Novel Time-Resolved Pressure Measurements on an Airfoil at a Low Reynolds Number
Bibliographic record
Abstract
2This work focuses on time-resolved surface pressure measurements on an airfoil operating in low Reynolds number flows. The experiments were performed on a NACA 0018 airfoil at a chord Reynolds number of 100,000. The results are presented for two angles of attack, eight and twelve degrees, representative of two flow regimes common to airfoil operation at low Reynolds numbers, separation bubble formation and separation without subsequent reattachment. An array of twenty-five microphones was embedded into the airfoil model to facilitate multi-point, time-resolved surface pressure measurements. A comparative analysis of mean pressure, velocity, and time-resolved pressure measurements is presented to determine what flow characteristics can be estimated using embedded pressure sensors. The results show that surface pressure fluctuations increase markedly past the separation location, reflecting the increase in the magnitude of velocity fluctuations in the separated shear layer undergoing laminar-to-turbulent transition. In the separation bubble, surface pressure fluctuations peak just upstream of reattachment, suggesting that time- resolved surface pressure measurements can be used to identify the presence and estimate the length of the separation region. The analysis of simultaneous velocity and pressure measurements shows that the characteristics of flow disturbances growing in the separated shear layer can be estimated from microphone measurements. In particular, the dominant frequency, convective speed, and growth rate of disturbances can be estimated without performing the extensive tests typically required when conventional velocity measurement techniques are used. However, when separation occurs without reattachment, the relatively large distance between the transitioning separated shear layer and the airfoil surface results in lower magnitude surface pressure fluctuations, which substantially increases the uncertainty of estimating flow characteristics based on microphone measurements for this flow regime.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| 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".