Modelling of saline intrusion in a long sea outfall

摘要

In this paper, the results of an investigation into the internal hydraulics of a long sea outfall are presented. The investigation focuses on the mixing and stratification of the saline receiving water and the discharged wastewater within the outfall diffuser. The research methods include a combination of numerical modelling and laboratory testing.rnThe paper provides details of an enhanced numerical model of outfall operation. The model is designed to reproduce the internal hydraulics of the outfall including buoyancy and stratification, so that the interaction between the saline sea water and the effluent may be predicted.rnThe numerical model has been developed using the FLUENT/UNS computational fluid dynamics (CFD) package. Mixing and transport of the two fluids at the saline/wastewater interface are modelled using 'chemical species', which simulate convection and diffusion on a molecular level.rnThe paper refers to physical model tests carried out using a scale model of a typical modern outfall diffuser discharging, under simplified conditions, into still receiving waters. Also included is a discussion on the dominant physical processes and the methods of scaling used to recreate saline intrusion under laboratory conditions.