Numerical investigation on transverse-gust-induced dynamic stall
Bibliographic record
Abstract
With the development of Urban Air Mobility (UAM), understanding atmospheric disturbances near the ground has become increasingly important. These disturbances significantly impact low-altitude, low-speed flight vehicles, particularly in urban or mountainous environments where gusts are frequent. Flows resembling transverse gusts can alter the effective angle of attack (AOA), potentially triggering dynamic stall. Dynamic stall is a fluid dynamics phenomenon that occurs when the AOA of an airfoil alters around a high value that causes the airfoil to enter and exit the stall regime, leading to unsteady flow phenomena such as delayed vortex shedding and hysteresis effects that differ significantly from those in steady conditions. The phenomenon had been extensively studied using pitching wings. In our recent research, the transverse-gust-induced dynamic stall was confirmed experimentally by employing a stationary NACA0012 wing encountering transverse gusts (maximum amplitude ~ 7 deg) at transitional Reynolds numbers (Re ~ 105, Mach ~ 0.03) at the low-speed wind tunnel of the Royal Military College of Canada (RMC).To model the gust-induced dynamic stall, two-dimensional (2D) Large Eddy Simulations (LES) were first performed using an in-house code of the National Research Council Canada based on the RMC experimental setup. The Smagorinsky sub-grid scale model was implemented in the code, and a hybrid upwind/centred scheme was used for discretization. The split-velocity method was employed to introduce gusts in incompressible viscous flows. These numerical results, validated against experimental data, successfully reproduced the flowfield associated with the gust-induced dynamic stall process and supported its similarity to pitch-induced dynamic stall. However, a key experimental observation, the secondary lift loop due to delayed vortex shedding, was not captured, which highlighted inherent limitations of 2D LES.To address this, a three-dimensional (3D) LES study is conducted. The results confirm the presence of the secondary lift loop and demonstrate a similar pattern for the moment coefficient, consistent with experimental findings. Delayed vortex shedding is observed after the effective angle of attack reaches its maximum value. The study provides a comprehensive analysis of the gust-induced dynamic stall process, encompassing flow separation, vortex evolution, and flow reattachment, which are comparable with the experimental observations of pitch-induced dynamic stall. Furthermore, the 3D LES underscores the critical role of spanwise flow effects and vortex structures, which are absent in 2D simulations. These numerical simulations offer valuable insights into the mechanisms of dynamic stall induced by transverse gusts, advancing our understanding of this complex aerodynamic phenomenon.
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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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".