DEVELOPMENT AND VALIDATION OF THREE-DIMENSIONAL HYDRODYNAMIC AND TRANSPORT MODELS

Abstract

A three-dimensional multilevel hydrodynamic model has been developed based on finite differences using an explicit scheme for time integration. A third-order upwind scheme has been used for the convective terms of the momentum equations, to minimise the effects of numerical diffusion. The three-dimensional hydrodynamic model developed has been validated by comparing the results obtained in the model, with that given by the analytical solution, under idealised conditions. The steady state velocities over the depth and the free surface elevations obtained using the model for the cases of wind and density driven circulations compare well with that given by the analytical solution and are found to be closer to the analytical solution, with the increasing number of layers. The model's formulation or the nonlinear terms has been validated, by taking the case of circulation induced by wind and Coriolis force. The steady state velocities and free surface elevations obtained for the case of circulation induced by wind and Coriolis force compare well with that given by another numerical solution. A three-dimensional transport: model has also been developed based on a finite difference method, using an explicit scheme for time integration. As in the case of hydrodynamic model, a third order upwind scheme has been used for the convective terms of the three-dimensional convection-diffusion equation, to minimise the effects of numerical diffusion. The developed three-dimensional transport model has been tested against analytical solutions for various cases of transport of point source and Gaussian pulse pollutant sources by convection and diffusion. The concentration distributions obtained using the numerical model compare well with that given by the analytical solution for the various test cases. The dispersion behaviour of a instantaneous point source in a rectangular basin, under the influence of the flow field, driven by a cosine tide is investigated using the three-dimensional transport model.