Using NMR to Validate First-Principles Granular Flow Equations

TL;DR

This paper employs NMR techniques to experimentally validate first-principles models of granular flow in vibrofluidized and gas-fluidized beds, providing detailed measurements of density, motion, and bubble dynamics.

Contribution

It introduces NMR-based methods to directly measure granular flow properties and verifies first-principles hydrodynamic theories against experimental data.

Findings

Granular temperature profile matches theoretical predictions.

Measured bubble velocity aligns with model estimates.

NMR techniques effectively capture grain and gas dynamics.

Abstract

Nuclear magnetic resonance (NMR) experiments are described for two granular-flow systems, the vibrofluidized bed and the gas-fluidized bed. Using pulsed field gradient, magnetic resonance imaging, and hyperpolarized gas NMR, detailed information is obtained for the density and motions of both grains and interstitial gas. For the vibrofluidized bed, the granular temperature profile is measured and compared with a first-principles formulation of granular hydrodynamics. For the gas-fluidized bed, dynamic correlations in the grain density are used to measure the bubble velocity and hyperpolarized xenon gas NMR is used to measure the bubble-emulsion exchange rate. A goal of these measurements is to verify in earth gravity first-principles theories of granular flows, which then can be used to make concrete predictions for granular flows in reduced gravity.