Abstract:

The desalination industry is undergoing a fast development in the world due to water shortage and significant reduction in production cost in recent years. For environmental concerns, a proper design of the brine outfall is essential to enable the end discharge mix rapidly with the ambient coastal waters. A widely adopted practice is an inclined round submerged discharge at the seabed, with an inclination angle of 60° to the horizontal to optimize the mixing efficiency. However, the maximum rise height associated with 60° is relatively large and thus unsuitable for disposal in shallow coastal wasters. In this study, the authors investigated the mixing efficiency of a submerged round brine discharge at smaller angles (30° and 45°) by using advanced laser diagnostic approach of combined Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF). Based on the experimental results, characteristic geometrical features were identified in dense discharge flow, such as terminal rise height and horizontal location and dispersion degree of the impact point, where the downward flow impinges the base. The results may be of regulatory reference for the mixing pattern of the brine plume in surrounding coastal waters.

Key words: desalination, discharges, shallow waters, PIV, PLIF