Lagrangian particle tracking and measurements of particle rotation elucidate dynamics of pulsatile particle-laden pipe flow

Kurzfassung

Particle suspensions in pulsatile pipe flow are ubiquitous in industrial processes and physiological systems. An experimental challenge is the simultaneous three-dimensional (3D) measurement of the particle and fluid motion, which is necessary to fully characterize these types of flows. In a long pipe experiment (up to 20 m) we illuminate a pipe volume (having a diameter of D = 28 mm and a length of about 4 D) with a pulsed laser and monitor it with four high-speed cameras to elucidate the particle-flow interaction. A hexagonal prism minimizes optical distortions, and tracers are added to the liquid to track them with the Shake-The-Box (STB) algorithm. In order to produce a suspension of about 1% particle volume fraction, we add hydrogel particles with a diameter of about 0.4 D. Hydrogel particles are transparent and therefore provide ideal optical access to the fluid flow even in their vicinity. In addition, the hydrogel interface can be detected by tracers adhering to its surface. This allows us to measure the hydrogel trajectory and even the rarely measured quantities of particle rotation axis and angular velocity. The experimental setup and the calibration and measurement procedure are explained in detail.