Regular, bichromatic and random waves on co-linear currents

Experiments have been performed for regular, bichromatic and random waves propagating with and against a turbulent current in a laboratory flume over a two-dimensional slatted bed roughness and over a smooth bed. Measurements of mean, wave-induced and turbulent velocities, instantaneous bed shear stresses, wave lengths and wave heights have been presented. The results provide an insight into the complex behaviour of combined wavecurrent flows and will be of use in the validation of wave-current models. INTRODUCTION An understanding of the behaviour of combined wave-current flows remains an essential requirement for those interested in coastal hydrodynamics and sediment transport. Despite continuing interest in this subject over many years, there remain relatively few relevant sets of data in the literature. The validation of most theoretical models relies upon the results from flume tests on regular waves by Bakker and van Doom (1978), Kemp and Simons (1982, 1983), and Klopman (1994). This paper describes a series of experiments performed in a laboratory flume with the aim of providing new kinematic and bed shear stress data against which to assess existing wavecurrent models and to inform new approaches under development in a parallel project. FLUME The tests were performed in the same facility as used by Kemp and Simons (1982, 1983). For those earlier wave-current tests, a single bottom-hinged wave maker produced waves at one end, a permeable beach absorbed waves at the other end, and currents could be introduced at either end to allow following or opposing wave-current Department of Civil & Environmental Engineering, University College London, Gower Street, LONDON WC1E 6BT, United Kingdom: r.r.simons@ucl.ac.uk