Mixing of Heated Water Discharged in the Surf Zone

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Abstract
In this paper, a description is given on the mixing processes of heated water discharged into the surf zone, based on the field investigations. In accordance with the flow characteristics observed, the flow region can be classified into three parts, namely the jet flow region, nearshore current region and coastal current region. In the jet flow region, the flow characteristics are expressed well by the two dimensional turbulent jet flow model and strongly influenced by the cuspate bottom configuration formed under the interaction between the jet flow and nearshore currents. It is realized that the dacay of plume centerline temperature is slower than the other cases owing to the influence of bottom slope, water depth and the direction of jet axis. By the dye tracer studies, in the nearshore current region the variance increases approximately with time at a power of 1.72 for longitudinal and of 1.95 for lateral respectively, while the diffusion coefficient increases with diffusion scale at a power of 1.43 for longitudinal and of 1.71 for lateral respectively. In the coastal current region, the representative isotherms are mainly in appearance either of the southerly alongshore or northerly stretch, possibly caused by some fairly long period waves. The cloud of heated water was always confined within a certain strip of nearshore zone, likely in response to the existence of a turbulent boundary layer phenomena appeared in parallel to the coastline. Quantitative modelling of this resulting plume is then made. In addition, some pulsation patterns of isotherms were also observed. Finally, a graphical representation of the functional relationship between the relative temperature difference and the area within the specified isotherm is shown.

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