PowderSim is a calculation tool that combines a discrete-element method (DEM) module, including calibrated interparticle- interaction relationships, with a mesh-free, continuum, SPH (smoothed-particle hydrodynamics) based module that utilizes enhanced, calibrated, constitutive models capable of mimicking both large deformations and the flow behavior of regolith simulants and lunar regolith under conditions anticipated during in situ resource utilization (ISRU) operations.

The major innovation introduced in PowderSim is to use a mesh-free method (SPH-based) with a calibrated and slightly modified critical-state soil mechanics constitutive model to extend the ability of the simulation tool to also address fullscale engineering systems in the continuum sense. The PowderSim software maintains the ability to address particlescale problems, like size segregation, in selected regions with a traditional DEM module, which has improved contact physics and electrostatic interaction models.

PowderSim provides answers with comprehensive cohesivecontact models and a new charge-spot model for electrostatic forces arising from localized charge patches on the surfaces and in the interiors of individual particles. For systems that are too large to be simulated with a discrete element approach, PowderSim incorporates a continuum-based SPH module, which when considering the addition of a calibrated, cohesive, constitutive model (Lunar Regolith Constitutive Model (LRCM)), is a novel use of mesh-free methods. Because of the discrete and continuum methods implemented in the same framework, the software can capture dynamic particulate material behavior at a variety of spatial scales from the coarse-grain scale (DEM) to the bulk scale (SPH). The DEM capability also supports clustering, which allows it to capture a rich variety of shape detail. Advanced contact models and charge spots capture many effects of contact plasticity and hysteresis, roughness, adhesion, and electrostatic interaction of particles. The SPH capability for bulk material behavior uses the LRCM to capture the critical-state behavior of cohesive lunar regolith.

This work was done by Scott Johnson, Otis Walton, and Randolph Settgast of Grainflow Dynamics for Glenn Research Center.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steven Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. LEW-18801-1

NASA Tech Briefs Magazine

This article first appeared in the January, 2013 issue of NASA Tech Briefs Magazine.

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