LAUSR

Abstract Preferential concentration is a phenomenon where particles in turbulent flow concentrate in regions of low vorticity and high strain rate, forming clusters. This phenomenon is prevalent in nature and various industrial environments. Previous measurement systems for detecting this phenomenon have been based mostly on discrete images, and is relatively slow because of the image post processing involved. We have developed a new fast-response continuous measurement system comprised of a photomultiplier tube (PMT), custom-designed lens tube, and a continuous wave Nd:YAG laser. Experiments were conducted in a chamber that creates homogeneous isotropic turbulence with no mean flow. Image-based Voronoi analysis and box counting analysis from a high-speed camera were compared against the new PMT-based method for three Stokes number cases of near 0, 2.2, and 10. As the Stokes number was varied, the new technique showed similar results compared to the conventional camera-based methods.