5-MHz Particle Image Velocimetry in small-scale Multiphase Blasts
Description
Experiments were designed to visualize the near field of a commercial detonator blast illuminated by the laser. The Nd:YAG burst-mode laser (532nm) and Shimadzu HPV-X2 camera are leveraged to obtain time-resolved (5 megahertz) PIV measurements from the laser illuminated images. Instead of seeding the flow, the particle field produced by the multiphase blast itself is used to track the flow.
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Steps to reproduce
A Nd:YAG burst-mode laser and Shimadzu HPV-X2 camera are leveraged to obtain time-resolved (5 megahertz) particle image velocimetry (PIV) measurements at of an RP-80 (167-9964) detonator. The detonation-breakout surface was 0.29 mm below the the center of the field-of-view (24 × 38.5 mm2). The 532 nm laser beam (1 mJ/pulse) was then split into two beams using a 50/50 beam splitter to illuminate the blast from both sides in an optically accessible explosive chamber. Instead of seeding the flow, the particle field produced by the multiphase blast itself is used to track the flow. The resulting laser-illuminated images were masked images and used to calculate the velocity fields. The masks were generated from the raw images utilizing cumulative stacked frames and the global maximum binarization function from MATLAB. Velocity vectors were calculated with LaVision’s (Davis 8.4.0.36294) sequential time-series cross-correlation algorithm. This algorithm used a 4× multi-pass configuration with decreasing size, beginning with a 64×64 pixel square window and refining the results with three high-accuracy passes of an auto-shape 16×16 pixel window. Postprocessing smoothing was performed using a median filter and outlier rejection; the remove & replace routine was used for vectors with low accuracy (correlation value < 0.7).