Enhancing jet breakup through the manipulation of the fluid interface using fluid-transmitted acoustic waves

Droplet production from fluid jets is useful in many applications, from 3-D printing to fuel combustion in aircraft engines. Here, we incorporate a 7 MHz device producing ultrasound transmitted in the fluid jet to aid its controlled breakup. We demonstrate the ability to significantly reduce the distance to break up using a mechanism not reported before that is substantially different than traditional, low-frequency oscillation-driven instability mechanisms. Instead, here we find the nonuniform acoustic pressure distribution present along the fluid interface produced by the transmitted ultrasound is sufficiently powerful to drive jet breakup. We demonstrate this phenomenon at flow rates and with fluids particularly relevant to fuel injection in aircraft engines.