An experimental analog for the study of waving marine grass in tidal currents

Tidal currents passing through submerged vegetation mix the fluid and facilitate various environmental and ecological transport processes. This fluid-vegetation interaction, where the submerged grasses behave like those on the ground waving from wind, results from a shear instability of the surrounding flow. We devise a two-dimensional lab scale analog of the fluid-vegetation interaction using ABS plastic filaments immersed in a soap film to simulate the grass blades in a tidal flow. The array of filaments spontaneously waves in response to the flow of the soap film. Our experimental system makes direct flow measurement possible for a detailed comparison with theory.