20-EPN-053: Investigation of the electrical properties of volcanic ash
May 16, 2023

20-EPN-053: Investigation of the electrical properties of volcanic ash

Visit by Eduardo Rossi, University of Geneva (Switzerland) to TA2.4 Planetary Environment Facilities (PEF), AU (Denmark)
Dates of visit: 11-17 June 2022

The set of experiments within the 20-EPN-053 project represents a preliminary step towards the characterisation of the electrical properties of volcanic ash in a collaboration between the University of Geneva and the Aarhus University. This topic is fundamental to better understand aggregates formation in a volcanic eruption and improve model forecasting.

The main setup consists of a horizontal wind tunnel where a recirculating flow allows volcanic ash of different sizes (e.g. from 1 μm to 500 μm, sieved in intervals of half-phi on the Krumbein scale) and compositions (e.g. from basaltic to andesitic) to be resuspended and collide together. Single particles and aggregates are filmed during their motion in the wind tunnel by means of a High Speed Camera (HSC) placed crosswise to the main flow direction. In addition to this, a set of four Optical Particle Counters (OPCs) are located at different heights downwind to the flow (i.e. 5 cm, 10 cm, 25 cm, 50 cm) with the goal of capturing differences in particle population for very fine ash (i.e. <40μm) due to electrostatic phenomena.

The primary goal is to detected particle trajectories that will be later used to quantify the bulk charge carried by single particles by means of an inversion of the equation of motion. The secondary goal is to understand if OPCs can be used combined with the wind tunnel facility to reveal a change in particle population on the recorded histograms that can be associated with aggregation processes due to the electrostatic force.

Read the full scientific report, with kind permission from Eduardo Rossi.