Experimental investigation of fluid-particle oscillating flows

Non intrusive optical methods are used to investigate the velocity flow field over rippled beds in an oscillating box. Visualizations and measurements are compared between beds consisting of solid particles with different size and density: sand, glass particles and marble powder. The box oscillation gives rise to bed ripples only when the frequency of oscillation is close to one of the natural frequencies of the system and the amplitude of oscillation is larger than a threshold value (which depends on the bed particles, the water height in the box and the frequency of oscillation). Glass particles are those which display the larger bed ripples due to their lower density and their spherical shape. Close to the ripple crest strong solid particle suspensions and fluid ejections are observed when the free-surface wave is passing over.