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Granular cooling of ellipsoidal particles in microgravity
Sebastian Pitikaris1, Patricia Bartz2, Peidong Yu3,4
1Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170, Köln, Germany.
NPJ Microgravity
|April 21, 2022
Summary
Granular gas experiments on the International Space Station show particle cooling follows Haff's law. Analysis reveals particle clustering and energy distribution across translation and rotation during cooling.
Area of Science:
- Physics
- Granular Materials Science
- Space Science
Background:
- Understanding granular materials in microgravity is crucial for various applications.
- Previous studies have explored granular dynamics, but long-time cooling behavior in 3D ellipsoidal systems is less understood.
Purpose of the Study:
- To investigate the long-time cooling dynamics of a 3D granular gas composed of ellipsoids in microgravity.
- To analyze particle clustering and energy distribution across translational and rotational degrees of freedom.
Main Methods:
- Establishing a 3D granular gas of ellipsoids in the microgravity environment of the International Space Station.
- Employing two measurement methods to track particle dynamics and granular temperature over time.
- Utilizing Haff's cooling law and kinetic theory for ellipsoids for data analysis.
Main Results:
- The granular temperature evolution was measured until particle movement ceased, consistent with Haff's cooling law.
- Evidence of particle clustering was observed towards the end of the experiment using different analysis techniques.
- Comparison of translational energy dissipation per collision with the overall cooling timescale revealed insights into energy distribution.
Conclusions:
- Haff's cooling law effectively describes the observed cooling behavior of ellipsoidal granular gases in microgravity.
- Particle clustering is a notable phenomenon in the late stages of granular gas cooling.
- The study provides insights into the partitioning of energy between translational and rotational motion during granular cooling.
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