Seeing the Unheard: dynamics of thin liquid film in holographic ultrasonic field revealed by time-resolved Schlieren imaging

TL;DR

This paper introduces a novel time-resolved Schlieren imaging method to visualize and analyze the complex dynamic behaviors of thin liquid films in ultrasonic fields, revealing new flow phenomena and wave interactions.

Contribution

It presents a unique imaging approach that captures high-resolution, real-time dynamics of thin liquid films in ultrasonic fields, uncovering previously unknown flow patterns and wave interactions.

Findings

Discovery of unexpected branch flow phenomenon

Observation of diverse wave patterns including capillary and standing waves

Insights into fluid behavior for applications in acoustic levitation and bioengineering

Abstract

In this study, we introduce a unique approach that employs time-resolved Schlieren imaging to capture and visualize the dynamic changes of a thin liquid (mixture of water, soap and glycerin) film in ultrasonic wave field with high spatial and temporal resolution. By placing a soap film spanning a wire frame vertically in the path of light, we harnessed the vibrations induced by the ultrasonic waves, resulting in remarkable Schlieren imaging patterns. The investigation not only uncovers an unexpected branch flow phenomenon within the film, challenging existing assumptions, but also reveals a fascinating interplay between vortex flow and branch flow. The experiments have revealed a captivating spectrum of dynamic phenomena within the thin liquid films. The observation of small-scale capillary waves, large-scale standing waves, traveling waves, and the intricate fusion of capillary-gravity wave patterns underscores the rich complexity inherent in the interaction between the films and the holographic ultrasonic wave field. These diverse states of film dynamics provide a comprehensive understanding of the intricate interplay between various wave modes and fluid behavior, further enhancing comprehension of this fascinating phenomenon. The ability to visualize the pressure field opens up new avenues for optimizing acoustic levitation techniques, investigating particle behavior, and exploring potential applications in materials science and bioengineering.