Ultrafast X-ray study of dense-liquid-jet flow dynamics using structure-tracking velocimetry

High-speed liquid jets and sprays are complex multiphase flow phenomena with many important industrial applications1, 2. Great efforts have been devoted to understand their dynamics since the pioneering work of Rayleigh on low-speed jets3, 4. Attempts to use conventional laser optical techniques to provide information about the internal structure of high-speed jets have been unsuccessful owing to the multiple scattering by droplets and interfaces, and the high density of the jet near the nozzle exit5. Focused-X-ray-beam absorption measurements could provide only average quantitative density distributions using repeated imaging6. Here, we report a novel approach on the basis of ultrafast synchrotron-X-ray full-field phase-contrast imaging7. As illustrated in our case study, this technique reveals, for the first time, instantaneous velocity and internal structure of optically dense sprays with a combined unprecedented spatial and time resolution. This technique has tremendous potential for the study of transient phenomenon dynamics