Judy Yang and her lab group

Yang Seeks Fine-grained Understanding of Sediment Transport

Judy Yang, Assistant Professor in CEGE, received an NSF Grant in excess of $300,000 for her project “Collaborative Research: Grain to Channel Scale Experimental and Numerical Investigation of Cohesive Sediment Transport.”

Each year, erosion leads to billions of dollars in lost property and large areas of lost habitat. Restoration of these eroded areas often involves importing dirt, sand, or other sediment. The final success of restoration efforts depends on the ability of the area to retain the imported sediment. Thus, designing erosion restoration projects requires a fine-grained understanding of how soil and sediment are affected by the movement of water.

Environmental and Water Resource Engineers have established methods for predicting the transport of non-cohesive sediment, such as sand and gravel. However, it remains difficult to predict the transport of cohesive sediment, which consists of very fine particles because they tend to stick together and form aggregates. These aggregates greatly change the effective size of the particles and their interaction with the flow.

Clay and mud are ubiquitous in aquatic ecosystems, making it very important to understand how fine cohesive particles form aggregates, and how the process of aggregation controls the transport of sediment in water.

Judy Yang’s project will work to develop understanding and predictive equations for cohesive sediment transport. Yang’s study will directly address the key challenges that currently inhibit understanding of these processes, namely those related to the multiple scales (micro- to mezzo-) and multiple physical fields (fluid dynamics, aggregation, structural deformation, etc.) involved in cohesive sediment transport dynamics. The results of Yang’s study will help improve designs for restoration projects to mitigate loss from erosion.

Additional components of this project include training for next-generation environmental scientists and engineers at undergraduate, graduate, and postdoctoral levels. For even broader outreach, videos about erosion will be created and disseminated to the public, along with demonstration experiments designed to raise K-12 students’ interest in environmental science.

Some of the specific approaches include nano- to micro- scale imaging, coarse-grained molecular dynamics (CGMD) simulations, micro- to mesoscale millifluidic experiments, computational fluid dynamics (CFD) simulations, channel-scale experiments in flumes and in the SAFL outdoor stream, and CFD simulations. These experiments at various scales and in multiple fields of physics will help us understand the critical impacts of clay aggregation on channel-scale cohesive sediment transport.