Effect of Thermal Boundary Layer Below Water Surfaces on Evaporation

King, Alexander (2020) Effect of Thermal Boundary Layer Below Water Surfaces on Evaporation. [USQ Project]

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The thermal boundary layer is a thin layer just below the interface between the air and water. Research has shown that this layer is a lower temperature then the rest of the water body (Wells 2009). This temperature difference is thought to likely cause an impact on the evaporation rates. Many evaporation models have been developed but none are considered a complete representation of evaporation in open body water (Finch and Calver 2008). One element which has not been fully addressed is the described thermal boundary layer.

Thermal boundary layers have been proven to form in open bodies of water such as lakes and dams. To determine the effect of the thermal boundary layer in relation to the evaporation in open reservoirs and characterise which conditions will influence evaporation rates a series of Computational Fluid Dynamic (CFD) models have been created and simulated. Initially a base model was created and was validated against an accepted numerical model. This base model was then modified to simulate several thermal boundary conditions. The extent of evaporation was monitored and documented for each case. This data has been processed, and conclusions made about the effects of the Thermal Boundary Layer on evaporation.

Through this project the key outcomes are to determine under what conditions the thermal boundary layer will affect evaporation. The series of CFD models built on from each other and developed from being simple simulations to understand the capabilities of CFD in modelling evaporation to complex models to simulate close to realistic conditions. These models than had a system to allow for various combinations of the thermal boundary layers depth and temperature difference to be simulated. Results from these simulations were then compared to control simulations for determination of the effect on evaporation.

The general conclusions of the project are that the thermal boundary layer does have an impact on the rate of evaporation under certain conditions. The amount and under what circumstance depends on several factors including; presence of wind and temperature difference of the thermal boundary layer.

Following this project there is scope to further research. Notably due limitations in the CFD software and time constraints simulations there is scope for extended duration, larger domains and finer mesh. Simulations with these factors may provide for more accurate data and more conclusive outcomes.

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Item Type: USQ Project
Item Status: Live Archive
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 - 31 Dec 2021)
Supervisors: Wandel, Andrew
Qualification: Bachelor of Engineering (Honours) (Civil)
Date Deposited: 23 Aug 2021 03:58
Last Modified: 26 Jun 2023 04:08
URI: https://sear.unisq.edu.au/id/eprint/43058

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