长达80多年的航空工程常识「表面越光滑，空气阻力越小」被推翻。东北大学流体科学研究所的Aiko Yakino团队利用分布式微粗糙度（DMR）证明，在无法以肉眼辨识的细微随机粗糙表面上，阻力最高可降低43.6%。研究在1米磁悬浮支撑系统（1m-MSBS）中进行，可在无接触状态下悬浮约1.07公尺的模型，并在雷诺数0.35×10^6至3.6×10^6范围内精密量测。

实验显示，DMR涂层将湍流转捩的临界雷诺数由约1.9×10^6提高到2.2×10^6，且在转捩区阻力最多下降43.6%，在最高测得雷诺数3.6×10^6时仍低于光滑表面。DMR采用两种形态：直径38至53微米的玻璃珠凸起，以及喷砂形成的凹陷；其高度仅为边界层厚度的1%。与鲨鱼皮式沟槽不同，DMR不依赖沿流向的精准加工，而是借由随机微小不规则延后由层流转为湍流。

为厘清机制，团队以高达45.38 million个壁面网格的LES与流场可视化分析发现，压力阻力的保守上限约为Cp≈0.00021，与理论值误差在1%内，但观测到的阻力下降约ΔCD≈0.001，约为该上限的5倍；即使完全消除尾部离流，也只能解释约20%的降幅。因此，DMR的主要效果不是抑制分离，而是直接降低壁面摩擦阻力。若应用于飞机，这种无需电力、无活动部件且各向同性的被动技术有望提升燃油效率、降低营运成本与二氧化碳排放。

For more than 80 years, aeronautical engineering assumed that smoother surfaces always mean lower drag, but a Tohoku University team led by Aiko Yakino showed that this is not universally true. Using distributed micro-roughness (DMR), the researchers reported up to a 43.6% reduction in aerodynamic drag. The measurements were made in a 1-meter magnetic support balance system (1m-MSBS), which levitated a model about 1.07 m long without support bars, over Reynolds numbers from 0.35×10^6 to 3.6×10^6.

The data showed that DMR raised the critical Reynolds number for transition from about 1.9×10^6 to 2.2×10^6, and the DMR surface stayed below the smooth surface’s drag coefficient even at the highest tested Reynolds number of 3.6×10^6. Two DMR forms were tested: glass beads 38–53 μm in diameter and a sandblasted concave pattern; the coating height was only 1% of the boundary-layer thickness. Unlike shark-skin riblets, which rely on grooves about 0.1 mm wide aligned with the flow, DMR uses random minute irregularities to delay the laminar-to-turbulent switch.

A large-eddy simulation with up to 45.38 million wall cells, combined with flow visualization, indicated that the main mechanism is not separation suppression but reduced wall-friction drag itself. The conservative pressure-drag upper limit was Cp≈0.00021, within 1% of theory, while the observed drag reduction was ΔCD≈0.001, about five times larger; even eliminating rear separation entirely would explain only about 20% of the reduction. Because DMR is passive, direction-independent, and needs neither moving parts nor electricity, it could lower fuel use, operating costs, and CO2 emissions in aircraft applications.