Simulations of Onset of Convection in a Non-Newtonian Liquid Induced by Unsteady-State Heat Conduction

The onset of convection in an initially static non-Newtonian liquid under Fixed Surface Temperature (FST) and Constant Heat Flux (CHF) boundary conditions was simulated using a CFD package. Steady-state and unsteady-state simulations were successfully conducted for bottom surface heating of shear t...

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Main Author:	Ting, Kee Chien
Format:	Thesis
Language:	English English
Published:	2001
Subjects:	Newtonian fluids Convection (Oceanography)
Online Access:	http://psasir.upm.edu.my/id/eprint/10993/1/FK_2001_23_A.pdf
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id	my-upm-ir.10993
record_format	uketd_dc
spelling	my-upm-ir.109932011-06-09T01:22:47Z Simulations of Onset of Convection in a Non-Newtonian Liquid Induced by Unsteady-State Heat Conduction 2001-12 Ting, Kee Chien The onset of convection in an initially static non-Newtonian liquid under Fixed Surface Temperature (FST) and Constant Heat Flux (CHF) boundary conditions was simulated using a CFD package. Steady-state and unsteady-state simulations were successfully conducted for bottom surface heating of shear thinning non-Newtonian liquids. Simulations on Newtonian liquid water and glycerine were conducted to verify the simulation setup. Fourier's law of heat conduction was used to validate the steady-state simulation results. Simulations conducted for non-Newtonian liquid with Tien et al.'s (1969) experimental data were found to agree well with Fourier's law at conduction phase. Tien et al.'s definition of non-Newtonian power-law Rayleigh number was found to be inadequate in representing the onset of convection in non-Newtonian liquid. Attempts to determine the Rayleigh number for non-Newtonian liquid using apparent viscosity was successfully carried out. A more realistic critical Rayleigh number for non-Newtonian liquid was successfully determined with local values of Rayleigh number around a convection cell successfully obtained. For simulations conducted for unsteady-state heat conduction in non-Newtonian liquid, transient heat conduction theory was used to validate the results. Convection was found to occur in a continuous deep fluid bounded by two horizontal rigid surfaces and adiabatic vertical walls. Transient critical Rayleigh number for non-Newtonian liquid under unsteady state heat conduction defined by Tan (1994) was successfully applied. Transient critical Rayleigh number for non-Newtonian liquid was found to vary with flow behavior n of the Power Law model. A more realistic transient critical Rayleigh number for non-Newtonian liquid was successfully determined using apparent viscosity. Development of thermal plumes in viscous non-Newtonian liquid were found to differ slightly from the development of thermal plumes in non-viscous Newtonian liquid. The NUmax for unsteady-state simulations of Newtonian and non-Newtonian liquid were observed to be 3.8 ± 2.0 for FST cases and 2.7 ± 1.8 for CHF cases. Effect of boundary condition at interface on onset of transient convection were studied. Velocity boundary condition of a top surface solid were found to be best approximated using top-cooling simulations. Bottom-heating simulations in a deep fluid revealed that the upper interface boundary has the property between a solid and a free surface. Newtonian fluids Convection (Oceanography) 2001-12 Thesis http://psasir.upm.edu.my/id/eprint/10993/ http://psasir.upm.edu.my/id/eprint/10993/1/FK_2001_23_A.pdf application/pdf en public masters Universiti Putra Malaysia Newtonian fluids Convection (Oceanography) Faculty of Engineering English
institution	Universiti Putra Malaysia
collection	PSAS Institutional Repository
language	English English
topic	Newtonian fluids Convection (Oceanography)
spellingShingle	Newtonian fluids Convection (Oceanography) Ting, Kee Chien Simulations of Onset of Convection in a Non-Newtonian Liquid Induced by Unsteady-State Heat Conduction
description	The onset of convection in an initially static non-Newtonian liquid under Fixed Surface Temperature (FST) and Constant Heat Flux (CHF) boundary conditions was simulated using a CFD package. Steady-state and unsteady-state simulations were successfully conducted for bottom surface heating of shear thinning non-Newtonian liquids. Simulations on Newtonian liquid water and glycerine were conducted to verify the simulation setup. Fourier's law of heat conduction was used to validate the steady-state simulation results. Simulations conducted for non-Newtonian liquid with Tien et al.'s (1969) experimental data were found to agree well with Fourier's law at conduction phase. Tien et al.'s definition of non-Newtonian power-law Rayleigh number was found to be inadequate in representing the onset of convection in non-Newtonian liquid. Attempts to determine the Rayleigh number for non-Newtonian liquid using apparent viscosity was successfully carried out. A more realistic critical Rayleigh number for non-Newtonian liquid was successfully determined with local values of Rayleigh number around a convection cell successfully obtained. For simulations conducted for unsteady-state heat conduction in non-Newtonian liquid, transient heat conduction theory was used to validate the results. Convection was found to occur in a continuous deep fluid bounded by two horizontal rigid surfaces and adiabatic vertical walls. Transient critical Rayleigh number for non-Newtonian liquid under unsteady state heat conduction defined by Tan (1994) was successfully applied. Transient critical Rayleigh number for non-Newtonian liquid was found to vary with flow behavior n of the Power Law model. A more realistic transient critical Rayleigh number for non-Newtonian liquid was successfully determined using apparent viscosity. Development of thermal plumes in viscous non-Newtonian liquid were found to differ slightly from the development of thermal plumes in non-viscous Newtonian liquid. The NUmax for unsteady-state simulations of Newtonian and non-Newtonian liquid were observed to be 3.8 ± 2.0 for FST cases and 2.7 ± 1.8 for CHF cases. Effect of boundary condition at interface on onset of transient convection were studied. Velocity boundary condition of a top surface solid were found to be best approximated using top-cooling simulations. Bottom-heating simulations in a deep fluid revealed that the upper interface boundary has the property between a solid and a free surface.
format	Thesis
qualification_level	Master's degree
author	Ting, Kee Chien
author_facet	Ting, Kee Chien
author_sort	Ting, Kee Chien
title	Simulations of Onset of Convection in a Non-Newtonian Liquid Induced by Unsteady-State Heat Conduction
title_short	Simulations of Onset of Convection in a Non-Newtonian Liquid Induced by Unsteady-State Heat Conduction
title_full	Simulations of Onset of Convection in a Non-Newtonian Liquid Induced by Unsteady-State Heat Conduction
title_fullStr	Simulations of Onset of Convection in a Non-Newtonian Liquid Induced by Unsteady-State Heat Conduction
title_full_unstemmed	Simulations of Onset of Convection in a Non-Newtonian Liquid Induced by Unsteady-State Heat Conduction
title_sort	simulations of onset of convection in a non-newtonian liquid induced by unsteady-state heat conduction
granting_institution	Universiti Putra Malaysia
granting_department	Faculty of Engineering
publishDate	2001
url	http://psasir.upm.edu.my/id/eprint/10993/1/FK_2001_23_A.pdf
_version_	1747811190919135232

Simulations of Onset of Convection in a Non-Newtonian Liquid Induced by Unsteady-State Heat Conduction

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