Experimental Investigation of Flow Over a Backward-Facing Step in Proximity to a Flexible Wall
Bibliographic record
Abstract
Turbulent flow between a flexible wall and a solid surface containing a backward-facing step (BFS) was investigated using digital particle image velocimetry (PIV) and high-speed photography. Motivation for this study stems from paper manufacturing industry, where high-speed, wall-bounded jets of air are employed in air clamp devices to precisely position moving sheets of paper at the specified locations with respect to other equipment. In the current investigation, stationary sheet of paper under tension was positioned in proximity to the BFS. The incoming air flow emerged from a planar nozzle that was located in the solid wall upstream of the BFS. Curvature of the nozzle wall resulted in a favorable pressure gradient condition. As a result, the flow upstream of the BFS was attached to the solid wall due to the Coanda effect. Flows corresponding to two values of the Reynolds number (3000 and 3600) based on the step height and the maximum flow velocity at the step location were characterized in terms of patterns of instantaneous and time-averaged velocity, out-of-plane vorticity, streamline topology, and turbulence statistics. In addition, paper sheet oscillation was characterized using high-speed photography. Frequencies of the natural vibration modes of the flexible wall (paper sheet) were well separated from the hydrodynamic frequencies corresponding to the oscillations of the shear layer downstream of the BFS, which resulted in the absence of resonance in the system and low characteristic amplitudes of the paper sheet oscillation. In the time-averaged sense, interaction between the separated flow downstream of the BFS and the flexible wall (paper sheet) resulted in deformation of the paper sheet and formation of diverging channel geometry between the sheet and the solid wall. As the inflow velocity increased, the paper sheet was pulled closer to the surface of the air clamp, which resulted in increased confinement of the incoming Coanda jet. The flow reattachment length calculated on the basis of time-averaged flow patterns increased with the increasing Reynolds number.
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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 | 0.001 | 0.001 |
| 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".