Drag on circular cylinders with porous outer layers in turbulent cross-flow
Bibliographic record
Abstract
Abstract The effects of free-stream turbulence intensity and porosity on the drag on cylinders with porous outer layers in cross-flow was investigated experimentally. This work is motivated by the need to better model spotting—a forest fire propagation mechanism in which burning branches and other debris (termed firebrands) are transported away from the main fire by the prevailing wind and ignite new fires. Multiple levels of background turbulence were studied by using no grid, passive grids, and an active grid to generate turbulence intensities of 0.4%, 1.7%, 2.7% and 12.4%. The porous char-layer on the outer surface of firebrands was mimicked by wrapping wire meshes (of 10, 20 and 40 pores per cylinder diameter or PPD) around the cylinders, each to three different layer-thickness fractions ( 1 / 16 , 1 / 8 and 1 / 4 ) of the cylinder’s outer diameter. The drag on one smooth cylinder and nine cylinders with porous outer layers was measured for Reynolds numbers in the range 7000–17 000, at the aforementioned four turbulence intensities. The results showed that (i) the free-stream turbulence intensity and PPD of the wire meshes affect the Reynolds number dependence of the drag coefficient; (ii) the drag coefficient increases with free-stream turbulence intensity when it is relatively low (0.4%–2.7%), then decreases at high intensities (12.4%), and this decrease is more pronounced as the PPD increases; (iii) the drag coefficient increases with the thickness of the porous layer, and asymptotes to an effectively constant value after a critical thickness of about 1 / 8 of the cylinder’s diameter; and iv) the drag coefficient exhibits a non-monotonic dependence on the PPD of the wire mesh. These results demonstrate the importance of accounting for free-stream turbulence intensity and the parameters that characterize the porous outer layers of cylinders when modeling the drag on firebrands, or in other applications in which there is cross flow over cylinders with porous outer surfaces.
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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".