Acoustic Measurement of Sub-Aqueous Gravity-Driven Granular Flows
Bibliographic record
Abstract
Sub-aqueous granular flows are complex non-linear processes. In the ocean, the transport of granular materials at the bed depends on near-bed flow and turbulence as well as seafloor morphology and sediment properties. However, the feedbacks between these processes are still poorly understood in part due to the difficulty of making high resolution measurements without disturbing the near-bed flow. Acoustic remote-sensing technologies present a promising approach, being capable of achieving mm-scale range resolutions using MHz frequencies. However, to correctly interpret results, the interaction of MHz frequency sound with water-submerged sand-sized sediments must be understood. The first part of this presentation focuses on measurements of the geoacoustic properties of water-saturated sediment at high frequencies: sound speed and attenuation within the sediment and the reflection coefficient at the sediment-water interface. The second part focuses on sub-aqueous gravity-driven granular flows. The granular materials - 0.40 mm sand and 0.34 mm glass beads - were released from a cofferdam in a 15-cm wide inclined channel, producing O(1) cm thick granular layers moving at O(10) cm/s speeds. Vertical velocity profiles within the moving layer were measured using pulse-coherent Doppler profilers operating at MHz frequencies. Results are compared to velocity profiles measured by a side-view camera through the chute sidewall and surface velocity profiles across the chute measured by a top-view camera. Estimates of depth-averaged solids concentration are obtained from the best-fit parameters of a theoretical viscous flow model and compared to the measured concentration based on the attenuation of sound through the moving layer. Presenter Bio Dr. Jenna Hare is a Postdoctoral Research Associate at the Center for Coastal and Ocean Mapping at the University of New Hampshire working with Dr. Tony Lyons. Her research interests lie at the intersection of the fields of physical oceanography and underwater acoustics. Dr. Hare completed her BSc (2010) in physics at Laval University in Quebec followed by her MSc (2013) and PhD (2021) in oceanography at Dalhousie University in Nova Scotia.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".