Theoretical analysis of vorticity in a hairpin vortex in the viscous sublayer of a laminar boundary layer

Lin, Liming; Wu, Ying

doi:10.1016/j.euromechflu.2022.03.002

Cited by 6 publications

(1 citation statement)

References 38 publications

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“…The interaction of the separation flow and the downflow generates a system of horseshoe vortices that envelope the base of the obstacle. Horseshoe vortex structures are unstable, change their shape, number, circulation and location, interact with each other and the streamlined surface, pair and break under the action of Reynolds and viscous stresses ( Rona et al., 2020 ; Robison et al., 2021 ; Qi et al., 2022 ; Lin and Wu, 2022 ). On the lateral sides of the bluff body, separated shear layers are formed.…”

Section: Introductionmentioning

confidence: 99%

Junction flow inside and around three-row cylindrical group on rigid flat surface

Voskoboinick

Onyshchenko²,

Voskoboinyk³

et al. 2022

Heliyon

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Section: Introductionmentioning

confidence: 99%

Junction flow inside and around three-row cylindrical group on rigid flat surface

Voskoboinick

Onyshchenko²,

Voskoboinyk³

et al. 2022

Heliyon

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Indirect physical mechanism of viscous forces: Vortex stretching and twisting

Lin

2022

Physics of Fluids

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In this paper, the indirect physical mechanism of viscous forces, \ie vortex stretching and twisting, is theoretically explored. The local flow in the immediate neighborhood of a flat plate is analyzed. Only the viscous forces are considered. By introducing oppositely-signed streamwise vorticity in such a region, the induced velocity and vorticity fields are obtained. Because the induced streamwise velocity varies along both the wall-normal and spanwise directions, induced vertical and spanwise vorticities are generated. The induction sequence is firstly clarified. Then two indirect effects of viscous forces are identified. The induced spanwise vorticity leads to the original two-dimensional spanwise vorticity increasing and decreasing alternately across the span, as the vortex stretching effect of viscous forces. The local spanwise vortex is distorted at positions where the streamwise vorticity is introduced, and the appearance of induced vertical vorticity at the same positions enhances this effect, as the vortex twisting effect of viscous forces.

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Physical origin of vortex stretching and twisting: Viscous or inertial forces

Lin

2022

Physics of Fluids

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In this paper, the physical origin of vortex stretching and twisting is theoretically investigated. The effects of inertial and viscous forces are mainly considered and discussed. Two key conditions, i.e., solid walls and three-dimensional (3D) disturbances, are adopted in three typical cases. Among them, the first two cases are straight and curved vortex lines at the initial time without any kind of disturbance. The third case is a straight vortex line at the initial time with introduced 3D natural disturbances. Through experimental observations, numerical simulations and theoretical analysis in these cases, the first two cases illustrate that the straight or curved vortex lines are still straight or curved at the next time, respectively, regardless of whether solid walls are introduced. However, the third case clearly shows that once natural disturbances are introduced, the straight vortex lines near and at solid walls at the initial time are stretched and twisted mainly by viscous forces, instead of inertial forces, typically demonstrated by the 3D wake transition of a straight circular cylinder and the transition of the laminar boundary layer at a flat plate. Accordingly, based on definitions of generation and enhancement in vortex stretching and twisting, it is confirmed that the viscous forces with two key conditions are the generation mechanism, while the inertial forces alone are the enhancement mechanism.

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Theoretical analysis of vorticity in a hairpin vortex in the viscous sublayer of a laminar boundary layer

Cited by 6 publications

References 38 publications

Junction flow inside and around three-row cylindrical group on rigid flat surface

Junction flow inside and around three-row cylindrical group on rigid flat surface

Indirect physical mechanism of viscous forces: Vortex stretching and twisting

Physical origin of vortex stretching and twisting: Viscous or inertial forces

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