Image-processing-based ultrasonic velocimetry development with high applicability to flows in microparticle dispersion

Abstract

This study presents the development of a novel methodology, image-processing-based ultrasonic velocimetry (IPUV). For evaluating flow velocity, we present a new perspective utilizing image processing for spatiotemporal echo images instead of conventional ultrasonic analysis methods such as pulse compression and quadrature detection. In addition to traditional tracer particle size O(100 μm), IPUV has a high applicability for measuring the velocity of microparticle dispersion of the particle size O(1 μm) and dilute concentration O(0.001 wt.%). Velocimetry utilizing microparticles has significant merit: Velocity measurements can be conducted under conditions with less influence on the flow and higher traceability to fluid flow than the size conventionally used as a tracer particle. The accuracy and effectiveness of velocity analysis based on the IPUV principle are verified numerically and experimentally. In the experiments, IPUV was applied to Couette flow and stirring flow. In the former, the validity of the velocity profiling by IPUV was confirmed compared to the theoretical profiles of Couette flow. In the latter, IPUV measured velocity profiles in the stirring flows with different dispersions [spherical particle O(100 μm) and mica O(1 μm)]. Differences in the ability of dispersed particles to follow turbulent fluctuations in stirring water flow appeared in the frequency spectrum of IPUV velocity profiles.