PRIME: Unresolved fluid mechanics at liquid/gas interfaces for PRIMary brEakup of atomizing sprays

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Efficient spray atomization plays a critical role within society, ranging from effective medical treatment to cleaner propulsion systems. Primary breakup - the process of disintegrating a liquid stream into large (primary) drops - is the consequential first step of atomization, but is also the least understood for atomizing sprays. This long-standing problem exists due to a lack of experimental tools that can measure the fundamental fluid dynamics that govern the primary breakup processes at liquid-gas interfaces (LGI) at the core of the spray. PRIME is uniquely designed to address this problem. We have developed a unique set of advanced diagnostic tools that provide the exclusive capability to measure fluid velocity and acceleration at LGIs of the liquid jet and primary drops. These tools are a unique combination of pulse-burst Ballistic Imaging combined with wavelet-based Optical Flow (wOF). In PRIME, we establish our proof-of-concept tools, and develop wOF for original applications with two-photon laser induced fluorescence, to provide ground-breaking measurements that help resolve unanswered questions of primary breakup. Two spray facilities will be developed in PRIME, which provide a unique platform to apply our diagnostics for new fundamental knowledge for a range of sprays from basic to technically-relevant complex sprays. These facilities will include custom-built transparent nozzles to perform imaging measurements inside the spray nozzle. Advanced diagnostics will be combined with a suite of established imaging diagnostics (shadowgraphy, schlieren, micro-PIV) to correlate the primary breakup flow dynamics with its corresponding breakup genesis occurring inside the spray nozzle. PRIME will provide substantial breakthroughs in knowledge, and will generate a comprehensive spray database designed for the development and validation of computational models for the wider spray community. As such, PRIME is intended for long term success.