Towards probing velocity distributions in dense granular matter: Utilizing Fiber Bragg Gratings

TL;DR

This paper introduces a novel Fiber Bragg Grating sensor technique for measuring particle velocities in dense granular matter, overcoming limitations of traditional particle tracking at high densities, and validates its accuracy against conventional methods.

Contribution

The paper presents a new in situ measurement method using FBG sensors to determine velocity distributions in dense granular systems, extending experimental capabilities.

Findings

FBG sensors reliably detect particle impact velocities.

Velocity distributions obtained match traditional particle tracking results.

Method effective at high particle densities.

Abstract

Granular gases are commonly characterized through their velocity distribution, which provides access to the granular temperature. In experiments, velocity distributions are typically obtained by particle tracking, which however becomes limited at moderate and high particle densities. As a way forward, we propose a new technique for measuring particle velocities in situ by using a Fiber Bragg Grating (FBG) sensor, which remains applicable at significantly higher particle densities.The FBG sensor detects strain pulses induced by particle-fiber collisions, from which the velocity of the impacting particle can be derived. Applying this method to an ensemble of granular particles allows to extract its velocity distributions as we present for a granular system excited by a vibrational shaker. We validate the extracted velocity distribution against conventional particle-tracking measurements, confirming the reliability of the FBG-based technique.