Impedance-matching harmonic ultrasound imaging velocimetry to visualize low particle size suspensions

This study investigates the feasibility of measuring small particle size ratio suspensions using impedance-matching harmonic imaging technology. With the advancement of ultrasonic imaging technology, echo-particle image velocimetry has been widely applied in fluid measurement. While the development of harmonic imaging technology has significantly enhanced the image quality of ultrasonic imaging, existing ultrasound methods suffer from speckle imaging when applied to dense suspensions with small particles. This limits its application in dense and small particle size suspensions. In this work, we mitigate ultrasound scattering by matching the acoustic impedance between the suspended particles and the base fluid. Pulse inversion harmonic imaging is then utilized to filter out the acoustic scatters of the suspended particles. The new approach solves the image speckle issue and enables clear visualization of flow structures in suspensions with small particle size ratios and moderate volume fractions. The proposed method successfully captures the dynamics of vortex rings in a suspension with a particle size ratio of 1:4000 and a volume fraction of 8%.