Stability of Boundary Layers over Porous Walls with Suction
Bibliographic record
Abstract
Although there is considerable interest in using wall suction to increase boundary-layer stability, stability analyses suggest that porous walls are inherently destabilizing. We explore this contradiction by performing a spatial linear stability analysis of the asymptotic suction boundary layer using a realistic model of wall suction. The porous wall is modelled as a layer of rigid, homogeneous, isotropic, porous material of small permeability, in which inertial effects may be neglected. The porous layer is bounded above by a semi-infinite region in which a boundary layer is driven by a constant freestream velocity. The wall suction is created by applying a suction pressure to a semi-infinite region below the porous layer. Our stability analysis takes account of the full coupling between the flowfields in the boundary-layer and suction regions, governed by the Navier–Stokes equations, and the flow in the porous layer, governed by the volume-averaged Navier–Stokes equations. We find that small amounts of wall permeability destabilize the Tollmien–Schlichting wave and cause a substantial broadening of the unstable region. As a result, the stabilization of boundary layers by wall suction is substantially less effective and more expensive than what is predicted by classical boundary-layer theory.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| 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".