No description available.

No description available.

Heat transfer and fluid flow characteristics for natural convection of air in a vertical parallel channel system have been examined. The results of both theoretical and experimental work are reported in this thesis. The system of differential equations governing the fluid flow was solved using the PHOENICS code program. The PHOENICS solution gave velocities, temperatures and pressures throughout the field and velocity and temperature profiles are presented at different vertical locations for three channel heights, 1,2 and 3 m, each for three different channel widths, 50,100 and 150 mm. A further PHOENICS sub-routine was written to obtain relevant dimensionless parameters such as the Nusselt Number, which characterises the heat transfer to the air, the Rayleigh Number, the dimensionless air flow rate and dimensionless channel length. The results obtained have been compared with experimental results and with existing data for channels with constant wall temperatures. Non-isothermal wall cases were also considered and the resulting velocity and temperature profiles are presented. The channel used in the experimental work was formed from two vertical plates, one of which was electrically heated, while the other was glass. Heated plates of height 1m and 2m were used and combination of these formed a plate of height 3 m. The width of the plates was 1 m. A double glazed cover plate of the same dimensions could be adjusted to give spacings between the heated plate and glass from 25 mm to 150 mm. The electrically heated plate could be controlled to give the required constant plate temperature (range 35-125°C) and heating could be augmented by a solar simulator consisting of 50 Tungsten Halogen Lamps of 150 Watts each. From the experimental results, relationships between the Nusselt number, Rayleigh number, dimensionless air flow rate and dimensionless channel height have been obtained. In addition, the effect of diffuser sections at the channel inlet and outlet and transient operating conditions were investigated experimentally. Effects of atmospheric pressure and humidity were also considered. The experimental results are compared with those from the PHOENICS solution and with existing data for constant wall temperature conditions and they show good agreement. A discussion of the use of the correlating equations for the heat transfer coefficient and air flow rate in the design of passive solar heating systems, such as the Trombe wall, is also included.

Aspects of thermal convection in the Earth's fluid core in the presence of a strong azimuthal magnetic field may be understood by considering a horizontal plane layer, rotating about the vertical z axis, with gravity acting downwards and containing an applied magnetic field aligned in the y (azimuthal) direction. Since the OMB is not smooth, the effects of adding bumps (with axes perpendicular to the applied magnetic field) to the top boundary of the layer are investigated in the magnetogeostrophic limit. The arbitrary geostrophic flow that arises under this limit is evaluated using a modified Taylor constraint. The bumps distort the isotherms so that they are not aligned with equipotential surfaces, leading to an imperfect configuration. This means that a hydrostatic balance is not possible, and motion ensues. This motion takes the form of a steady transverse convection roll, with axis parallel to the bumps. The roll exists for all values of the Rayleigh number, except that value for which the corresponding homogeneous problem in the standard plane layer has a solution. The roll obeys Taylor's constraint, and has no associated geostrophic flow. The stability of this roll to perturbation by oblique rolls (which are preferred for 0(1) values of the Elsasser number) is considered. It is found that the most unstable linear mode consists of a pair of these oblique rolls, aligned so that no geostrophic flow is accelerated by their interaction with the basic state. Hence, the stability results obtained here are identical to those found by perturbing the hydrostatic conduction solution with oblique rolls in the standard layer. Finally, the nonlinear evolution through the Ekman regime of these linear instabilities is considered. It is found that the nonlinear convection behaves similarly to mean field dynamo models which incorporate a geostrophic nonlinearity. Various types of Ekman solution are found, and evolution to Taylor states is observed.

No description available.

Graduation date: 2000

Thesis (Ph.D.)--Australian National University, 2001.

Thesis (Ph. D.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on June 10, 2009) Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (p. [109]-117).

Includes bibliographical references (p. 123-130).