Experiments on convective layer formation and merging in a differentially heated slot

Wirtz, R. A.; Reddy, C. S.

doi:10.1017/s0022112079000252

Cited by 21 publications

(9 citation statements)

References 7 publications

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“…The recent study of Tanny & Tsinober (1988) categorized merging as 'first' and 'subsequent ' merging and proposed a Rayleigh-number criterion for the first merging to occur. In contrast to the observations of Wirtz & Reddy (1979), they concluded that the subsequent merging did not lead to a doubling of layer thickness.…”

Section: Introductioncontrasting

confidence: 77%

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Experimental study of double-diffusive instability in sidewall heating

Jeevaraj

Imberger

1991

J. Fluid Mech.

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The response of a salinity-stratified fluid to sidewall heating is examined. Experiments were conducted using a linear salt gradient alone and with a combination of salt and thermal gradient in which the thermal stratification destabilized the density. The dominant feature of the flow was intrusions which propagated into the interior of the fluid. These were studied using shadowgraph, vertical temperature and salinity profiles, and dye streaks. Using the theory for convection in a long shallow cavity, an expression is derived for the velocity of propagation of the intrusions. The mechanism by which intrusions merge is also discussed to explain the observed formation of wavy interfaces during merging.

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Section: Introductioncontrasting

confidence: 77%

“…Merging of the unstable adjacent layers to form a stable layered system has been previously observed by Wirtz & Reddy (1979) in narrow-slot experiments. Turner & Chen (1974) also qualitatively described merging of layers in a sugar-salt system.…”

Section: Introductionsupporting

confidence: 56%

Experimental study of double-diffusive instability in sidewall heating

Jeevaraj

Imberger

1991

J. Fluid Mech.

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“…Layer thickness is therefore a quantity that cannot be discussed independently of the history of the system. The process has not been studied very extensively (but see Wirtz & Reddy 1979, McDougall 1981, Young & Rosner 2000, Ross & Lavery 2009, and the coffee table experiment in ZS13). The layer thickness increases by a process of merging of neighboring layers.…”

Section: Evolution Of the Layer Thicknessmentioning

confidence: 99%

Semiconvection: theory

Spruit

2013

A&A

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A model is developed for the transport of heat and solute in a system of double-diffusive layers under astrophysical conditions (where viscosity and solute diffusivity are low compared with the thermal diffusivity). The process of formation of the layers is not part of the model but, as observed in geophysical and laboratory settings, is assumed to be faster than the life time of the semiconvective zone. The thickness of the layers is a free parameter of the model. When the energy flux of the star is specified, the effective semiconvective diffusivities are only weakly dependent on this parameter. An estimate is given of the evolution of layer thickness with time in a semiconvective zone. The model predicts that the density ratio has a maximum for which a stationary layered state can exist, R ρ < ∼ Le −1/2 . Comparison of the model predictions with a grid of numerical simulations is presented in a companion paper.

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“…Hart (1973) considered merging of layers in the narrow-slot case and observed that it occurred owing to the breakdown of interfaces 'in a shower of turbulence and salt fingers'. Wirtz & Reddy (1979) studied in more detail the merging of layers in the narrow-slot configuration and as a result concluded that the merging process takes place by successive doubling of the layers thickness.…”

Section: Introductionmentioning

confidence: 99%

The dynamics and structure of double-diffusive layers in sidewall-heating experiments

Tanny

Tsinober

1988

J. Fluid Mech.

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The dynamics and structure of double-diffusive layers were studied experimentally by heating a linear stable solute gradient from a sidewall in a wide tank. The formation and subsequent development of the layers were investigated by various flow-visualization techniques, namely fluorescent dye, fluorescent particles and shadowgraph. Experiments were performed in order to determine the stability diagram of the flow, following in each experiment the phase trajectory of the system in the phase plane of thermal and solute Rayleigh numbers. The experimentally obtained stability diagram appears to be similar to that obtained numerically by Thangam et al. (1981) and by Hart (1971) for a vertical narrow slot and a steady basic flow. It is shown that if the temperature of the sidewall rises slowly to its prescribed value, the thickness of the initial layers, formed at the onset of instability, is a function of the ambient density gradient and fluid properties only. On the other hand, if the wall temperature rises quickly (almost impulsive heating), the thickness of the initial layers is proportional to the imposed temperature difference, provided that the Rayleigh number, based on this difference, is larger than some critical value which is associated with the first merging of the layers. A criterion for the first merging of the initial layers is obtained, and it is suggested that this merging is due to subsequent instability of the system. The subsequent merging process, following the first merging, is not a simple successive doubling of the layer thickness and in each of five nearly identical experiments a different dependence of the average layer thickness on the instantaneous Rayleigh number is obtained. This indicates that the system of layers behaves chaotically after the first merging. The final thickness of the layers depends on the prescribed lateral temperature difference, and the ratio between the final and the initial thickness of the layers is a linear function of the final Rayleigh number. Flow-visualization experiments indicate that the layers consist of vortices with vertical scale of the layer thickness and various horizontal scales.

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Experiments on convective layer formation and merging in a differentially heated slot

Cited by 21 publications

References 7 publications

Experimental study of double-diffusive instability in sidewall heating

Experimental study of double-diffusive instability in sidewall heating

Semiconvection: theory

The dynamics and structure of double-diffusive layers in sidewall-heating experiments

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