The proposed research is focused on the study of forces between particles that tend to cluster. The physical system is that of sentiments of quartz and clay particles. The advantage of conducting experiments at the International Space Station (ISS) is that it will be possible to separate the forces acting on the particles among short range (adhesive forces) and long range (cohesive forces), since one can observe the clustering dynamics over very long time scales without gravitational settling, which complicates the measurements when doing experiments on Earth. The quartz/clay system is commonly found in a wide variety of environment settings (rivers, lakes, oceans) and plays an important role in technological efforts related to deep sea hydrocarbon drilling and CO2 sequestration. Oil companies typically spend millions per well to fund exploratory drilling operations, and might require multiple exploration missions to find one good site. Results from this work could lead to a better computation model that will allow oil companies to find spots on the deep sea for drilling productive oil wells with higher precision.
The dynamics of cohesive sediment is governed by the interplay of gravitational, electrostatic and hydrodynamic forces. Earth-based laboratories do not allow for the investigation of cohesive and adhesive forces in isolation, as these are usually obscured by the effects of gravity and gravitational settling. Consequently, existing models for the dynamics of cohesive sediment have severe shortcomings, and reliable scaling laws for the magnitude of the inter-particle forces and the resulting flocculation rates and erodibility as functions of such parameters as grain size, surface size, grain material and water salinity are not available. This represents a serious impediment for predictive modeling efforts of a range of environmental systems in which cohesive sediment plays a central role, among them rivers, lakes, estuaries, the coastal ocean, fisheries and benthic habitats. Furthermore, given the high cost of deep-sea drilling, computational sediment transport models also play an increasingly important role in deep-water hydrocarbon exploration, where improved modeling tools will result in tangible economic benefits. The ISS microgravity laboratory will enable us to investigate cohesive and adhesive forces in isolation, without interference from gravity and the associated settling motion. In this way, the proposed research will allow us to formulate scaling laws for the dynamics of cohesive sediment as function of grain size, grain material and water salinity. The ISS experiments will to a large extent take advantage of an existing experimental apparatus that was employed in a previous investigation, so that the time and cost of preparing the experiments can be kept to a minimum. The scaling laws identified via the ISS experiments will subsequently be implemented into an existing, particle-resolving CFD code for detailed follow-up investigations of cohesive sediment dynamics under conditions with and without gravity. The proposed research will result in advanced predictive models for such environmental systems as rivers, lakes, estuaries, the coastal ocean, fisheries and benthic habitats, as well as for deep-sea hydrocarbon exploration and proposed CO2 sequestration strategies. On the educational side, the proposed research project will educate and train a postdoctoral scholar, as well as graduate, undergraduate and high school students in the broad concepts of microgravity fluid dynamics and computational model development.
