3DLIF and its applications to studies of the near field mixing in wastewater discharges.

摘要

A new 3D laser induced fluorescence (3DLIF) system was developed that is capable of measuring 3D concentration fields continuously and almost instantaneously, which is particularly suited to studies typical of wastewater discharges in various environments. The system development, and corrections and calibrations for obtaining quantitative data are described. Software was developed to enable detailed analyses of the 3DLIF data. The 3DLIF system was thoroughly tested and verified by applications to several well-studied flows. It was then applied to multi-port outfall diffusers and the Boston outfall models. Experiments were run for conditions of typical ocean outfall discharges. For all applications, both time-averaged and instantaneous 3D flow images were reconstructed, which clearly show spatial concentration distributions.; For all applications, measurements were made of the mixing characteristics of major importance to outfall design and prediction. The variation of dilution with downstream distance is highly resolved here leading to more accurate measurements of near field dilution and length. Good agreement with previous measurements and field tests were found. New data were also obtained. The assumption that a clustered multiport diffuser can be approximated as a T-shaped diffuser with the ports distributed uniformly was assessed. Lateral mixing and concentration fluctuations were also investigated. The lateral concentration profiles clearly show how individual plumes merge to become laterally uniform. The results for concentration fluctuations consistent with the argument that the end of the near field corresponds to the point where the turbulence collapse begins. After turbulence fully collapsed, the dilution levels off.; Results presented in this thesis strongly indicated that the small-scale models simulate the larger flows very well and that 3DLIF is a very effective technique for studies of ocean outfall discharges.