Experiments and Simulations on the Incompressible, Rayleigh-Taylor Instability with Small Wavelength Initial Perturbations

Persistent Link:
http://hdl.handle.net/10150/265355
Title:
Experiments and Simulations on the Incompressible, Rayleigh-Taylor Instability with Small Wavelength Initial Perturbations
Author:
Roberts, Michael Scott
Issue Date:
2012
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The Rayleigh-Taylor instability is a buoyancy driven instability that takes place in a stratified fluid system with a constant acceleration directed from the heavy fluid into the light fluid. In this study, both experimental data and numerical simulations are presented. Experiments are performed primarily using a lithium-tungstate aqueous solution as the heavy liquid, but sometimes a calcium nitrate aqueous solution is used for comparison purposes. Experimental data is obtained for both miscible and immiscible fluid combinations. For the miscible experiments the light liquid is either ethanol or isopropanol, and for the immiscible experiments either silicone oil or trans-anethole is used. The resulting Atwood number is either 0.5 when the lithium-tungstate solution is used or 0.2 when the calcium nitrate solution is used. These fluid combinations are either forced or left unforced. The forced experiments have an initial perturbation imposed by vertically oscillating the liquid containing tank to produce Faraday waves at the interface. The unforced experiments rely on random interfacial fluctuations, due to background noise, to seed the instability. The liquid combination is partially enclosed in a test section that is accelerated downward along a vertical rail system causing the Rayleigh-Taylor instability. Accelerations of approximately 1g (with a weight and pulley system) or 10g (with a linear induction motor system) are experienced by the liquids. The tank is backlit and digitally recorded with high speed video cameras. These experiments are then simulated with the incompressible, Navier-Stokes code Miranda. The main focus of this study is the growth parameter (ɑ) of the mixing region produced by the instability after it has become apparently self-similar and turbulent. The measured growth parameters are compared to determine the effects of miscibility and initial perturbations (of the small wavelength, finite bandwidth type used here). It is found that while initial perturbations do not affect the instability growth, miscibility does.
Type:
text; Electronic Dissertation
Keywords:
mixing; Rayleigh-Taylor; stratified flow; turbulence; Mechanical Engineering; fluid mechanics; instability
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Mechanical Engineering
Degree Grantor:
University of Arizona
Advisor:
Jacobs, Jeffrey W.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleExperiments and Simulations on the Incompressible, Rayleigh-Taylor Instability with Small Wavelength Initial Perturbationsen_US
dc.creatorRoberts, Michael Scotten_US
dc.contributor.authorRoberts, Michael Scotten_US
dc.date.issued2012-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe Rayleigh-Taylor instability is a buoyancy driven instability that takes place in a stratified fluid system with a constant acceleration directed from the heavy fluid into the light fluid. In this study, both experimental data and numerical simulations are presented. Experiments are performed primarily using a lithium-tungstate aqueous solution as the heavy liquid, but sometimes a calcium nitrate aqueous solution is used for comparison purposes. Experimental data is obtained for both miscible and immiscible fluid combinations. For the miscible experiments the light liquid is either ethanol or isopropanol, and for the immiscible experiments either silicone oil or trans-anethole is used. The resulting Atwood number is either 0.5 when the lithium-tungstate solution is used or 0.2 when the calcium nitrate solution is used. These fluid combinations are either forced or left unforced. The forced experiments have an initial perturbation imposed by vertically oscillating the liquid containing tank to produce Faraday waves at the interface. The unforced experiments rely on random interfacial fluctuations, due to background noise, to seed the instability. The liquid combination is partially enclosed in a test section that is accelerated downward along a vertical rail system causing the Rayleigh-Taylor instability. Accelerations of approximately 1g (with a weight and pulley system) or 10g (with a linear induction motor system) are experienced by the liquids. The tank is backlit and digitally recorded with high speed video cameras. These experiments are then simulated with the incompressible, Navier-Stokes code Miranda. The main focus of this study is the growth parameter (ɑ) of the mixing region produced by the instability after it has become apparently self-similar and turbulent. The measured growth parameters are compared to determine the effects of miscibility and initial perturbations (of the small wavelength, finite bandwidth type used here). It is found that while initial perturbations do not affect the instability growth, miscibility does.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectmixingen_US
dc.subjectRayleigh-Tayloren_US
dc.subjectstratified flowen_US
dc.subjectturbulenceen_US
dc.subjectMechanical Engineeringen_US
dc.subjectfluid mechanicsen_US
dc.subjectinstabilityen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineMechanical Engineeringen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorJacobs, Jeffrey W.en_US
dc.contributor.committeememberKerschen, Edward J.en_US
dc.contributor.committeememberFasel, Hermann F.en_US
dc.contributor.committeememberGmitro, Arthur F.en_US
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