| Author | Narasimhan, Sriram |
| Call Number | AIT Thesis no.WM-95-04 |
| Subject(s) | Diffusion in hydrology
|
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Civil Engineering |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. WM-95-04 |
| Abstract | In the mathematical modelling of the diffusion or dispersion process caused by wastes or any pollutant, the diffusion coefficient plays an important role. In this study the diffusion coefficient is calculated using the statistical procedure of removing periodicity from the tidal current data using Harmonic Analysis. The Hydrodynamic and Water-Quality models based on Finite-difference formulations are used to study the variations of flow patterns and distribution patterns of some water quality parameters in the Upper Gulf of Thailand. The Hydrodynamic model is based on the conservation of water mass and momentum equations, vertically averaged over the whole water depth, while the dispersion model is based on the vertically averaged substance balance equation. The depth averaged two dimensional model is used to study the tidal circulation in a discrete representation of a continuum problem with a variety of computational procedures and boundary conditions which are currently available. By using the so-called Alternating Direction Implicit (ADI) finite difference scheme, a combination of implicit and explicit schemes, the numerical model is developed to achieve the proposed solutions. In this study the model is applied to two main areas of interest. One is the whole Upper Gulf and the other is the mouth of the Chao Phraya River. To test it's reliability the calibration of the results is performed and shows satisfactory comparison of observed and computed current speed and direction. The verification was also performed using the tidal current measured at an entirely different period of time. An attempt is made to develop a Water Quality model using finite-difference approximations and neglecting the decay term so that the pollutant can be assumed as unsettling mud. It was found from this Study that the Diffusion Coefficient along the North-South direction was higher than in the East-West direction which agrees well with the strong tidal Current condition in the Nmih-South direction in the area. There is also a need to study the reasons for the periodicity observed in the Auto-Correlation Analysis for the calculation of Diffusion Coefficient even after complete removal of the periodic components. The Study also revealed that the effect of the fresh water flows is restricted to a limited area in the vicinity of the river mouth and hence the flood water flows do not have a significant effect on the pollution of the entire Upper Gulf of Thailand |
| Year | 1995 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. WM-95-04 |
| Type | Thesis |
| School | School of Civil Engineering |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Water Engineering and Management (WM) |
| Chairperson(s) | Suphat Vongvisessomjai; |
| Examination Committee(s) | Sutat Weesakul;Harumichi, Kyotoh;Hansen, Ian Sehested; |
| Scholarship Donor(s) | DANIDA; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1995 |