ABSTRACT
Many real processes in hydraulics involve continuous variations of conditions (e.g., river or tidal flow). Continuously varying processes may be represented in various ways (e.g., by scale models or electrical circuits); however, computational hydraulics has assumed an increasing role in research and design and may be seen as the culmination of centuries of development in the study of fluid flows. Many sophisticated software packages are now available, which can be operated with a minimum of training. Even so, it is important that an engineer using such software should be aware of the assumptions that underlie it, the methods used and the possible shortcomings. This chapter provides an understanding of the terms mathematical, numerical and computational model and how to transform a partial differential equation into a finite difference scheme. The importance of convergence, consistency and stability to a numerical scheme and how to set up the partial differential equations representing a simple unsteady flow, discretise them and structure the corresponding program for a computer are detailed. This is followed by a discussion of how to set the initial and boundary conditions and provide the appropriate data for the program to run. Finally, the need to calibrate and verify computer models against field data is emphasised. Some worked examples are given in the text.
