Application of two turbulence closure schemes in the modelling of tidal currents and salinity in the Hooghly Estuary

This paper has two purposes. The first is to study the circulation and sali nity in Hooghly Estuary, along the east coast of India and the second is to compare the performance of two turbulence closure schemes by modelling it. A breadth averaged numerical model using a sigma co-ordinate system in the vertical is briefly described. Vertical diffusion of momentum and salt are parameterized by a simple first-order turbulent closure or by a one equati on model for turbulent kinetic energy (TKE) which uses a specified mixing l ength. The results are compared with the available neap and spring tide obs ervations along the estuary for both low and high discharge periods. The computed elevations and currents are in reasonable agreement with the o bservations showing no major differences in vertical current profiles by bo th the turbulent schemes. However, there is a slight under-prediction of bo ttom currents. The salinity profiles predicted by TKE model show better mat ching with observations. Statistical tests are also conducted to study the comparative performance of the turbulent closure schemes. The maintenance o f two layer structure in residual currents and salt variability are also st udied by using the model. (C) 1999 Academic Press.