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  • 1.
    Dia, Ben Mansour
    et al.
    King Fahd Univ Petr & Minerals, Coll Petr Engn & Geosci, CIPR, Dhahran 31261, Saudi Arabia.;King Abdullah Univ Sci & Technol, Comp Elect & Math Sci & Engn Div CEMSE, Thuwal, Saudi Arabia..
    Oppelstrup, Jesper
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.).
    Stabilizing local boundary conditions for two-dimensional shallow water equations2018In: Advances in Mechanical Engineering, ISSN 1687-8132, E-ISSN 1687-8140, Vol. 10, no 3, article id 1687814017726953Article in journal (Refereed)
    Abstract [en]

    In this article, we present a sub-critical two-dimensional shallow water flow regulation. From the energy estimate of a set of one-dimensional boundary stabilization problems, we obtain a set of polynomial equations with respect to the boundary values as a requirement for the energy decrease. Using the Riemann invariant analysis, we build stabilizing local boundary conditions that guarantee the stability of the hydrodynamical state around a given steady state. Numerical results for the controller applied to the nonlinear problem demonstrate the performance of the method.

  • 2.
    Paul, Seema
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Oppelstrup, Jesper
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA.
    Hydro-meteorological processes driving solute transport in Lake VictoriaManuscript (preprint) (Other academic)
    Abstract [en]

    This study explores by a vertically integrated tracer transport model, hydro-meteorological event characteristics and their influence on solute transport. Changes in Hydro-meteorological processes and increasing frequency of extreme weather events are responsible for changing the lake water balance, influencing streamflow variations, and lake tracer transport. We compare historical data over a long time with model data from a vertically integrated model in Comsol Multiphysics. We consider water balance, sources of data uncertainty, correlations, extreme rain and inflow years, and seasonal variations. The lake transport model has estimated soluble loading and transportation. The results showed that the lake rainfall is seasonal; there are strong correlations between tributary inflows and precipitation, and between lake outflow and water level. It was found that “events” influence lake level fluctuations. The solute transport was shown to vary more in wet periods. Modeled transportations were higher in Kenya and Uganda lake zones than in Tanzanian zones. The major inflow, from the Kagera river, appears to strongly influence lake solute transportation, so the composition of this river must be considered.

  • 3.
    Paul, Seema
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Oppelstrup, Jesper
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Numerical Analysis, NA.
    Thunvik, Roger
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Mango Magero, John
    Makerere University.
    DDumba Walakira, David
    Makerere University.
    Cvetkovic, Vladimir
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
    Bathymetry Development and Flow Analyses Using Two-Dimensional Numerical Modeling Approach for Lake Victoria2019In: Fluids, ISSN 2311-5521, Vol. 4, no 4, p. 1-21Article in journal (Refereed)
    Abstract [en]

    This study explored two-dimensional (2D) numerical hydrodynamic model simulations of Lake Victoria. Several methods were developed in Matlab to build the lake topography. Old depth soundings taken in smaller parts of the lake were combined with more recent extensive data to produce a smooth topographical model. The lake free surface numerical model in the COMSOL Multiphysics (CM) software was implemented using bathymetry and vertically integrated 2D shallow water equations. Validated by measurements of mean lake water level, the model predicted very low mean flow speeds and was thus close to being linear and time invariant, allowing long-time simulations with low-pass filtered inflow data. An outflow boundary condition allowed an accurate simulation to achieve the lake’s steady state level. The numerical accuracy of the linear measurement of lake water level was excellent.

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