Experimental Investigation of Micrometric Droplets and Artificial Particles

by Johannes Milan Güttler
Doctoral thesis
Date of Examination:2021-07-13
Date of issue:2022-04-28
Advisor:Prof. Dr. Eberhard Bodenschatz
Referee:Prof. Dr. Eberhard Bodenschatz
Referee:Prof. Dr. Martin Rein
Referee:Prof. Dr. Jens Niemeyer
Referee:Prof. Dr. Dr. Andreas Dillmann
Referee:Dr. David Zwicker
Referee: Prof. Dr. Apl. Ulrich Apl. Parlitz
Persistent Address: http://dx.doi.org/10.53846/goediss-9205

 

 

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Abstract

English

Clouds and atmospheric particles (e.g. ice crystals, smoke, dust or pollen) heavily influence Earth's energy budget and contribute to the largest uncertainties in climate prediction models. Their treatment involves a huge variety of scales, from sub-micrometer particles that act as cloud condensation nuclei (CCN) to turbulent mixing and entrainment processes, up to coherent atmospheric flows that can span tens to thousands of kilometers. This causes challenges for both simulations and theory as most climate models cannot resolve scale differences on that order. Combining simulations and theory with in situ and laboratory work, however, can enhance our understanding significantly. Different approaches exist, ranging from satellite observations to airborne, ship-based and field-site studies to controlled experiments. In this work, micrometer-sized droplets and particles are created and studied in a laboratory setting. For this, several apparatus and software were designed and tested: 1) A droplet generator able to produce droplets with diameters smaller 100 micron, 2) A settling chamber to study ellipsoidal particles within the intermediate regime 3) Single- and multi-camera tracking codes to determine particle trajectories and orientations for non-spherical particles. Together, these methods compose a first step in determining particle drag, terminal velocities and particle relaxation times for so far unexplored particle shapes and density ratios.
Keywords: atmosphere; particle; non-spherical; irregular; density ratio; relaxation time; turbulence; drag; rotation; orientation; settling; terminal velocity
 
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