Characteristics of shearing motions in incompressible isotropic turbulence

Watanabe, Tomoaki; Tanaka, Kuniaki; Nagata, Koji

doi:10.1103/physrevfluids.5.072601

Cited by 15 publications

(74 citation statements)

References 31 publications

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“…The triple decomposition of the velocity gradient tensor (Kolář 2007; Watanabe et al. 2020) is applied to the DNS databases described above. The triple decomposition decomposes the velocity gradient tensor into three components which represent the motions of shear (), rotation () and elongation () as .…”

Section: Shear Layer Analysis Based On the Triple Decomposition Of The Velocity Gradient Tensormentioning

confidence: 99%

“…The shear layers in the planar jet are investigated with the method proposed in Watanabe et al. (2020), which examines the flow field around local maxima of . When flow structures associated with shearing motion are identified in a three-dimensional profile of , one can find at least one local maximum of in the structure.…”

Section: Shear Layer Analysis Based On the Triple Decomposition Of The Velocity Gradient Tensormentioning

confidence: 99%

“…Therefore, the vortex sheets are also called shear layers or internal shear layers (Eisma et al. 2015; Gul, Elsinga & Westerweel 2020; Watanabe, Tanaka & Nagata 2020). Several methods have been proposed to detect the location of vortex sheets in a three-dimensional velocity field in turbulence (Horiuti 2001; Horiuti & Takagi 2005; Pirozzoli, Bernardini & Grasso 2010).…”

Section: Introductionmentioning

confidence: 99%

“…It was also shown that the roll-up of shear layers causes the formation of vortex tubes (Vincent & Meneguzzi 1994; Watanabe et al. 2020).…”

Section: Introductionmentioning

confidence: 99%

“…This method was used to investigate the shear layers in homogeneous isotropic turbulence in Watanabe et al. (2020), where the shear layer orientation was successfully identified with the tensor representing shearing motion. Analysis of a three-dimensional velocity field in relation to the shear layer orientation showed that the shear layer is sustained by a biaxial strain field.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Characteristics of small-scale shear layers in a temporally evolving turbulent planar jet

Hayashi¹,

Watanabe²,

Nagata³

2021

J. Fluid Mech.

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Section: Shear Layer Analysis Based On the Triple Decomposition Of The Velocity Gradient Tensormentioning

confidence: 99%

Section: Shear Layer Analysis Based On the Triple Decomposition Of The Velocity Gradient Tensormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…It was also shown that the roll-up of shear layers causes the formation of vortex tubes (Vincent & Meneguzzi 1994; Watanabe et al. 2020).…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Characteristics of small-scale shear layers in a temporally evolving turbulent planar jet

Hayashi¹,

Watanabe²,

Nagata³

2021

J. Fluid Mech.

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Turbulence generated by an array of opposed piston-driven synthetic jet actuators

2022

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The evolution of coherent vortical structures in increasingly turbulent stratified shear layers

et al. 2022

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We study the morphology of Eulerian vortical structures and their interaction with density interfaces in increasingly turbulent stably stratified shear layers. We analyse the three-dimensional, simultaneous velocity and density fields obtained in the stratified inclined duct laboratory experiment (SID). We track, across 15 datasets, the evolution of coherent structures from pre-turbulent Holmboe waves, through intermittent turbulence, to full turbulence and mixing. We use the rortex–shear decomposition of the local vorticity vectors into a rortex vector capturing rigid-body rotation and a shear vector. We describe the morphology of ubiquitous hairpin-like vortical structures (revealed by the rortex), similar to those commonly observed in boundary-layer turbulence. These are born as relatively weak vortices around the strong three-dimensional shearing structures of confined Holmboe waves, and gradually strengthen and deform under increasing turbulence, transforming into pairs of upward- and downward-pointing hairpins propagating in opposite directions on the top and bottom edge of the shear layer. The pair of legs for each hairpin are counter-rotating and entrain fluid laterally and vertically, whereas their arched-up ‘heads’, which are transverse vortices, entrain fluid vertically. We then elucidate how this large-scale vortex morphology stirs and mixes the density field. Essentially, vortices located at the sharp density interface on either edge of the mixing layer (mostly hairpin heads) engulf blobs of unmixed fluid into the mixing layer, whereas vortices inside the mixing layer (mostly hairpin legs) further stir it, generating strong, small-scale shear, enhancing mixing. These findings provide new insights into the role of turbulent coherent structures in shear-driven stratified mixing.

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Characteristics of shearing motions in incompressible isotropic turbulence

Cited by 15 publications

References 31 publications

Characteristics of small-scale shear layers in a temporally evolving turbulent planar jet

Characteristics of small-scale shear layers in a temporally evolving turbulent planar jet

Turbulence generated by an array of opposed piston-driven synthetic jet actuators

The evolution of coherent vortical structures in increasingly turbulent stratified shear layers

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