Identification of weakly- to strongly-turbulent three-wave processes in a micro-scale system

TL;DR

This paper investigates capillary wave turbulence across multiple regimes in a microfluidic system, utilizing advanced holographic microscopy to identify and analyze weakly to strongly nonlinear wave behaviors and their implications.

Contribution

It introduces a set of parameters and a nonlinearity measure to identify and compare four fundamental WT regimes in a simple micro-scale system, enhancing understanding of wave turbulence.

Findings

Identification of four WT regimes in a microfluidic system

Development of a nonlinearity measure for wave analysis

Observation of strongly nonlinear WT at sub-atomization power levels

Abstract

We find capillary wave turbulence (WT) to span multiple dynamical regimes and geometries -- from weakly to strongly nonlinear WT (SWT) and from shallow to deep domains -- all within a 40uL volume millifluidic system. This study is made viable with recent advances in ultra-high-speed digital holographic microscopy, providing 10-us time and 10-nm spatial resolutions for images across the entire field of view, and encompassing a complete wave system at speeds sufficient to capture the salient wave phenomena. We provide a set of tractable parameters that identify the four fundamental WT regimes present in this simple system. A proposed nonlinearity measure permits comparative analysis while varying input conditions. This work augments current understanding of WT regimes and behaviors, and directly applies to many fields beyond fluid mechanics. For example, SWT appears upon the fluid interface at powers less than required for atomization, indicating that further study of SWT is needed to properly understand ultrasound-driven fuel spray atomization and drug and agricultural nebulization.