Finite element modelling of magma convection and attendant groundwater flow
- Authors: Harrison, Keith
- Date: 1998
- Subjects: Groundwater flow , Magmas
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5467 , http://hdl.handle.net/10962/d1005252 , Groundwater flow , Magmas
- Description: This thesis describes preliminary two- and three-dimensional modelling of mass and heat transport of hot, molten magma in crustal intrusions and of the associated thermally induced flow of groundwater contained in the surrounding country rock. The aim of such modelling is to create a tool with which to predict the location of mineral deposits formed by the transport and subsequent precipitation of minerals dissolved in the convecting groundwater. The momentum equations (Navier-Stokes equations), continuity equation and energy equation are used in conjunction with specially constructed density and viscosity relationships to govern the mass and heat transport processes of magma and groundwater. Finite element methods are used to solve the equations numerically for some simple model geometries. These methods are implemented by a commercial computer software code which is manipulated with a control program constructed by the author for the purpose. The models are of simple two- or three-dimensional geometries which all have an enclosed magma chamber surrounded completely by a shell of country rock through which groundwater is free to move. Modelling begins immediately after the intrusive event when the magma (in most cases rhyolitic) is at its greatest temperature. Heat is allowed to flow from the magma into the country rock causing thermal convection of the groundwater contained therein. The effect of the country rock as a porous medium on the flow of groundwater is modelled by including a distributed resistance term in the momentum equation. The computer code that controls the modelling is such that adaptions made to the models to represent real physical intrusive systems are trivial. Results of the research at this stage allow approximate prediction of the location of mineral deposits. Enhanced predictions can be made by effecting improvements to the models such as a more detailed representation of chemical processes, adaption of the computer code to allow multiple injections of magma and the modelling of frozen magma as a porous medium which admits the flow of groundwater.
- Full Text:
- Date Issued: 1998
- Authors: Harrison, Keith
- Date: 1998
- Subjects: Groundwater flow , Magmas
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5467 , http://hdl.handle.net/10962/d1005252 , Groundwater flow , Magmas
- Description: This thesis describes preliminary two- and three-dimensional modelling of mass and heat transport of hot, molten magma in crustal intrusions and of the associated thermally induced flow of groundwater contained in the surrounding country rock. The aim of such modelling is to create a tool with which to predict the location of mineral deposits formed by the transport and subsequent precipitation of minerals dissolved in the convecting groundwater. The momentum equations (Navier-Stokes equations), continuity equation and energy equation are used in conjunction with specially constructed density and viscosity relationships to govern the mass and heat transport processes of magma and groundwater. Finite element methods are used to solve the equations numerically for some simple model geometries. These methods are implemented by a commercial computer software code which is manipulated with a control program constructed by the author for the purpose. The models are of simple two- or three-dimensional geometries which all have an enclosed magma chamber surrounded completely by a shell of country rock through which groundwater is free to move. Modelling begins immediately after the intrusive event when the magma (in most cases rhyolitic) is at its greatest temperature. Heat is allowed to flow from the magma into the country rock causing thermal convection of the groundwater contained therein. The effect of the country rock as a porous medium on the flow of groundwater is modelled by including a distributed resistance term in the momentum equation. The computer code that controls the modelling is such that adaptions made to the models to represent real physical intrusive systems are trivial. Results of the research at this stage allow approximate prediction of the location of mineral deposits. Enhanced predictions can be made by effecting improvements to the models such as a more detailed representation of chemical processes, adaption of the computer code to allow multiple injections of magma and the modelling of frozen magma as a porous medium which admits the flow of groundwater.
- Full Text:
- Date Issued: 1998
The effect of different parameters on the rupture properties of leather in a tensile test
- Authors: Makhothe, Kelebohile
- Date: 1998
- Subjects: Leather -- Testing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5462 , http://hdl.handle.net/10962/d1005247 , Leather -- Testing
- Description: This thesis explores the effect of some parameters on the breaking strain, strength and the shape of the stress-strain curve of bovine leather as revealed by uniaxial tensile tests. The parameters explored are fatliquoring, moisture content, strain rate and cyclic stressing. A basic mechanical model of a simple two-dimensional weave is created and used to describe the effect of such a weave on the shape of the stress-strain curve. It is found that fatliquoring lubricates and opens up the fibre structure and thereby makes the weave more extensible. The increase in the extensibility depends on the direction in which samples are cut and therefore the manner in which the fibres are orientated. Patliquoring is observed to increase the degree to which fibres pull out at break. There are indications that the strength of fatliquored leather decreases with time of storage, while the extensibility increases. The effect of the strain rate on the breaking strain, the tensile strength and the shape of the stress-strain curve is not very clear. The stressing and releasing leather decreases the strength of leather when the fibres are orientated preferentially along the direction of the applied stresses, but has an insignificant effect in the transverse direction. It is concluded that the degree of lubrication in a weave and the orientation of the fibre bundles significantly influence the performance of leather in a test. Both moisture and fatliquoring lubricate the weave. In both the cases the degree of fibre adhesions in a weave is decreased. A well lubricated weave allows its constituent fibres to slide and align along the direction of the applied stresses, and this tends to occur before the fibres themselves areextended. Cyclic testing, at low strains, ruptures fibre adhesions and as a result induces permanent set and makes a hide softer. Most of the work done in breaking the fibre adhesion is done in the first cycle.
- Full Text:
- Date Issued: 1998
- Authors: Makhothe, Kelebohile
- Date: 1998
- Subjects: Leather -- Testing
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5462 , http://hdl.handle.net/10962/d1005247 , Leather -- Testing
- Description: This thesis explores the effect of some parameters on the breaking strain, strength and the shape of the stress-strain curve of bovine leather as revealed by uniaxial tensile tests. The parameters explored are fatliquoring, moisture content, strain rate and cyclic stressing. A basic mechanical model of a simple two-dimensional weave is created and used to describe the effect of such a weave on the shape of the stress-strain curve. It is found that fatliquoring lubricates and opens up the fibre structure and thereby makes the weave more extensible. The increase in the extensibility depends on the direction in which samples are cut and therefore the manner in which the fibres are orientated. Patliquoring is observed to increase the degree to which fibres pull out at break. There are indications that the strength of fatliquored leather decreases with time of storage, while the extensibility increases. The effect of the strain rate on the breaking strain, the tensile strength and the shape of the stress-strain curve is not very clear. The stressing and releasing leather decreases the strength of leather when the fibres are orientated preferentially along the direction of the applied stresses, but has an insignificant effect in the transverse direction. It is concluded that the degree of lubrication in a weave and the orientation of the fibre bundles significantly influence the performance of leather in a test. Both moisture and fatliquoring lubricate the weave. In both the cases the degree of fibre adhesions in a weave is decreased. A well lubricated weave allows its constituent fibres to slide and align along the direction of the applied stresses, and this tends to occur before the fibres themselves areextended. Cyclic testing, at low strains, ruptures fibre adhesions and as a result induces permanent set and makes a hide softer. Most of the work done in breaking the fibre adhesion is done in the first cycle.
- Full Text:
- Date Issued: 1998
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