Dynamics of asymmetric stratified shear instabilities

Olsthoorn, Jason; Kaminski, Alexis; Robb, Daniel M.

doi:10.1103/physrevfluids.8.024501

Cited by 9 publications

(5 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, flows with asymmetric background profiles may exhibit instabilities with a mixture of KH- and Holmboe-like behaviour (e.g. Carpenter, Lawrence & Smyth 2007; Yang, Tedford & Lawrence 2019; Olsthoorn, Kaminski & Robb 2023). Understanding how boundary proximity affects these processes may provide insights on future parameterizations of mixing in the ocean near boundaries.…”

Section: Summary and Discussionmentioning

confidence: 99%

The effects of boundary proximity on Kelvin–Helmholtz instability and turbulence

2023

Self Cite

View full text Add to dashboard Cite

Studies of Kelvin–Helmholtz (KH) instability have typically modelled the initial flow as an isolated shear layer. In geophysical cases, however, the instability often occurs near boundaries and may therefore be influenced by boundary proximity effects. Ensembles of direct numerical simulations are conducted to understand the effect of boundary proximity on the evolution of the instability and the resulting turbulence. Ensemble averages are used to reduce sensitivity to small variations in initial conditions. Both the transition to turbulence and the resulting turbulent mixing are modified when the shear layer is near a boundary: the time scales for the onset of instability and turbulence are longer, and the height of the KH billow is reduced. Subharmonic instability is suppressed by the boundary because phase lock is prevented due to the diverging phase speeds of the KH and subharmonic modes. In addition, the disruptive influence of three-dimensional secondary instabilities on pairing is more profound as the two events coincide more closely. When the shear layer is far from the boundary, the shear-aligned convective instability is dominant; however, secondary central-core instability takes over when the shear layer is close to the boundary, providing an alternate route for the transition to turbulence. Both the efficiency of the resulting mixing and the turbulent diffusivity are dramatically reduced by boundary proximity effects.

show abstract

Section: Summary and Discussionmentioning

confidence: 99%

The effects of boundary proximity on Kelvin–Helmholtz instability and turbulence

2023

Self Cite

View full text Add to dashboard Cite

show abstract

“…5o). These asymmetric stratified shear flows have attracted recent attention following field observations (e.g Tu et al, 2020;Olsthoorn et al, 2023). Previous work on K-H billows has highlighted the role of 3-D instabilities beyond the point at which billows coalesce.…”

Section: Discussionmentioning

confidence: 98%

A new approach to understanding fluid mixing in process-study models of stratified fluids

Hartharn-Evans,

Stastna,

Carr

2024

Nonlin. Processes Geophys.

View full text Add to dashboard Cite

Abstract. While well-established energy-based methods of quantifying diapycnal mixing in process-study numerical models are often used to provide information about when mixing occurs, and how much mixing has occurred, describing how and where this mixing has taken place remains a challenge. Moreover, methods based on sorting the density field struggle when the model is under-resolved and when there is uncertainty as to the definition of the reference density when bathymetry is present. Here, an alternative method of understanding mixing is proposed. Paired histograms of user-selected variables (which we abbreviate USPs (user-controlled scatter plots)) are employed to identify mixing fluid and are then used to display regions of fluid in physical space that are undergoing mixing. This paper presents two case studies showcasing this method: shoaling internal solitary waves and a shear instability in cold water influenced by the nonlinearity of the equation of state. For the first case, the USP method identifies differences in the mixing processes associated with different internal solitary wave breaking types, including differences in the horizontal extent and advection of mixed fluid. For the second case, the method is used to identify how density and passive tracers are mixed within the core of the asymmetric cold-water Kelvin–Helmholtz instability.

show abstract

“…Furthermore, flows with asymmetric background profiles may exhibit instabilities with a mixture of KH-and Holmboe-like behaviour (e.g. Carpenter et al 2007;Yang et al 2019;Olsthoorn et al 2023). Understanding how boundary proximity affects these processes may provide insights on future parameterizations of mixing in the ocean near boundaries.…”

Section: Summary and Discussionmentioning

confidence: 99%

The effects of boundary proximity on Kelvin-Helmholtz instability and turbulence

Liu¹,

Smyth²,

Kaminski³

2023

Preprint

View full text Add to dashboard Cite

Studies of Kelvin-Helmholtz (KH) instability have typically modelled the initial flow as an isolated shear layer.In geophysical cases, however, the instability often occurs near boundaries and may therefore be influenced by boundary proximity effects. Ensembles of direct numerical simulations are conducted to understand the effect of boundary proximity on the evolution of the instability and the resulting turbulence. Ensemble averages are used to reduce sensitivity to small variations in initial conditions. Both the transition to turbulence and the resulting turbulent mixing are modified when the shear layer is near a boundary: the time scales for the onset of instability and turbulence are longer, and the height of the KH billow is reduced. Subharmonic instability is suppressed by the boundary because phase-lock is prevented due to the diverging phase speeds of the KH and subharmonic modes. In addition, the disruptive influence of three-dimensional secondary instabilities on pairing is more profound as the two events coincide more closely. When the shear layer is far from the boundary, the shear-aligned convective instability is dominant; however, secondary central core instability takes over when the shear layer is close to the boundary, providing an alternate route for the transition to turbulence. Both the efficiency of the resulting mixing and the turbulent diffusivity are dramatically reduced by boundary proximity effects.

show abstract

Dynamics of asymmetric stratified shear instabilities

Cited by 9 publications

References 59 publications

The effects of boundary proximity on Kelvin–Helmholtz instability and turbulence

The effects of boundary proximity on Kelvin–Helmholtz instability and turbulence

A new approach to understanding fluid mixing in process-study models of stratified fluids

The effects of boundary proximity on Kelvin-Helmholtz instability and turbulence

Contact Info

Product

Resources

About