Impact force of non-Boussinesq gravity-current head against a circular cylinder above the seabed
Bibliographic record
Abstract
We study the impact force of the gravity-current head on a circular cylinder above the seabed for the non-Boussinesq effect using a large-eddy simulation model well validated against laboratory data. Most existing studies of the gravity current were for the slight density difference between the current and the ambient fluid, assuming the density is constant using the Boussinesq approximation. The aim of the present study, however, is about gravity current of significant density difference. We detail the coherent turbulence structure of the gravity current and the transient oscillation of the impact force on the cylinder over a range of density differences varying from (ρs−ρa)/ρa=0.02 to 2 for the elevation relative to the diameter of the cylinder E/D=0.05, 0.4 and 1.0. The velocity and vorticity field in the current show a gravity-current head separating from the primary current driven by excess pressure at the back, with a structural similarity almost independent of the density difference. The gravity-current head’s frontal and wake velocities are determined from the numerical simulations and related to the buoyancy speed. The impact force on the cylinder rises to a peak immediately after the arrival of the gravity-current head. We propose a set of new drag and lift coefficients using a gravity-driven pressure as a reference for the impact force of the non-Boussinesq current. The peak impact force, made dimensionless by the gravity-driven pressure, is found to be relatively independent of the density difference, regardless of how large the current density may be.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
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".