Unsteady Effects on Airfoils in the Ground Proximity due to Unsteady Flow Separations at Low Reynolds Numbers
Bibliographic record
Abstract
In a previous paper, the authors found that the aerodynamic coefficients of lift and drag displayed periodic variations in time due to the unsteady flow separations occurring at low Reynolds numbers on stationary airfoils at relatively small angles of attack. This paper presents the analysis of the unsteady flows past airfoils in the proximity of the ground, aiming to determine the influence of distance to the ground on these unsteady effects which are generated by the unsteady flow separations on the airfoils at low Reynolds number. It was found that these unsteady effects appear at lower angles of attack on the airfoils in the proximity of the ground than in free flight. Solutions are presented for the unsteady lift and drag coefficients of several NACA airfoils in the proximity of the ground, which incorporate the effect of the unsteady flow separations. These unsteady solutions are obtained with an efficient time-accurate numerical method developed by the authors for the solution of the Navier-Stokes equations at low Reynolds numbers, which is second-order-accurate in time and space. The paper presents a study of the influence of various geometric and flow parameters, such as the distance to the ground, the airfoil relative thickness and camber and the Reynolds number on the unsteady aerodynamic coefficients. The flow separation is also studied with the aid of flow visualizations illustrating the changes in the flow pattern at various moments in time for various distances to the ground.
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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 | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".