Author(s): L. Toombes; H. Chanson
Linked Author(s):
Keywords: Basic equations; Numerical modelling; Physical modelling; Limitations
Abstract: Fluid motion is controlled by the basic principles of conservation of mass, energy and momentum, which form the basis of fluid mechanics and hydraulic engineering. Complex flow situations must be solved using empirical approximations and numerical models, which are based on derivations of the basic principles (backwater equation, Navier-Stokes equation etc). All numerical models are required to make some form of approximation to solve these principles, and consequently all have their limitations. Sadly, these limitations are usually neither advertised by the software developers, nor investigated and understood by the users. The consequences of misusing a model can be catastrophic. This paper presents a brief explanation of the backwater and Navier-Stokes equations, and examines the use of these equations in the context of several leading software packages. The major assumptions and approximations implicit in both the base equations and numerical models are identified, together with the limitations that these impose. The validity of the numerical models is then examined in a number of situations, including verification of the model predictions against physical model data.
Year: 2011