Analysis of Steady and Unsteady Flows Past Airfoils in the Proximity of the Ground at Low Reynolds Numbers
Bibliographic record
Abstract
This paper presents the analysis of the steady and unsteady flows past fixed and oscillating airfoils at low Reynolds numbers in the proximity of the ground. Various flight evolutions of the micro-air-vehicles take place in the proximity of the ground or a ceiling, which require the aerodynamic solutions in these conditions at the low Reynolds numbers. The unsteady flow problem is solved in a rectangular computational domain, obtained from the physical domain by time-dependent coordinate transformations for various subdomains, in which the boundary conditions are efficiently and rigorously implemented. Solutions for the aerodynamic coefficients of airfoils executing pitching oscillations in the proximity of the ground at low Reynolds numbers are obtained with an efficient numerical method developed by the authors for the time-accurate solution of the Navier-Stokes equations, which is second-order accurate in time and space. This method uses a pseudotime relaxation procedure based on artificial compressibility and a factored Alternate Direction Implicit (ADI) scheme for integration in pseudo-time. A second-order central finite difference formulation is used on a stretched staggered grid (which avoids the oddand-even points decoupling). A special decoupling procedure based on the continuity equation reduces the problem to the solution of scalar tridiagonal systems of equations, which enhances substantially the computational efficiency of the method. The influence of various flow parameters (Reynolds number, airfoil relative thickness and the amplitude and frequency of oscillations) on the aerodynamic coefficients (lift, drag, pitching moment and lift-to-drag ratio) and the flow separation in the proximity of the ground is also studied.
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 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".