AN IMPLICIT SCHEME FOR MODELING DIFFUSION USING THE SIGMA-COORDINATE SYSTEM

In this study, an implicit scheme based on finite volume formation with the sigma-coordinate system is proposed for calculating horizontal diffusion. Using conventional methods forcalculating horizontal diffusion in sigma-coordinate coastal ocean models on a steep bottom slope or wavy surface causes spurious transport (e.g. salinity, temperature, sediment, and mixingof freshwater and salt water). In this present method, transforming the sigma coordinates tostepwise meshing (an orthogonal and Non-coincided at the corner of cell meshing) and involving 3 cells at each side of each cell, enables the model to calculate diffusive transport in uneven layers more accurate. Diffusive transport plays the most important role in the distribution of turbulence. Sedimenttransport in coastal ocean or channel or cases of modeling wastewater discharges, pollutant transport, and water quality, mixing of freshwater and salt water are directly in related to diffusive transport. Comparison among analytical and numerical results confirms the accuracy of presented method for horizontal diffusive transport

Keywords:

Diffusion , Implicit Scheme , Sigma Coordinates , Stepwise Meshing , Tomas algorithm