A Fundamental Principle of Aeronautical Engineering Has Been Overturned

6 days ago

Researchers from Tohoku University's Institute of Fluid Science have discovered that adding a barely noticeable surface roughness (DMR, Distributed Micro-Roughness) with a roughness of only about 1.0% to a streamlined model can reduce aerodynamic drag by up to 43.6%, challenging the 80-year-old fluid dynamics belief that smoother surfaces always lead to less drag.
The breakthrough was achieved using the world's largest 1m Magnetic Suspension and Balance System (MSBS), which eliminates support interference in airflow measurements, allowing precise detection of drag changes. High-resolution simulations and oil-flow visualization further confirmed that the drag reduction is due to changes in the transition region from laminar to turbulent flow, not pressure drag.
The findings, published in the Journal of Fluid Mechanics on May 7, 2026, overturn a long-standing assumption and open new possibilities for next-generation energy-saving technologies, such as in aircraft and automobiles, by leveraging controlled surface roughness for enhanced aerodynamic efficiency.

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