forms for values of C greater than about unity, even though the eddy signature appears at the free surface for all the confinement numbers considered. © 2014 AIP Publishing LLC.
format Journal
author Watchapon Rojanaratanangkule
T. Glyn Thomas
Gary N. Coleman
author_facet Watchapon Rojanaratanangkule
T. Glyn Thomas
Gary N. Coleman
author_sort Watchapon Rojanaratanangkule
title A numerical investigation of impulsively generated vortical structures in deep and shallow fluid layers
title_short A numerical investigation of impulsively generated vortical structures in deep and shallow fluid layers
title_full A numerical investigation of impulsively generated vortical structures in deep and shallow fluid layers
title_fullStr A numerical investigation of impulsively generated vortical structures in deep and shallow fluid layers
title_full_unstemmed A numerical investigation of impulsively generated vortical structures in deep and shallow fluid layers
title_sort numerical investigation of impulsively generated vortical structures in deep and shallow fluid layers
publishDate 2018
url https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84905186557&origin=inward
http://cmuir.cmu.ac.th/jspui/handle/6653943832/53905
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