The electrifying physics of windblown sand


Wind blown sand is a damned nuisance. And not just cos it sandblasts cars, fills the atmosphere with aerosols and makes yer eyes water.

Geophysicists ain’t never been able to explain it good ‘n’ proper. Why does the average height of the sand above the ground remain constant as wind speed increases, when their models say the height should increase?

Now Jasper “Ophelia” Kok and a pal at the University of Michigan in Ann Arbor say they worked it out. Recent measurements show that windblown sand generates significant electric fields because the particles become negatively charged as they bounce along the ground (a similar effect is seen in powder handling facilities). This field gets stronger as the blowin ‘n’ puffin’ gets harder but none of the classical models take this into account.

Now Ophelia has built the first model that incorporates the effects of electric field generation and says it works mighty fine in reproducing the observed characteristics of wind blown sand. As the windspeed increases, so does the electric field. This attracts the particles towards the ground and so prevents their average height from increasing. Voila!

The model even makes a prediction: as wind speeds get even higher, the electric field should become so strong that it begins to lower the average height of the windblown sand. The pair are now on the hunt for evidence that this actually happens.

Ref: Electrostatics in Wind-blown Sand

Comments are closed.