ABSTRACT
The task of turbulence models is to determine the turbulent transport terms appearing in the mean-flow equations so that these can be solved and hence the velocity, temperature and concentration fields be obtained. This chapter assesses how well, the existing models fulfil this task for hydraulic flow problems. At present, two-equation models, and in particular the k-ε model, are the most widely-tested ones for hydraulic flow problems. With modern numerical techniques two-equation models are not much more expensive to use than one-equation models or even the mixing-length hypothesis. The comparison with experiments has shown that the k-ε model is capable of predicting afairly large variety of basic hydraulic flow situations with the same empirical input. The depth-average version of the model was also shown to be successful and may be sufficient in many situations where the flow bed is rough.
