Modelling of velocity and turbulence fields around and within low-crested rubble-mound breakwaters

A description of the progress achieved within DELOS (environmental DEsign of LOw-crested coastal defence Structures) EU project in the modelling of wave interaction with low-crested structures (LCS) is presented in this paper. Emphasis is put on the description of the near-field flow, especially the velocity and turbulence distribution around and inside LCS, as required by other researchers in the project. Two-dimensional (VARANS) and three-dimensional (LES) numerical modelling has been considered. The two-dimensional model has been extensively validated with DELOS laboratory data as shown in Garcia et al. [Garcia, N., Lara, J.L., Losada, I.J., 2004. 2-D Numerical analysis of near-field flow at low-crested breakwaters. Coastal Engineering, ELSEVIER, 51 (10) 991-1020.]. A system of flow recirculation is included in both the experimental and numerical set-ups for a correct description of the 2DV velocity field in the vicinity of the structure. Further validation is presented in this paper. Laboratory tests on two values of crest width have been simulated in order to analyse relevant near-field flow features related to a variation of the geometric configuration of the structure. The width of the breakwater crest is seen to significantly influence the wave breaking-induced flow pattern at the structure. Magnitudes such as turbulent kinetic energy (TKE), TKE dissipation rate, shear stresses and Reynolds stresses are computed around and inside the breakwater. The three-dimensional model numerical results are compared with results of wave basin experiments, showing a good agreement for instantaneous free surface. Numerical results of the flow over the breakwater and around the breakwater head are also presented.