An assessment of k–ε and k–l turbulence models for a wide range of oscillatory rough bed flows

The k–ε and k–l eddy viscosity turbulence models are now used extensively in environmental flow modelling. In the present work computations for oscillatory flows are examined over a broader range of experimental parameters than considered previously. Comparisons are made with field measurements and laboratory data, including new measurements reported here for the first time. It is confirmed that the bed friction velocity and mean flow profiles are, in general, adequately predicted by both models (the k–ε model is, however, somewhat more accurate than the k–l formulation). Reynolds shear stress, turbulent kinetic energy, and eddy viscosity are less well predicted, although the k–ε model again gives more accurate results than the k–l model. An attempt has been made to assess the uncertainty in the experimental data for Reynolds stress and eddy viscosity: it is found that the k–ε model computations for both quantities more frequently lie within the estimated uncertainty bounds. Those bounds are nonetheless wide, emphasizing the need for improved experimental resolution of rough bed flows. Such an improvement would assist in the evaluation of proposed refinements to commonly used turbulence models such as those under investigation here and, indeed, to greater reliability in the development and assessment of more sophisticated schemes.