Effect of Entrance Cross-Section on Bulk Swirl and Performance of an S-Duct Inlet in High Subsonic Flow
Bibliographic record
Abstract
Abstract For fuselage embedded engines, S-shaped ducts with multiple bends are usually employed to induct oncoming air. The combination of bends and diffusion creates a flow that routinely separates in regions of high-pressure gradient causing a concomitant reduction in static pressure recovery, a drop in total pressure, flow distortion and swirl at the engine face: the aerodynamic interface plane. This affects engine performance, stability margin, and safety of the integrated aircraft-engine system. It has previously been established that for a symmetric S-duct with a rectangular entrance, exit flow showed the presence of counter-clockwise, 10° bulk swirl. It was attributed to the axial transition of cross-section from a rectangular entrance to a circular exit and/or to high entrance Mach number. The present tests are done to investigate the exit flow bulk swirl and S-duct performance at Ma = 0.80 using a circular entrance. In addition, a 0.48 offset-to-length ratio, rectangular-entrance S-duct was tested at Ma = 0.80, 0.60 & 0.40. The S-duct was rapid prototyped in plastic using 3D printing. Stream-wise static surface and exit total pressure were measured using static taps and a 5-hole probe, respectively. The measured parameters were used to determine static pressure recovery, total pressure loss, exit flow swirl and pressure field polar distortion. These experiments provided information on flow mechanism and the evidence of the origin of bulk swirl in a symmetric S-duct with rectangular entrance.
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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 | 0.000 | 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) | 0.002 | 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".