As apart of a research project, financially supported by the CDL, to study the thermal effects of waste heat discharged into natural water recipients, this report describes a numerical model for this purpose anda number of verifications against real data.
The model is based on the conservation laws for mass momentum and energy. It is time-dependent, three-dimensional and has the possibility of using a varying horizontal resolution depending on the nature of the problem.
A coordinate transformation in the vertical direction gives the model the same number of calculating points in the vertical all over the modelled area, which increases the confidence in the vertical description considerably. This is of great value, as most of the discharges and the pollution problems are in shallow areas, where other medels in general will have a poor resolution.
Applications of the model to different types of recipients are presented and the effects of important mixing mechanisms are illustrated. The model results have been verified against field measurements, and important plume characteristics like area of heated surface water, vertical extent of the plume,and centerline temperature decay have all been successfully simulated. The verification study demonstrates in addition that recirculation of cooling water is well described by the model.
The verification studies suggest enlarged use of this type of model studies both in the planning of new locations for power plants and in the monitoring of the environmental effects of the discharged heat.
This model can be used both to predict thermal effects in the immediate neighbourhood of the power plant and to predict distribution and long term variations in wider surroundings. Of special interest is the use of the model when locations of the inlet and outlet are to be considered.