AI Insight
Researchers investigated how granular materials flow through constrictions across different gravitational environments, identifying the granular Bond number (ratio of particle cohesion to gravity) as the key parameter for predicting clogging behavior. Using drop tower experiments simulating Moon and Mars gravity with extraterrestrial soil simulants, they found that clogging probability increases substantially in reduced gravity, contrary to some previous predictions. Their unified scaling framework allows Earth-based measurements to predict granular flow behavior in low-gravity environments by rescaling data according to the Bond number.
Why it matters
This work provides critical predictions for space missions requiring granular material handling, such as regolith processing on the Moon, Mars, and asteroids. The unified framework enables engineers to design reliable hoppers, conveyors, and material handling systems for extraterrestrial environments based on Earth-based testing.
Understand the Science
arXiv:2506.18771v3 Announce Type: replace-cross
Abstract: Lacking a universal law for granular flows across gravitational environments, fundamental processes such as hopper discharge remain vulnerable to failure in low gravity environments. A central challenge is clogging, the spontaneous arrest of flow through a constriction; yet previous studies report contradictory results on its dependence on gravitational acceleration. We identify the granular Bond number as the missing control parameter, defined as the ratio of intrinsic cohesive interactions among particles to gravity. Based on an in-bulk measurement of this quantity, we propose to rescale Earth-measured data for predicting granular behavior in low gravity. We present experiments of granular flow through an orifice under true reduced gravity (Moon and Mars), using an active drop tower, and extraterrestrial soil simulants as model cohesive materials. Our experiments reveal substantially increases in clogging probability, contrary to previously predicted, which depends on the properties of the material itself. When rescaled by the Bond number, seemingly conflicting results can be explained and collapse into a unified state diagram, predicting clogging across materials and gravitational accelerations. This establishes a general framework for the cohesion-to-gravity competition. Future space missions to the Moon, Mars, and asteroids will rely on such predictions of granular behavior in low gravity.
Source: Granular clogging across gravities: a unified scaling