Experimental investigation of the flow features around an elliptical Ahmed body
Bibliographic record
Abstract
The standard Ahmed body (SAB) with a rectangular rear end is a simplified, canonical bluff body geometry that shares similarities with generic road vehicles. It is known to produce flow separations and strong vortices at the rear end. The aerodynamic performance of vehicles is significantly affected by such three-dimensional flow structures. This work proposed a modified Ahmed body with an elliptical rear end called the elliptical Ahmed body. The study examines in detail the near-field characteristics of the flow over the elliptical Ahmed body at a slant angle of 25° with a low Reynolds number of 4.31×104 based on the model height. The principal flow features are analyzed using time-resolved and standard particle image velocimetry. The time-averaged and time-resolved analyses revealed a fully detached flow at the rear end that eliminated the slant separation bubble. Furthermore, a significant wake flow restructuring is found to curb the lower recirculation bubble and shift the upper recirculation bubble toward the slant surface. Thus, the elliptical curvature shifts the critical slant angle of 30° in SAB to 25°, which indicates transformation of the high-drag flow structures into low-drag. Several distinct Strouhal numbers are found over the slant surface (St = 0.55–0.88), which are higher than that of the SAB, while no significant change is found in the wake region (St = 0.23–0.50). In addition, the effect on coherent structures is evaluated using proper orthogonal decomposition and dynamic mode decomposition, which shows a considerable difference between the standard and elliptical Ahmed body wake structures. The results of this investigation show that body modification of the Ahmed body using elliptical curvature at the rear end can significantly affect the overall flow features and help improve the aerodynamic performance of the vehicles.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.001 | 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".