Control of Fluidity via Boundary Conditions, Vibrations and Stress Fluctuations

Author Last Name: 
Vriend and Daniels
Authors: 
Nathalie M. Vriend and Karen E. Daniels
Report Type: 
CRR
Research Area: 
Powder Flow
Publication Year: 
2020
Publication Month: 
1
Country: 
United Kingdom

Research Plan & Executive Summary

In this project, we modified the boundary conditions of our existing photoelastic avalanche experiment to quantify their control on the flowability of granular materials and the extent of non-local effects in this flow. This 1-year project involved the following three work packages:

  1. Spatial evolution: explore the evolution of key parameters in the flume.
  2. Oscillating basal boundary condition: add a spatially oscillating basal boundary condition.
  3. Wall shear-stress: install an external wall shear stress sensor on the basal boundary condition.

 

Annual Report

This separate collaboration grant was funded (CRR-02-15) in 2018 - 2019 to leverage the highly-successful and cost-effective IFPRI-funded collaboration CRR-02-14, between the Daniels and Vriend lab, during 2017 - 2018. This new extension identified three different goals to modify the boundary conditions of our existing photoelastic avalanche experiment to quantify their control on the flowability of granular materials and the extent of non-local effects in this flow. The project involves the following three work packages:

  1. Spatial evolution: explore the evolution of key parameters—the fluidity field, the force and velocity fluctuations—as a function of downstream position in the flume (M1 – M2).
    • Realization: at this moment we only characterized one location, at 0.25 m from the inflow, but we have the ability to scan and measure the entire length (2m) of the experiment.
    • Aim: investigate whether the pilot-observations of non-locality at one location are consistent across the entire experiment.
  2. Oscillating basal boundary condition: quantify the effect on the non-local/local flow transition by adding a spatially oscillating basal boundary condition (M2 – M5).
    • Realization: periodically displacing the boundary insert (global rearrangement) or installing an actuator, for example an electromagnetic driver (e.g. MB Dynamics PM50A), for intermittent pulses (local rearrangement).
    • Aim: determine the mechanisms by which oscillations with different length- and time-scales influence the flowability and fluidity of the flow.
  3. Wall shear-stress: install an external wall shear stress sensor on the basal boundary condition (M4 – M7).
    • Realization: Create a custom-made transducer (beam & floating plate) or an off-the-shelf external wall shear sensor (e.g. L108 Lenterra).
    • Aim: investigate whether the flow exhibits slip, stick or sliding on the boundary, and whether stress fluctuations are measurable at the boundary.