V-017: The 'Event' Horizon

The 'Event' Horizon

Dongmin Sun, Seoul National University
Hyunji Lee, Seoul National University
Hyungmin Park, Seoul National University

Here, we present a flow visualization of a radially spreading liquid sheet on a rotating disk using an event-based camera. Unlike conventional high-speed cameras, which demand complex illumination, extensive post-processing, and generate large amounts of redundant data, the event-based approach records only changes in brightness per pixel. This enabled clear visualization of liquid-sheet waves using simpler environments, with reduced data volume and minimal processing. By tuning the hyperparameters related to the event acquisition, we further enhanced wave detection compared to traditional imaging. The surface waves were qualitatively grouped into three types: concentric waves, short spirals, and long spirals. Increasing disk rotation speed led to shorter spiral wavelengths. For quantitative analysis, we introduced the wave angle as a key descriptor. Simple image processing allowed us to extract wave angles at different radii, revealing that higher rotation speeds produced smaller and less variable angles. This suggests that faster rotation encourages radial alignment of ripples and enhances overall wave stability. Overall, the present approach demonstrates that event-based cameras offer a reliable and efficient alternative to high-speed cameras for investigating spatio-temporal evolution of complex thin-film flows, providing both qualitative and quantitative insights under simplified experimental conditions.

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