Examination of turbulent flow induced by particle sedimentation by RIM-PIV

The turbulent flow induced by particles fed into water was measured using refractive index matched-particle image velocimetry (RIM-PIV). The development process of turbulent flow was examined based on PIV on a two-dimensional (2-D) plane. With respect to the measurement results of physical quantities related to the fluctuation velocity, a mottled distribution indicating a particle-scale spatial variation related to the random behavior of each particle spreads over the submerged particle area in the early stage of particle feeding. After the particle feeding was completed and energy supply ceased, the distribution gradually transitioned to a large mottled spatial distribution, showing the organized behavior of the particle cluster. Furthermore, the importance of the measurement in the depth direction and the evaluation of the interaction force between the particles and fluid were shown by examining the turbulent energy budget. In the final part of the development process of the oval circulating flow by feeding particles and its structure, the existence of a shear layer encircling the low-pressure region near the center of the circulating flow was detected.