Development of a Numerical Model of Dust Charging and Transport in Dust Devils

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Development of a Numerical Model of Dust Charging
and Transport in Dust Devils
Steve Desch Arizona State University Greg
Wilson Jet Propulsion Laboratory
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• Three-dimensional grid
• Impose Rankine vortex plus wind
• Lofting of dust due to shear stress
• Aerodynamic transport of dust between grid zones

E
Z
Q
V

• Dust grains collide with ground and with each
  other, and exchange charge

• Electric field calculated everywhere.
• Does discharge occur?

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The charge on a dust grain depends on its size,
its composition, and the electric field on the
ground.
The electric field on the ground is related to
its charge, which must balance charge on all dust
particles.
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Simulated particle charges, including random
charge proportional to a
across
The magnitude and sign of charge on a particle
predicted to depend on its size.
Consistent with observations of Greeley Leach
(1978)!
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Goals and Timeline Winter 2005 Build 3-D code
that can model lofting and transport of dust in
dust devil. Spring 2006 Include detailed
microphysics of lofting into suspension /
saltation due to wind shear stress create
parallelized version of code to run on Linux
cluster. Summer 2006 Include dust charging
microphysics due to interactions with the ground
and each other create module to calculate
electric field. Fall 2006 Determine whether
Martian (or terrestrial) dust devils can trigger
electric discharges for reasonable parameters.