Numerical simulation of water waves in reservoirs affecting evaporation

Greig, Edward Stephen (2013) Numerical simulation of water waves in reservoirs affecting evaporation. [USQ Project]

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Abstract

Predicted increases in evaporation rates from open water reservoirs will likely present sustainability challenges for reservoir dependent communities and industries in the next 50 years. Chemical monolayers have had highly variable success in reducing evaporation rates due breakup and transport by wind-wave action. The effect of wind-wave
stretching action on monolayers has not been quantified in the literature. The project aim was to develop a preliminary Computational Fluid Dynamics (CFD) model to
determine the average instantaneous shear stresses under wind-wave loadings corresponding to observed monolayer performance limits. Wind speeds of 0.89 m/s and 7.33
m/s are considered representative of the lower and upper limits of degraded monolayer performance. ANSYS Fluent was used to develop a preliminary model, comprising a
horizontal tank 15 m long by 0.85 m high with water occupying the bottom half. A constant uniform velocity wind profile was applied to the air inlet for up to five increments of the residence time of three wind speeds, 0.89 m/s, 4.11 m/s and 7.33 m/s. The volume of fluid method was used to capture the movement of the air/water interface.
Velocity gradients were extracted from the flow fields and following a one-way analysis of variance test, the average instantaneous shear stresses were determined to be of 0
Pa, 0.00046 Pa and 0.00058 Pa for the increasing wind speeds. These results agree with the expectation that the instantaneous shear stress would increase with increasing wind speed. Significant limitations for the preliminary model include insufficient run time and a lack of average instantaneous shear stress validation. Although this study was limited in scope, there is significant potential for model development which will assist in understanding how monolayers are affected by wind waves, and estimating and improving the operational performance of monolayers in reducing evaporation rates from open water reservoirs.


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Item Type: USQ Project
Item Status: Live Archive
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - Department of Agricultural, Civil and Environmental Engineering
Supervisors: Wandel, Andrew
Date Deposited: 21 Jan 2014 23:51
Last Modified: 09 May 2014 02:40
Uncontrolled Keywords: water waves; reservoirs; evaporation; monolayers;
Fields of Research : 09 Engineering > 0905 Civil Engineering > 090509 Water Resources Engineering
Socio-Economic Objective: D Environment > 96 Environment > 9609 Land and Water Management > 960905 Farmland, Arable Cropland and Permanent Cropland Water Management
URI: http://eprints.usq.edu.au/id/eprint/23901

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