Experimental study of brine discharge in coastal waters

• Main Author: Tay, Serene Ru-Wen.
• Other Authors: Law Wing-Keung, Adrian
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Civil engineering::Water resources
• Online Access: http://hdl.handle.net/10356/39935
• Institution: Nanyang Technological University

With the global fresh water supply diminishing, developments to desalination technologies have been done to allow it to be more economically viable. Desalination is a process which separates brine and fresh water. However, this would also lead to many environmental problems which could disrupt the ocean biodiversity. To ensure brine is disposed properly, it is essential to study the dilution and mixing characteristics of it. In this study, a series of twelve experiments were performed to investigate the mixing behaviours of a vertical negative buoyant discharges using particle image velocimetry. The aim of the experiment was to obtain curve-fitting coefficients for Reynolds shear stress equation in order to close the entrainment coefficient equation from Wang and Law (2002) second-order integral model. A detailed description of the experimental methodology is provided in the report and two experimental uncertainties encountered, namely the effects of number of samples taken and the variations in the terminal rise height, were discussed. The experimental results were subsequently extracted out using programs such as Flow Manager, Microsoft Excel and Sigma Plot to fit the Reynolds shear stress curve characterised by dual Gaussian. In addition, predictions to the velocity width being linearly proportional to axial distance for positive buoyant jets were checked for its validity on negative buoyant jet. The results obtained showed that the velocity profile and turbulent shear stress profile fit a Gaussian and dual-Gaussian profile respectively as predicted, and new curve-fitting coefficients were proposed for the turbulent shear stress equation. In addition, it was proven that velocity width is linearly proportional to axial distance for negative buoyant jets. It was suggested that further works such as studying the scalar properties of the jet would be required in order to check on the validity of the coefficients obtained.