科学与数学ciechanow.ski编辑精选
翼型
Airfoil
2024 — 2026，它一次次回到首页
黑点是上首页（≥ 50 分）的那次投稿，空心点是没冲上去的投稿，点越大分数越高。
导读
这是 ciechanow.ski 的又一篇交互式科普长文，用可拖动的动画讲解机翼（翼型）如何产生升力，涉及气流、压力与攻角等概念。作者此前关于船帆、螺旋桨等主题的同类文章曾多次广受好评。
为什么经久不衰：它把一个被无数错误解释（如'等时理论'）困扰的经典问题讲得直观又严谨，动画交互让抽象的空气动力学变得可感，多年后仍是学习升力原理的最佳入门材料之一。
HN 评论精选
经典 NACA 翼型至今仍是设计飞机的现成选择，说明其早已被优化到位
很有意思的是，许多飞机设计中使用的翼型是 NACA 在 1920-30 年代推导出来的。你会以为有了现代计算机软件能设计出更好的翼型，但这些形状似乎早已通过手工计算和实验在数学上被完善了。如今想设计飞机，只需根据所需速度、气压等参数从表格里查出合适的 NACA 翼型即可。
porphyra查看英文原文
It's pretty interesting that many airfoils used in aircraft design were derived by NACA in the 1920s and 1930s [1]. You'd think that with modern computer software it would be possible to design better airfoils, but apparently, those shapes have already been mathematically perfected by hand and by experiment. So nowadays if you want to design a plane you can just look up the desired NACA airfoil from a table based on the speed, air pressure, etc that you require. [1] https://en.wikipedia.org/wiki/NACA_airfoil
升力的关键在于机翼把大量空气向下偏转，翼型形状是被夸大的干扰因素
我希望所有讲飞机为什么能飞的文章都从一块平板翼型讲起。翼型形状完全是干扰项，妨碍人们理解真正发生的事。任何把手伸出行驶车窗外的人都知道，产生升力不需要花哨的形状。很多人误以为升力来自伯努利定律——机翼上表面路程更长所以气流更快——这几乎是胡说，因为飞机显然能倒着飞。飞机真正的原理是：向前飞行时把大量空气向下偏转，是'推开'空气获得升力。
onetimeuse92304查看英文原文
I wish every presentation on how planes fly started with an actual flat plane. A wing that has a flat crossection. I think the shape of the airfoil of the wing is absolutely distracting and prevents people from understanding what is really happening. Every person who ever stuck a flat object outside the window of a moving car knows that you do not need a fancy shape to have lift. And so many people are stuck thinking that the shape of the airfoil is responsible for the plane to be able to fly, supposedly because the air needs to run a longer way around the foil above the wing than below the wing. And this somehow causes pressure difference due to Bernoulli law and this is what keeps the plane up. Which is almost total BS because planes can obviously fly inverted. Now I admit I only skimmed the article, and although the animations are beautiful, I am missing what really is key to understanding of what is happening. I am looking for a bigger, far away view of the wing and showing what happens to the air BEHIND the wing. Because how the plane really works is as it flies forward, it diverts large masses of air downwards. It pushes off of air. Part of the air is diverted by the lower portion of the wing, but the much larger portion of lift is generated by larger masses of air above and behind the wing. Those can be thought as being sucked down behind the wing (if you look at it from the point of view of a stationary air mass, not from the point of view of the wing). And the main role of the airfoil is to keep that mass of air behind the wing stuck to the airfoil at wide range of angles and speeds as possible, because a flat sheet is very poor at doing this.
提出顺风与升力关系的疑问，引发对参考系问题的讨论
在这个细节层面上我一直没搞明白的是，顺风如何让飞机飞得更快。换句话说，如果气流从后面来，升力方程应该失效、飞机应该掉下来才对。（附链接讨论）
1970-01-01查看英文原文
Something that was never clear to me at this level of detail is how a tailwind enables an airplane to move faster. In other words, if the airflow is coming from behind, the lift equation should fall apart and the airplane should fall out of the sky. https://www.skytough.com/post/tailwinds-make-plane-faster
固定翼飞行原理其实很直观——机翼就是向下推空气的'线性风扇'
和往常一样，这看起来棒极了。让我困惑的是为什么有人觉得飞行难以理解。机翼就像一个把空气往下推的线性风扇，对我来说完全直观，难点只在于如何做得实用可控。相反，很多人对鸟类和昆虫的飞行毫不困惑，而那才是我觉得更难理解的。
globular-toast查看英文原文
This looks incredible as usual. What puzzles me, though, is why some people find flying puzzling. At least the kind that we do, ie. helicopters and fixed-wing aircraft. It's easy to accept a fan works: just put your hand there and feel the draft. A wing is just like a linear fan pushing air down. It's completely intuitive to understand for me. The difficulties are just in making it practical and controllable. Conversely, many people don't seem concerned at all with bird or insect flight, which I find a lot harder to understand.
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