| Abstract | In recent years, there has been a· growing concern about water quality
problems associated with tidal convection and circulation in harbours and
shallow estuaries, particularly in the planning and design stages of
modifications . Presently, with the advancement in computer applications
and the deve lopment of numerical techniques, economies in time and effort
have made computer modelling a viable alternative . Many efforts have been
made with the numerical models which are more remarl{able and advantageous
than both analytical and hydraulic models, with respect to flexibility,
because the actual flow patterns and nonlinearity in boundary geometry can
be used in the computational processes . Although such models do exist, a
comprehensive analysis of the individual mechanisms which interact to
produce circulation has not been attempted with a numerical model .
This study seelrn to identify the behavioral differences caused by a
particular selection of discretization parameters and boundary
conditions . The depth-averaged two-dimensional model is performed to study
the phenomena of tidal circulation in a discrete representation of a
continuum problem, a variety of computational procedures and boundary
conditions in the model are 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 problems . In this study, the model is applied to three
partlcuJar areas of interest namely ; The whole Upper Gulf of Thailand,
The Chao Phraya river mouth and Laem Chabang Port . The details of tidal
circulation are presented according to the four predominant tidal
constituents namely ; M2,S2,Kl and 01 constituents as well as all th~ four
constituents . To test its reliability, the calibration of the model to the
current system is performed and shows the satisfactory comparison between
the computed values and predicted values of tide level obtained by the
Harmonic Analysis . Taken into account is the verification of the model to
the hourly tidal current data measured by the Hydrographic Department in
1973 . The verification was accomplished by the well simulated situation of
computed values and better tendency to improve .
The obtained results from this numerical model give the different
circulation patterns under such interferences . Furthermore, the effects of
shoreline, river and open sea boundary are also closely investigated,
particularly at the river mouth . From the macro viewpoint, the river
boundary is considered as the well simulated situation of computed values
of water level, compared with the shoreline boundary . In the micro
viewpoint, the contribution of river and shoreline boundary to the current
field can predominate only in the neighborhood of coastline at some
extents, whereas the open sea boundary, the assigned boundary values are
the major factor controlling the simulated situation of computed values of
current field . In addition to this, the effect of freshwater flow and the
restriction of the coastline configuration are also affected to those
computed values . |