This paper describes a study of the hydrodynamics in the swash zone using an impermeable concrete beach in a laboratory flume. Analysis was made of the measurements achieved using level wave gauges and a laser Doppler velocimeter. From these measurements we could derive the mean motion and turbulence characteristics along the main flow direction in three vertical sections of the swash zone. Fluid velocity seems almost uniform along the vertical, especially during the up-rush; the behaviour of turbulence dynamics is a mixture of free turbulence generated during wave breaking and convected by the mean motion, and wall turbulence. This work covers analysis in the time and frequency domain and the turbulent properties of the flow field derived from our measurements are discussed.
Coastal region management is becoming increasingly important and requires a detailed knowledge of the numerous phenomena that occur near the coast. There are several problems to solve, connected with sediment transport, pollutant dynamics, currents and waves near harbours and beaches; thus many numerical models have been developed and successfully applied. The first models, based on a linear approach, have led to a better understanding of the dynamics of sea waves, solving wave propagation and wave-structure interaction in deep and shallow water. Their conceptual and computational simplicity leads to some engineering applications and indeed these models are successfully used, even though it is well known that there is a fair amount of non-linear behaviour. For the most complex cases, the results of linear models are used as a first approximation to address more detailed approaches. The dream of numerical researchers is to integrate the full Navier- Stokes equations but this is not feasible, due to the computational limitations at a high Reynolds number even in limited integration domains.