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Published on: November 13, 2014
Low-velocity granular drag in reduced gravity.
D J Costantino1, J Bartell, K Scheidler
1Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Summary
The drag force on objects in granular materials is directly proportional to effective gravity. This relationship holds true across a wide range of effective grain weights, confirming a key physical principle.
Area of Science:
- Physics
- Materials Science
- Fluid Dynamics
Background:
- Granular materials exhibit complex flow behaviors.
- Understanding drag forces is crucial for predicting material transport and interactions.
Purpose of the Study:
- To investigate the relationship between low-velocity drag force and effective gravitational acceleration (g(eff)) in granular materials.
- To determine if the drag force scales linearly with g(eff).
Main Methods:
- Spherical granular materials saturated in fluids of varying densities were used.
- Effective gravitational acceleration (g(eff)) was systematically varied over two orders of magnitude.
- Drag force on a vertical cylinder probe was measured.
Main Results:
- The granular drag force (F(probe)) was found to be directly proportional to the effective gravitational acceleration (g(eff)).
- The relationship F(probe) = ηρ(grain)g(eff)d(probe)h(probe)² was confirmed, where η is a dimensionless constant.
- The dimensionless constant η remained consistent across four orders of magnitude of effective grain weight.
Conclusions:
- The linear dependence of granular drag on effective gravity is validated over an extensive range.
- The findings support established theoretical models for drag forces in granular media.
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