Role of gravity on granular drag (Granular Drag)

abstract

The drag force acting on an object moving inside granular materials with and without the influence of gravity shall be investigated via a hybrid experiment to be conducted at the Bremen drop tower. Under gravitational acceleration (1g), the drag force of a drop capsule falling into Styrofoam particles - a granular damper optimized to decelerate the capsule - will be measured by embedded sensors and analyzed in comparison to small-scaled lab experiments and numerical simulations. Under micro-gravity (µg), parallel experiments with projectiles of various mass and shapes impacting into Styrofoam particles of various packing densities will be conducted in the payload area of the falling capsule using the same type of sensing technique and high speed imaging. The goal of this project is to evaluate the role of gravity in existing empirical laws for granular drag, considering granular materials as continuum. From a fundamental perspective, this investigation will shed light on a general understanding of drag force in complex fluids. From an application perspective, the outcome of this project can help in optimizing the efficiency of the granular dampers at the drop tower as well as other facilities, in better controlled landing and exploring of spacecraft on an astronomic object due to the ubiquity of granular materials in space.

experiment year: 2019
number of drops: 8