Pulsatile pipe flow experiment to study particle-fluid interactions using Lagrangian flow measurements

Simultaneously tracking particle and fluid motion is notoriously challenging yet essential for experimentally elucidating their interaction dynamics. In this study, we present comprehensive three-dimensional measurements of particle-laden flow in a novel pipe flow experiment. The experimental setup features a pipe with a 28 mm diameter and a length of up to 20 m, capable of generating both steady and pulsatile flows using an accurately controlled piston-driven system. The Reynolds number range of 50-7400 allows exploration from laminar to turbulent flow regimes. Furthermore, the pulsatile flow capability enables investigations into the effects of driving frequency, amplitude, and waveform. The system's suitability for studying particle-laden flows with complex physiological pulsation waveforms is demonstrated in detail. Measurements employing three-dimensional Lagrangian particle tracking, based on the Shake-The-Box algorithm, illustrate the unprecedented potential of this method for in-depth analysis of spatiotemporally complex flows, as exemplified by particle-laden pulsatile pipe flow. For the first time, the flow field was tracked simultaneously with the dynamics of a hydrogel particle, capturing its position, velocity, rotational axis, and angular velocity. Such rich datasets can validate four-way coupling in multiphase flow simulations and provide critical insights into turbulence transitions induced by particles. Complementary measurement techniques are also presented, including an efficient single-camera setup to detect particle migration and high-resolution differential pressure measurements (with accuracy in the range of a few Pascals) to identify the onset of turbulence.