Azimuthal edge waves are excited on a 7cm diameter water surface and imaged using a collimated white light source with long exposure time t=1s. The bottom left sequence of images shows how the azimuthal waves evolve from a concentric wave pattern. The diagram above shows a plot of scaled wave amplitude against driving frequency for concentric waves. At frequencies slightly off-resonance (by as little as 0.3 Hz) we begin to observe steady azimuthal modes (at increased driving amplitudes). These modes existed in the frequency space between concentric mode resonances; as indicated by the bands defined by the red lines in the response diagram above. The bottom sequence of images shows the progression of azimuthal wave mode number with frequency.
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