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    Numerical simulation of water-quality model on flooding using revised lax-diffusive and modified siemieniuch-gladwell methods
    (2019-12-01)
    Subklay, Kanawoot
    ;
    Pochai, Nopparat
    In 2011, Thailand has been confronted a largest flooding. The mass of water has been drenched from many main and branch rivers to cover wide areas. The residents who lived in the flooding area have to build a manmade sandbag dike to protect their village. The flooding has been taken for a long time meanwhile the flooding water becomes contaminated. There are some residents in their flooding area want to drain their contaminated water to a nearest area. They have been destroyed their sandbag dike. Consequently, the dispute among residents is occurred. In this research, a mathematical simulation of a water-quality on a long period flooding using a couple of two models is proposed. The first model is the one-dimensional shallow water equations that provide the water elevation and velocity. The second model is a one-dimensional advection-dispersion equation that provides the water pollutant concentrations after the sandbag dike has been destroyed. A revised Lax-diffusive is used to approximate the solution of the first model. Consequently, the numerical solutions of the second model are obtained by using the traditional and modified Siemieniuch-Gladwell schemes.
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    Numerical simulations of a water quality model in a flooding stream due to dam-break problem using implicit and explicit methods
    (2017-02-17)
    Subklay, Kanawoot
    ;
    Pochai, Nopparat
    The heavy monsoon rains have been drenched flooding along the rivers and reservoirs. The residents try to construct the sandbag dike to protect their village. If the residents have encountered flood for long period, the water pollutant must be increase. The villagers want to drain the water to another areas. The residents of another village are not agree to receive the drained-polluted water from them. The simulation of water-quality is required to compromise these problem. The simulation process of water-quality model is require the input as the water flow velocities after the villagers dike has been destroyed but there is lack of field data on the flooding period. In this research, the dam-break model is used to describe unsteady dike failure flow. A couple of mathematical models is used to simulate water-quality in the problem. The first model is the dam-break model that provides the velocity fields and elevation of water. The second model is the dispersion model that provides the pollutant concentration fields. A modified Lax-diffusive method for solving a dam-break model is proposed. At each step, the flow velocity fields calculated from the first model are the input into the second model as the field data. The explicit and implicit methods are subsequently employed in the dispersion model. This paper proposes a simply remarkable alteration to the Lax-diffusive method, the implicit methods and the explicit methods so as to make it more accurate without any significant loss of computational efficiency. The numerical techniques indicate that this model can be applied for simulation of water-quality in long-term flooding cases are proposed.
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    An optimal control of water pollution in a stream using a finite difference method
    (2011-08-01)
    Pochai, Nopparat
    ;
    Deepana, Rujira
    Water pollution assessment problems arise frequently in environmental science. In this research, a finite difference method for solving the one-dimensional steady convection-diffusion equation with variable coefficients is proposed; it is then used to optimize water treatment costs.
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    A numerical computation of a non-dimensional form of stream water quality model with hydrodynamic advection-dispersion-reaction equations
    (2009-11-01)
    Pochai, Nopparat
    Mathematical models of water quality assessment problems often arise in environmental science. The modelling often involves numerical methods to solve the equations. In this research, two mathematical models are used to simulate pollution due to sewage effluent in the nonuniform flow of water in a stream with varied current velocity. The first is a hydrodynamic model that provides the velocity field and elevation of the water flow. The second is a dispersion model, where the commonly used governing factor is the one-dimensional advection-dispersion-reaction equation that gives the pollutant concentration fields. In the simulation processes, we used the Crank-Nicolson method system of a hydrodynamic model and the backward time central space scheme for the dispersion model. Finally, we present a numerical simulation that confirms the results of the techniques. © 2009 Elsevier Ltd. All rights reserved.