Effects of freestream turbulence intensity on flow dynamics and vortical structures around a high-drag Ahmed body
Bibliographic record
Abstract
This study investigates the effects of freestream turbulence (FST) on the spatiotemporal flow dynamics around an Ahmed body with a slanted angle of β = 25° using time-resolved particle image velocimetry. Three FST intensities (Tu = 5.0%, 10.0%, and 15.0%) were generated using regular and fractal grids, and the results were compared with those obtained at a baseline turbulence level of Tu = 1.5% achieved in the absence of the grids. The size of the roof recirculation bubble decreased monotonically with increasing FST; however, the wake bubble size is independent of FST. Over the slanted surface, the bubble size increased with FST for Tu ≤ 10.0% and remained constant at Tu = 15.0%. The increase in the bubble size was attributed to a stronger spatial and temporal correlation between the C-pillar vortex and the separated shear layer from the slanted surface. FST also promotes turbulence transition by generating elongated streaks characterized by higher streamwise than wall-normal velocity fluctuations. The results also show that FST suppresses the magnitudes of Reynolds stresses over the roof and in the wake region and has no significant effects on the turbulence levels over the slanted surface. The spatiotemporal features were analyzed using velocity spectra and two-point spatial and space–time correlation coefficients, while spectral proper orthogonal decomposition was used to study vortical structures linked to dynamically important frequencies. FST suppressed the dynamically important frequencies of the vortical structure, including roof bubble pulsation, disrupted the flapping motion of recirculation bubbles in the wake, and reduced their spectral coherence.
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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 | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".