Design, construction and validation of an instrumented particle for the Lagrangian characterization of flows: Application to gravity wave turbulence

Abstract

The design and application of an instrumented particle for the Lagrangian characterization of turbulent free-surface flows is presented in this study. This instrumented particle constitutes a local measurement device capable of measuring both its instantaneous 3D translational acceleration and angular velocity components, as well as recording them on an embarked removable memory card. A lithium-ion-polymer battery provides the instrumented particle with up to 8 h of autonomous operation. Entirely composed of commercial off-the-shelf electronic components, it features accelerometer and gyroscope sensors with a resolution of 16 bits for each individual axis, and maximum data acquisition rates of 1 and 8 kHz, respectively, as well as several user-programmable dynamic ranges. Its ABS 3D-printed body takes the form of a 36 mm diameter hollow sphere, and has a total mass of (19.6 ± 0.5) g, resulting in an effective mass density of 819 kg/m3, which can be adjusted by incorporating ballasts inside its body. Controlled experiments, carried out to calibrate and validate its performance showed good agreement when compared to reference techniques. To assess the practicality of the instrumented particle, we apply it to the statistical characterization of floater dynamics in experiments of surface wave turbulence. In this feasibility study, we focused our attention on the distribution of acceleration and angular velocity fluctuations as a function of the forcing intensity. The IP’s motion is also simultaneously registered by a 3D particle tracking velocimetry (PTV) system, for the purposes of comparison. Our results show, among other findings, that the IP is able to register the gradual departure from Gaussianity and the emergence of strongly non-Gaussian distributions for the translational acceleration fluctuations as the forcing amplitude is progressively increased. Beyond the results particular to this study case, the quality of their agreement with their PTV counterparts and with previous works reported in the literature, constitute a proof of both the feasibility and potentiality of the IP as a tool for the experimental characterization of particle dynamics in such flows.