  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.
