Streamwise Turbulence Modulation in Non-Uniform Open-Channel Clay Suspension Flows

de Vet, M. G.W.; Fernández, R.; Baas, J. H.; McCaffrey, W. D.; Dorrell, R. M.

Abstract

Cohesive sediment particles are ubiquitous in environmental flows. The cohesive properties of clay promote the formation of clay flocs and gels and relatively small suspended clay concentrations can enhance or suppress turbulence in a flow. Furthermore, flows are naturally non-uniform, varying in space and time, yet the dynamics of non-uniform open-channel clay suspension flows is poorly understood. For the first time, the adaptation time and length scales of non-uniform clay suspension flows were quantified using novel experiments with spatially varying but temporally uniform flow. Different levels of turbulence enhancement and attenuation were identified as the flow decelerates or accelerates. Results highlight that decelerating clay suspension flows crucially have a longer adaptation time than accelerating clay suspension flows. This is explained by the longer timescale required for the formation of bonds between cohesive particles in turbulence attenuated flows after deceleration than the rapid breakdown of bonds in turbulent flows after acceleration of clay suspension flows. This hysteresis is more pronounced for higher concentration decelerating flows that pass through a larger variety of clay flow types of turbulence enhancement and attenuation. These different adaptation time scales and associated clay flow type transitions are likely to affect clay flow dynamics in a variety of fluvial and submarine settings.

Citation

de Vet, M. G., Fernández, R., Baas, J. H., McCaffrey, W. D., & Dorrell, R. M. (2023). Streamwise Turbulence Modulation in Non-Uniform Open-Channel Clay Suspension Flows. Journal of Geophysical Research: Earth Surface, 128(8), Article e2022JF006781. https://doi.org/10.1029/2022JF006781

• Journal Article Type: Article
• Acceptance Date: Jul 19, 2023
• Online Publication Date: Jul 26, 2023
• Publication Date: Aug 1, 2023
• Deposit Date: Feb 19, 2024
• Publicly Available Date: Feb 20, 2024
• Journal: Journal of Geophysical Research: Earth Surface
• Print ISSN: 2169-9011
• Electronic ISSN: 2169-9011
• Publisher: American Geophysical Union
• Peer Reviewed: Peer Reviewed
• Volume: 128
• Issue: 8
• Article Number: e2022JF006781
• DOI: https://doi.org/10.1029/2022JF006781
• Keywords: Turbulence modulation; Cohesive sediment; Non-uniform flow; Transitional flow
• Public URL: https://hull-repository.worktribe.com/output/4373005