Experimental study on spatial variation of mass transport induced by surface waves generated in a finite-depth laboratory flume

Abstract

The aim of laboratory experiments conducted in a wave flume is to confirm that wave-induced mass transport varies along the way of propagation of regular mechanically generated waves in water of finite depth. This effect is attributed to the interactions between primary waves generated in the flume and associated free waves. Measurements of wave kinematics in several locations along the flume are performed to evaluate mass transport. Wave gauges and the particle image velocimetry technique are employed, respectively, to provide information on the evolution of the oscillating water surface and the wave velocity field under regular waves. Laboratory data are compared with numerical predictions of the derived nonlinear wavemaker model based on a pseudo-spectral approach. The experimental data exhibit good agreement with the numerical results with respect to particle trajectories and mass transport for nonlinear transitional and shallow water waves. Numerical and experimental investigations confirm that free-surface oscillatory motion and particle kinematics are affected by second-order free waves, which modify the characteristics of laboratory waves, especially in a strongly-nonlinear shallow water regime. Moreover, the present study gives valuable insight into the effects of the interaction between two independent waves on wave-induced mass transport, which highlights the need of including nonlinear energy transfers between higher harmonics for the reliable estimation of wave processes in ocean circulation models.