Floating particles on a faraday wave
The dynamics of particles floating on a standing Faraday wave is studied experimentally. For low particle concentrations (left movie), hydrophobic light particles form very stable clusters at the antinodes due to a net force resulting from gravity and capillarity. For higher concentrations (right movie), we observe that the same particles form clusters at the nodes. The explanation lies in the collective, attractive capillary interaction among particles which counteracts the tendency of the particles to move toward the antinodes. The transition between the two regimes is studied as a function of the particle concentration Φ.
Movie 1: Antinode clusters at low Φ (top view).
Movie 2: Node clusters at high Φ (top view).
The standing Faraday wave is created by using a shaker. Hydrophobic polystyrene particles (diameter 0.6-0.8 mm) are visualized by high-speed imaging. Particle tracking method is applied to analyze the dynamics of the particles on a two dimensional wave surface. The questions we address:
- Why clustering at nodes for higher Φ?
- How does the clustering behavior change at intermediate Φ?
- How do the structural properties and the mobility of the clusters behave as a function of Φ?