Characteristics of flow past elongated bluff bodies with underbody gaps due to varying inflow turbulence
Bibliographic record
Abstract
An experimental study was performed on two elongated bluff bodies with underbody gaps, a square-back Ahmed body and a cuboid, to investigate the effects of geometry and the approach flow conditions on the time-averaged and temporal characteristics. The flow fields produced from two approach turbulent boundary layers with moderate (∼4%) and high (∼7%) turbulence levels were studied using time-resolved and double-frame particle image velocimetry systems. With the moderate turbulence, the wake topology and the loci of the centroid of vortices exhibit the well-known toroidal structure behind the Ahmed body, though it is skewed away from the wall. Also, the regions of elevated Reynolds stresses are considerably larger in the upper shear layer compared to the lower shear layer due to the reduced underbody velocity. The dominant frequencies obtained from the velocity fluctuations, reverse flow area, and the coefficient of the first proper orthogonal decomposition (POD) mode are identical. The flow structures are more complex behind the cuboid and the Ahmed body mounted in the high turbulent flow due to the enhanced interaction between the lower and upper shear layers, which is also evident from the shape of the turbulent structures in these shear layers. Consequently, the dominant vortex shedding frequencies varied as the streamwise distance from the bodies increased. The probability density function of the reverse flow area and the POD analysis performed in the spanwise plane revealed that the bi-stability phenomenon is absent in the present study due to the significant modification of the wake topology.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".