Development and application of 3D numerical model THREETOX to the prediction of cooling water transport and mixing in the inland and coastal waters

A modelling system--THREETOX--has been developed to simulate the transport and mixing of cooling water in both freshwater and marine environment. A 3D hydrostatic free-surface model describes the heat dispersion in the far-field, whereas an integral buoyant jet model coupled with a far-field model is applied to the near-field. The equations of hydrodynamics of the far-field model are completed by equations for heat and salt transport, and by the k - ε turbulence model. Special attention is paid to the parameterization of heat fluxes between water and atmosphere and between water and bottom sediments. Wetting and drying (WAD) processes were built into the model to describe areas where tide and floods play a dominant role. The model was enhanced by processes describing the effects of ship traffic on the dispersion of the discharged heat in stagnant canals. The sigma coordinate in the upper layer can be combined in the lower layer with a second sigma coordinate system or with a z coordinate system. An orthogonal curvilinear horizontal grid with two-way nesting capabilities has been used to describe the area of interest accurately. A high order advection scheme has been applied in the model. Several examples of the application and validation of the THREETOX model are presented. Studies were performed on the dispersion of cooling water, discharged by various power plants in the Netherlands located at different types of aquatic systems, varying from rivers, canals to tidal river reaches. Copyright © 2008 John Wiley & Sons, Ltd.