Verification of acoustic streaming measurement accuracy via particle image velocimetry considering the interrogation window aspect ratio

Abstract

This study measured Rayleigh and Schlichting streaming velocities via particle image velocimetry (PIV) in a standing wave field. Emphasis was placed on balancing high measurement accuracy with high spatial resolution in the boundary layer region. We aimed to achieve high resolution and enhanced measurement accuracy, typically a trade-off, by significantly increasing the aspect ratio of the interrogation window in the flow direction during PIV post-processing. The experiment operated under conditions with a duct axis streaming velocity of approximately 8.3×10−3 m/s in the measurement area. Increasing the aspect ratio from 1 to 21 reduced the standard deviation across the entire radial direction, which served as the accuracy index, from 8.05×10−3 m/s to 5.23×10−4 m/s (94% reduction). Additionally, the method's validity was confirmed through synthetic images with particles of known velocity. This verification demonstrated a decrease in the standard deviation comparable to the experimental images (97% reduction), aligning the analyzed velocity's radial distribution with the known streaming velocity distribution.