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Everard, Kelsey Ann

University of British Columbia

Heat transport is one of the most important phenomena in environmental fluid mechanics. Of the heat transport processes, convection is by and large the most important. Convective processes in the environment, however, are rarely straightforward, necessitating investigation into the various complications that can exist for a better understanding of heat transport in real world flows. This dissertation investigates three topical problems in convective processes of environmental fluids, 1) differential cooling of a freshwater lake below the temperature of maximum density, 2) natural convection of a fluid with a temperature dependent viscosity, and 3) analysis methods of observational turbulence data. In the second chapter of this dissertation, a simple box model which describes the cooling of a freshwater lake below the temperature of maximum density is presented. Considering only the quadratic equation of state for (fresh) water and the heat fluxes due to a constant surface heat loss and a time-dependent buoyancy-driven exchange flow, reasonable predictions of the timing of ice-on (freezing) for Base Mine Lake in Alberta, Canada are obtained. In the third chapter of this dissertation, the effect of a temperature dependent viscosity on the dynamics of natural convection is explored. While an assumption of constant viscosity is appropriate for many flows involving air and water, it becomes problematic when considering the convection of fluids like silicate melts and magma which have highly temperature-dependent viscosities. Using asymptotic and numerical analysis, the effect that a temperature dependent viscosity has on buoyancy-driven convection along heated and cooled boundaries is described and quantified. In particular, the rate of heat transfer between the boundary and the fluid is solved for. Finally, in the fourth chapter of this dissertation, one of the most widely used approximations in interpreting scales from turbulence experiments is explored: Taylor's frozen eddy hypothesis (FTH). Using a novel representation of how space and time can be correlated in turbulent flows in application to temperature observations made during up-slope flow events in the roughness sublayer of the atmospheric boundary layer, a way forward for the field with regards to analysing turbulence datasets and the application of FTH is clarified.

Text

2023-12-01

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/86723

Civil Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/