Spherical Inertial Sensor for Measuring Particle-Scale Interactions in Geomorphic Flows with Full Kinematic Equivalence

Assessing particle-scale interactions and transport phenomena is essential yet complex within geophysical flows found in both natural and artificial settings. This research introduces the design, validation, and calibration of a spherical inertial sensor particle meticulously engineered to achieve full kinematic equivalence with a solid sphere. By employing Micro-Electro-Mechanical Systems Inertial Measurement Unit (MEMS-IMU) technology, this low cost 40 mm particle can measure triaxial acceleration up to ±16g and triaxial angular velocity up to ±2000°/s, operating at a high sampling rate of 1000 Hz over a duration of one hour. The sensor particle possesses a dual-layered spherical configuration deliberately crafted to ensure alignment in shape, density, center of mass, moment of inertia, and elastic modulus with that of a solid sphere. Its performance is rigorously assessed, validated, and calibrated through a series of physical experiments. Furthermore, a data enhancement technique grounded in lubrication theory is invented to mitigate technical challenges associated with accelerometer saturation and temporal resolution. This method enables our sensor particle to accurately capture particle collision processes within liquid environment, which proves challenging with conventional approaches. This investigation offers a foundational instrument for large-scale particle motion studies, such as those related to debris flows, facilitating, for the first time, the precise measurement of the dynamic behavior of individual particles within a substantial ensemble.