Three dominant themes from the discussion
| Theme | Supporting quote |
|---|---|
| 1. Roughness can lower drag, overturning the “smooth‑is‑best” myth | “It’s long been accepted that the smoother the surface, the lower the aerodynamic drag. That turns out not always to be the case.” — mlmonkey |
| 2. This effect is different from golf‑ball dimples or shark‑skin riblets; it works by delaying laminar‑to‑turbulent transition rather than by turbulent‑flow shaping | “This principle is fundamentally different from the effect of dimples on golf balls. Dimples reduce pressure resistance by intentionally turbulizing the airflow and suppressing backward separation. DMR, on the other hand, delays the switch from laminar to turbulent flow by means of random and minute irregularities.” — staplung |
| 3. Practical adoption faces hurdles: retrofitting existing wings, maintaining a precise roughness, and certification concerns | “If it works as they state it does, it's a virtually free same‑day fuel efficiency boost.” — sgc “The surface would be subject to erosion from dust, ice, volcanic ash, and rain/water. The erosion is a problem that sees significant mitigation.” — leptons |
Summary
The thread revolves around three points: (1) the surprising discovery that carefully engineered micro‑roughness can reduce drag, contradicting the long‑held belief that smoother surfaces are always optimal; (2) this phenomenon is mechanistically distinct from familiar drag‑reduction tricks like golf‑ball dimples or shark‑skin riblets; and (3) while the potential fuel savings are enticing, real‑world issues of durability, maintenance, and regulatory approval could slow implementation.