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This Letter introduces a new, to the best of our knowledge, particle streak velocimetry technique based on decaying streaks formed by individual phosphor particles following pulsed excitation. Tin-doped phosphor particles are dispersed into flows and excited by a pulsed UV laser light sheet. Emission streaks are recorded as a result of particle motion during the persistence of luminescence (here ∼27µ s ). The two components of the flow velocity are derived from the streaks without directional ambiguity by applying to each streak a two-dimensional fit describing a linearly moving point source with a mono-exponential decaying emission. This technique can achieve high spatial resolution compared to particle image velocimetry (PIV), while also requiring much fewer computational resources than particle tracking velocimetry (PTV) at high seeding densities. The wavelength-shifted luminescence also allows rejection of reflected laser light. The approach was validated in a free jet against simultaneous PTV and PIV and then successfully applied to measure a canonical boundary layer flow.

We synthesized and characterized S c V O 4 : B i 3+ thermographic phosphor particles and demonstrated their use as a tracer for temperature imaging in a near-ambient temperature liquid flow using a single laser/camera luminescence lifetime dual-frame ratio-based method. Owing to a high temperature sensitivity of up to 6%/°C, the single-shot single-pixel temperature precision at a 400 µm spatial resolution is better than ±0.4 ∘ C (1 σ ) across the 20 to 60°C range, representing a factor >5 improvement compared to previous works using thermographic phosphors. The measurement duration is on the order of the luminescence lifetime (2 µs), which is applicable in both gas and liquid flows. This is a general temperature imaging method for sensitive measurements in dynamic fluid mechanics and thermal science applications.

We propose a point measurement technique for simultaneous gas temperature and velocity measurement based on thermographic phosphor particles dispersed in the fluid. The flow velocity is determined from the frequency of light scattered by BaMgAl10O17:Eu2+ phosphor particles traversing the fringes like in conventional laser Doppler velocimetry. Flow temperatures are derived using a two-color ratio method applied to the phosphorescence from the same particles. This combined diagnostic technique is demonstrated with a temperature precision of 4%-10% in a heated air jet during steady operation for flow temperatures up to 624 K. The technique provides correlated vector-scalar data at high spatial and temporal resolution.