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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| Format: | Thesis |
| Language: | English English |
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2001
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| Online Access: | http://psasir.upm.edu.my/id/eprint/10993/1/FK_2001_23%20IR.pdf |
| _version_ | 1796968015348105216 |
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| author | Ting, Kee Chien |
| author_facet | Ting, Kee Chien |
| author_sort | Ting, Kee Chien |
| collection | UPM |
| 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. |
| first_indexed | 2024-03-06T07:22:17Z |
| format | Thesis |
| id | upm.eprints-10993 |
| institution | Universiti Putra Malaysia |
| language | English English |
| last_indexed | 2024-04-09T03:50:16Z |
| publishDate | 2001 |
| record_format | dspace |
| spelling | upm.eprints-109932024-04-04T02:00:41Z http://psasir.upm.edu.my/id/eprint/10993/ Simulations of onset of convection in a non-newtonian liquid induced by unsteady-state heat conduction 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. 2001-12 Thesis NonPeerReviewed text en http://psasir.upm.edu.my/id/eprint/10993/1/FK_2001_23%20IR.pdf Ting, Kee Chien (2001) Simulations of onset of convection in a non-newtonian liquid induced by unsteady-state heat conduction. Masters thesis, Universiti Putra Malaysia. Newtonian fluids Convection (Oceanography) English |
| spellingShingle | Newtonian fluids Convection (Oceanography) Ting, Kee Chien Simulations of onset of convection in a non-newtonian liquid induced by unsteady-state heat conduction |
| title | 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_short | 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 |
| topic | Newtonian fluids Convection (Oceanography) |
| url | http://psasir.upm.edu.my/id/eprint/10993/1/FK_2001_23%20IR.pdf |
| work_keys_str_mv | AT tingkeechien simulationsofonsetofconvectioninanonnewtonianliquidinducedbyunsteadystateheatconduction |