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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my-upm-ir.109932024-04-04T02:00:41Z 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%20IR.pdf text en public masters Universiti Putra Malaysia Newtonian fluids Convection (Oceanography) Faculty of Engineering Tan, Ka Kheng English |
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Universiti Putra Malaysia |
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PSAS Institutional Repository |
language |
English English |
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Tan, Ka Kheng |
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Newtonian fluids Convection (Oceanography) |
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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%20IR.pdf |
_version_ |
1804888604978184192 |