Evolution of an isolated turbulent region in a stratified fluid

Fonseka, S. V.; Fernando, H. J. S.; Heijst, G. J. F. van

doi:10.1029/98jc01911

Cited by 34 publications

(4 citation statements)

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“…Most experimental studies of mixed region collapse (starting with Wu 1969) and boundary mixing (see e.g. Browand & Hopfinger 1985;Ivey & Corcos 1982;Thorpe 1982; and more recently, Phillips, Shyu & Salmun 1986;Salmun & Phillips 1992; De Silva & Fernando 1998;Fonseka, Fernando & van Heijst 1998) were made for the case of linear stratification.…”

Section: Introductionmentioning

confidence: 99%

Laboratory experiments on intrusive flows and internal waves in a pycnocline

2001

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A laboratory study has been performed to simulate intrusive flows generated by internal wave-breaking activity in the oceanic pycnocline. Two different cases were considered. In the first set of experiments a short-duration source of motion was modelled by creating a finite region of well-mixed fluid. The collapse of this region resulted in intrusive flows and internal waves in the pycnocline. Attention was focused on the formation and subsequent evolution of solitary ‘bulges’ in the intrusion. Detailed flow measurements have revealed that the weak motion inside these bulges (which contain well-mixed fluid from the source) is organized in a four-vortex structure. Numerical flow simulations provided important information about the dynamics of this four-cell structure: the outer cells are associated with baroclinic generation of vorticity, while the inner cells are characterized by a balance between the advective and the viscous terms in the vorticity equation.In the second set of experiments continuous mixing was induced by a vertically oscillating, horizontal grid centred in the pycnocline. The mixed region collapses, thus forming an intrusive flow into the pycnocline and internal waves that propagate along the pycnocline at higher speed than the intrusion. It was found that the velocity of the intrusive flow is approximately constant and that its dynamics is controlled by an inertial–buoyancy balance. The parameters of the internal waves in both cases were compared with theory.

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Section: Introductionmentioning

confidence: 99%

Laboratory experiments on intrusive flows and internal waves in a pycnocline

2001

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“…One viewpoint suggests that this large-scale coherent vortex street is actually the product of the amplification of near-field shedding vortices of the dragging sphere under the influence of the buoyancy effect of stratified fluids, causing them to be "flattened" [62]. The other viewpoint suggests that the formation of the Q2D vortex street structure is unrelated to the near-field characteristics of the dragging sphere but is caused by the shear instability of the momentum wake edge interacting with the background fluid [55,63].…”

Section: Experimental Methodsmentioning

confidence: 99%

Review on the Hydro- and Thermo-Dynamic Wakes of Underwater Vehicles in Linearly Stratified Fluid

Cao,

Pan,

Gao

et al. 2024

JMSE

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Wakes produced by underwater vehicles, particularly submarines, in density-stratified fluids play a pivotal role across military, academic, and engineering domains. In comparison to homogeneous fluid environments, wakes in stratified flows exhibit distinctive phenomena, including upstream blocking, pancake eddies, internal waves, and variations in hydrodynamic performance. These phenomena are crucial for optimizing the operation of underwater vehicles. This review critically assesses the hydrodynamic and thermodynamic aspects of these wakes through an integration of theoretical, experimental, and numerical approaches. The hydrodynamic wake evolution, comprising near-wake, non-equilibrium, and quasi-two-dimensional regimes, is scrutinized. The underlying physics, encompassing energy transformation, vertical motion suppression, and momentum dissipation, are analyzed in detail. Special emphasis is placed on numerical methods, encompassing diverse approaches and turbulence models and highlighting their differences in fidelity and computational cost. Numerical simulations not only provide insights into the intricate interplay among various factors but also emerge as a crucial focal point for future research directions. In the realm of thermodynamic wakes, we delve into the thermal wake induced by the discharge of high-temperature cooling water and the cold wake resulting from the stirring of seawater. The generation, evolution, and ascent to the free surface of these wakes are explored. Additionally, this review identifies and analyzes current research shortcomings in each aspect. By systematically addressing existing knowledge gaps, our study contributes novel insights that propel academic progress and bear significant implications for submarine engineering. This work not only enhances our understanding of the intricate dynamics involved but also provides a foundation for future research endeavors in this critical field.

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“…The evolution and collapse of a turbulent blob was studied in the laboratory, , where the maximum thickness of a blob of neutral buoyancy that emerged horizontally in a stratified fluid is proportional to L T . It seems that there are no applications of the overturning length scale in studies of the spread of turbulent jets in a natural ambient.…”

Section: Introductionmentioning

confidence: 99%