Flow attenuation due to the addition of rigid rod-like particles

Abstract

Interactions between fluid flow, in particular, turbulent flow, and solid particles are complex because many parameters control the interactions. In experiments of particle-laden turbulent flow, it is difficult to identify the scale of vortices which interacts strongly with the particles, since vortices of various scales coexist in turbulence. We, therefore, focus on the effect of the addition of solid particles to a single-scale vertical flow. More concretely, in our experiments, we use a container with a spherical cavity of 180 mm diameter. The container is filled with water and many rigid rod-like particles (the length is 12 mm and the diameter is 2 mm) are laden. We rotate the container at a constant angular velocity to create a swirling flow. This flow would be the solid-body rotation if the particles were not added. Our experiments show that the flow velocity in a central region of the cavity is drastically reduced when we add particles with a density slightly higher than that of the working fluid. We aim to explore the physical mechanism of this suppression phenomenon. For this purpose, we quantify the suppression rate by using particle tracking velocimetry (PTV) and reveal the condition when the addition of rod-like particles suppresses the swirling flow.