Dynamics states of particle aggregates in a forced fluid in microgravity

Pollen deposition, paleoecology, algae growth linked to water quality, plastic pollution, and storm transported sea salt in bodies of water are at first examples of particles in fluid-gas interfaces. After a certain time, when and if particles sediment, the dynamics change and the involved processes can become those of a fluid-saturated granular media. Of particular interest are externally vibrated particle-laden fluids that are used to segregate different particle sizes and materials, or to fluidize the granular material and thus improve its flow characteristics such as particulate transport. Drop tower experiments at Portland State University are performed to quantifying transient dynamics of particles in an interface in the absence of gravity. These experiments serve as a steppingstone for launching containers to space aboard the ISS to access longer periods of microgravity. Results have the potential to be an important step forward towards the understanding of aggregation of particles in a gas/fluid interface where times scales are relatively large and the effects are relatively small on Earth.