Flow leakage and Kelvin–Helmholtz instability of turbulent flow over porous media
Bibliographic record
Abstract
In the present paper, turbulent flow in a composite porous–fluid system, including a permeable surface-mounted bluff body immersed in a turbulent channel flow, is investigated using pore-scale large eddy simulation. The effect of Reynolds number (Re) on the flow leakage from porous to non-porous regions, Kelvin–Helmholtz (K–H) instabilities, as well as coherent structures over the porous–fluid interface are elaborated by comparing cases with three Reynolds numbers (Re = 3600, 7200, and 14 400). Results show that more than 52% of the fluid entering the porous blocks leaks from the first half of the porous region to the non-porous region through the porous–fluid interface. As the Re number increases from 3600 to 14 400, the flow leakage decreases by 24%. Flow visualization shows that the Re number affects the size of counter-rotating vortex pairs (CRVPs) and coherent hairpin structures above the porous block. At the Re = 3600, the CRVPs are larger and their centers locate farther away from the porous–fluid interface at Y/D ∼ 0.3 (D is two times of the distance between the centers of two consecutive pores), while at the highest Re number (Re = 14 400), they are 200% smaller and their centers become closer to the interface at Y/D ∼ 0.1. Moreover, turbulence statistics show that by reducing the Re number, turbulence production is delayed downstream; at the Re = 14 400, it begins from the leading edge of the porous block (X/D = 0), while at the Re = 3600, turbulence production is postponed and starts nearly at the middle of the porous block (X/D = 4.6). Also, quadrant-hole analysis indicates that increasing the Re number from 3600 to 14 400 strengthens sweep events and submerses the legs of coherent hairpin structures into the interface. Finally, the distribution of the pressure gradient for the three Re numbers confirms the occurrence of the K–H instability vortices over the porous–fluid interface. For Re = 3600, the K–H instability vortices show a linear growth rate in the vertical and horizontal directions with the slope of 0.136 and 0.05, respectively. However, by increasing the Re from 3600 to 14 400, the growth rate slope in the horizontal direction decreases by nearly 33.8%, while in the vertical direction, it increases by 200%.
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 distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 teacher head, 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".