Published Article / A stream flow at an outlet of a catchment can be entirely a base flow or direct flow or a combination of both. The base flow component of a stream is mainly contributed from the ground water storage which often is an open aquifer whereas the direct flow component is mainly the result of a direct response of a rainfall event. The Upper Modder river basin catchment is considered to be the origin of the Modder River which supplies water to Rustfontein Dam, situated at the outlet of the C52A with an area of 928 km2. Nine years of daily stream flow showed a continuous none zero discharge throughout the year. During the rainy season the discharge of the stream increases significantly. Thus, it is necessary to separate the direct and base flow of the stream in order to understand the important component that is more likely to be affected by different land use changes in a catchment. The Modder river daily mean flow at the inlet of Rustfontein dam (in Central South Africa) was analysed using four base flow separation methods, the Nathan & McMahon (N&M), the Chapman, Smakhtin & Watkins (S&W) method and the frequency duration analysis. All the methods gave higher percentage of the low flow component, except for the S&W method which underestimated it. The N&M filtering equation gave base flow components greater than 66% in 1999 and increased to 84% in 2007 while the Chapman equation revealed 65% and 74% in 1999 and 2007, respectively. Similarly, the frequency duration analysis gave 62% in 1999 and increased to 79% in 2007. The frequency duration analysis gave up to 13% lower percentage than the N&M (1990) filtering equation. The nine year base flow averages are 69%, 69% and 75% for frequency duration analysis, Chapman (1999) and N&M (1990) filtering equations, respectively. The result revealed that the Modder River is largely supplied by the ground water discharge. The result seemed to concur with the fact that for a semi-arid catchment such as the Modder river basin, with an average annual runoff coefficient of approximately 6%, the contribution of annual rainfall to direct runoff is very minimal.

A direct method is developed for solving the 2-D planar/axisymmetric Euler equations. The Euler equations are discretized using a finite-volume method with upwind flux splitting schemes, and the resulting nonlinear system of equations are solved using Newton&amp / #8217 / s Method. Both analytical and numerical methods are used for Jacobian calculations. Numerical method has the advantage of keeping the Jacobian consistent with the numerical flux vector without extremely complex or impractical analytical differentiations. However, numerical method may have accuracy problem and may need longer execution time. In order to improve the accuracy of numerical method detailed error analyses were performed. It was demonstrated that the finite-difference perturbation magnitude and computer precision are the most important parameters that affect the accuracy of numerical Jacobians. A relation was developed for optimum perturbation magnitude that can minimize the error in numerical Jacobians. Results show that very accurate numerical Jacobians can be calculated with optimum perturbation magnitude. The effects of the accuracy of numerical Jacobians on the convergence of flow solver are also investigated. In order to reduce the execution time for numerical Jacobian evaluation, flux vectors with perturbed flow variables are calculated for only related cells. A sparse matrix solver based on LU factorization is used for the solution, and to improve the Jacobian matrix solution some strategies are considered. Effects of different flux splitting methods, higher-order discretizations and several parameters on the performance of the solver are analyzed.

This thesis deals with problems related to heating of hot service water. It focuses on solar water heating, describes individual types of solar panels and summarizes the existing information about solar water heating. It demonstrates actual problems of solar system solution on a specific example of a two-generation family house, where it analyses possibilities of diagnostics and control of such system. It also deals with suggestions of possible expansion of the current solar system.