2026 CSDMS meeting-018: Difference between revisions

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|CSDMS meeting abstract title=Measurement of turbulent pressure fluctuations to inform plucking and entrainment thresholds
|CSDMS meeting abstract title=Measurement of turbulent pressure fluctuations to inform plucking and entrainment thresholds
|Working_group_member_WG_FRG=Terrestrial Working Group
|Working_group_member_WG_FRG=Terrestrial Working Group
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{{CSDMS meeting authors template
|CSDMS meeting coauthor first name abstract=Elowyn
|CSDMS meeting coauthor last name abstract=Yager
|CSDMS meeting coauthor institute / Organization=University of Idaho Center for Ecohydraulics Research
|CSDMS meeting coauthor town-city=Boise
|CSDMS meeting coauthor country=United States
|State=Idaho
|CSDMS meeting coauthor email address=eyager@uidaho.edu
}}
{{CSDMS meeting authors template
|CSDMS meeting coauthor first name abstract=Aaron
|CSDMS meeting coauthor last name abstract=Hurst
|CSDMS meeting coauthor institute / Organization=University of Colorado Boulder
|CSDMS meeting coauthor town-city=Boulder
|CSDMS meeting coauthor country=United States
|State=Colorado
|CSDMS meeting coauthor email address=Aaron.a.hurst@gmail.com
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{{CSDMS meeting abstract template 2026
{{CSDMS meeting abstract template 2026
|CSDMS meeting abstract=The detachment of intact blocks of substrate material from channel surfaces by flow hydraulics (“plucking”) is a key mechanism driving erosion in both natural and man-made channels. Despite its role in knickpoint migration and channel boundary adjustment, the physical processes controlling block motion remain poorly constrained. In particular, we lack measurements of the instantaneous turbulent pressure field and its interaction with block geometry and fracture networks at the onset of motion. Turbulent fluctuations contribute to the forces acting on objects exposed to flows and may act to initiate motion even when bulk flow metrics remain steady. This project directly measures turbulent pressure fluctuations acting on a simulated bedrock block at a downstream-facing step in subcritical, critical, and supercritical flows to quantify the forces contributing to fluvial plucking. Laboratory flume experiments employ a “bedrock” cube instrumented with 66 pressure transducers and two accelerometers, enabling simultaneous measurement of instantaneous pressures and block motion. Block protrusion (−20 to +20 mm) and fracture (joint) width (0–100 mm) are systematically varied to quantify their effects on the lift and drag forces and the sequence of block motion, including initial lift, rotation, and translation. I use planar particle image velocimetry (PIV) to resolve the near-bed velocity field and shear stress acting on the block top. The resulting dataset will provide new mechanistic insights into how flow turbulence and fracture geometry control block entrainment which may be applied to existing erosional frameworks and models of bedrock plucking such as the Hurst 1D erosion (H1DE) model.
|CSDMS meeting abstract=The entrainment of bedrock blocks by flow hydraulics (“plucking”) is a key mechanism driving erosion in both natural and man-made channels. Despite its role in knickpoint migration and bedrock incision, the physical processes controlling block motion remain poorly constrained. In particular, we lack an understanding of how the instantaneous turbulent pressure field around the block contributes to its motion. Turbulent fluctuations may act to initiate motion even when time-averaged fluid forces are below block resisting forces. To quantify the forces contributing to fluvial plucking, we measure turbulent pressure fluctuations acting on a simulated bedrock block at a downstream-facing step in a laboratory flume for subcritical, critical, and supercritical flows. The block is instrumented with 66 pressure transducers and two accelerometers, enabling simultaneous measurement of instantaneous pressures and block motion. Block protrusion (−20 to +20 mm) and fracture (joint) width (0–100 mm) are systematically varied to quantify their effects on instantaneous lift and drag forces. We also use planar particle image velocimetry (PIV) to resolve the near-bed velocity field and shear stress acting on the block top. The resulting dataset will provide new mechanistic insights into how flow turbulence and fracture geometry control block entrainment, which may be applied to existing erosional frameworks and models of bedrock plucking.
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Latest revision as of 11:07, 12 February 2026


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Measurement of turbulent pressure fluctuations to inform plucking and entrainment thresholds


Nicholas Colaianne, (he/him),University of Idaho Center for Ecohydraulics Research Boise Idaho, United States. cola8842@vandals.uidaho.edu
Elowyn Yager, University of Idaho Center for Ecohydraulics Research Boise Idaho, United States. eyager@uidaho.edu
Aaron Hurst, University of Colorado Boulder Boulder Colorado, United States. Aaron.a.hurst@gmail.com



The entrainment of bedrock blocks by flow hydraulics (“plucking”) is a key mechanism driving erosion in both natural and man-made channels. Despite its role in knickpoint migration and bedrock incision, the physical processes controlling block motion remain poorly constrained. In particular, we lack an understanding of how the instantaneous turbulent pressure field around the block contributes to its motion. Turbulent fluctuations may act to initiate motion even when time-averaged fluid forces are below block resisting forces. To quantify the forces contributing to fluvial plucking, we measure turbulent pressure fluctuations acting on a simulated bedrock block at a downstream-facing step in a laboratory flume for subcritical, critical, and supercritical flows. The block is instrumented with 66 pressure transducers and two accelerometers, enabling simultaneous measurement of instantaneous pressures and block motion. Block protrusion (−20 to +20 mm) and fracture (joint) width (0–100 mm) are systematically varied to quantify their effects on instantaneous lift and drag forces. We also use planar particle image velocimetry (PIV) to resolve the near-bed velocity field and shear stress acting on the block top. The resulting dataset will provide new mechanistic insights into how flow turbulence and fracture geometry control block entrainment, which may be applied to existing erosional frameworks and models of bedrock plucking.


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