Furthermore, the DMR-applied surface consistently showed a drag coefficient lower than that of the smooth surface up to the highest measured Reynolds number (3.6 x 10⁶)
This is the most surprising finding to me. The treated surfaces even exhibited lower drag in the turbulent flow regime.
Wait, is it also lower in the laminar region? Or is it higher in the laminar region, but laminar region lasts longer so overall improvement? Man a graph would be nice...
Thanks, I can't read the notes but the graph is pretty good.
Edit: ... Coefficient of drag seems same in laminar regime, the surface treatment seems to only improve efficiency or make no change
All it took was for aeronautical engineers to go out and play a single round of golf.
From the article:
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 transition [to turbulent boundary layer flow], thereby suppressing not pressure resistance but the wall friction itself. They are opposite mechanisms.
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