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尾翼空气动力学abc之气流分离和失速(有很多专业词语我不知如何翻译为中文，只好根据自己理解翻出，故把原文贴出，请国内同行告知正确专业术语称呼）
Blown Rear wings: seperating and stalling
NOTE: Update on McLarens Snorkel\Rear wing here
浏览附件rearwing_cfd.jpg
Renaults CFD shows how the flow passes around a multiple element rear wings
F1赛车的尾翼产生了整车1/3的下压力。但是尾翼也有副作用，它赛车在高速行驶中会产生大量的阻力。想要提高最高时速，降低空气阻力是最重要的。很显然，对于尾翼来说，想要增加上述两个力中的一个力另一个力必然也会随之增加，反之亦然。所以在弯道的时候，我们需要高下压力、高阻力的组合保证强有力的抓地，在大直道的时候，我们会想尽可能的增加最高时速，这时下压力就不那么重要了，我们就会想尽可能的减少阻力。
For an F1 car the rear wing creates around a third of the cars downforce. But running at high speed the drag from the rear wing is tremendous. Anything that reduces the drag of the rear wing will aid top speed. If this can be done in a non linear way, that is; high downforce\drag at lower speeds increasing towards top speed and then less drag only at speeds where car is in a straight line and doesn’t need downforce, then laptimes will show an improvement.
浏览附件single_seperating1.jpg
A single element wing sees the flow separate (circle) at steep angles
当气流流过尾翼的下表面，后缘气流会倾向减慢速度并且分离（译者：下表面气流首先会加速，过峰值点后由于逆压，气流会减速，减到无力抵抗逆压的时候，气流就会向车头流，分离就会发生），大多数情况下，这是我们不愿看到的，因为后缘分离产生了很多的空阻。但是当超过临界点，尾翼气流完全分离从而导致失速的时候，空阻会大幅减小，下压力也会戏剧性的降低。
As airflows over the surface of a wing it has a tendency to slow down and separate from the wing. Particularly underneath the wing which runs at a lower pressure than the top surface. This separation initially reduces efficiency by adding drag to the wing, before the airflow totally breaks up and the wing stalls. When a wing stalls the wing loses most of its downforce and drag.
浏览附件single_stalled.jpg
A single element wing will then stall, as the flow breaks up under the wing
尾翼攻角（倾斜角）越大，气流分离的可能性就越大。为了改善这种状况，空气动力设计者把尾翼分成了独立的几片小翼，小翼中间留出了一点空隙，尾翼上表面的高压气流通过这些缝隙流到了下表面，这样就加速了翼下气流的速度。
The steeper a wings angle, the greater chance of separation. To combat this aerodynamicists need to speed up the flow near the wings surface, to do this they split the wing into separate elements, this creates a slot. Which sends high pressure air from above the wing through the slot, which then speeds the local flow underneath the wing. The more slots the steeper the wing can run.
浏览附件two_element1.jpg
With a two element wing, flow passes through the slot to prevent seperation
在90年代，规则对尾翼片的数量还没有限制。渐渐的，FIA觉得尾翼产生下压力有点高了，所以他们慢慢加强了对小尾翼片数量的限制，最初限制4个，后来改为3个直到现在的2个。现在各队的尾翼都是有2小片组成，一个主翼和一个副翼，主翼在前，副翼在后。这样的话尾翼理论上就只有一个间隙。但是这项规定对间隙的定义很含糊，所以如果你要在主翼中间开一个15cm的小缝，也不用遮遮掩掩，规则管不了你。所有车队在n年前就这么干了。
In the nineties teams were unlimited in the number of elements they could use. Slowly the rulemakers sought to reduce the wings potential for downforce and reduced the number of elements (defined as ‘closed sections’ within the rules), initially to four then three and currently two. Modern rear wings are made up to two elements, a main plane (the forward section of wing) and a flap (which sits behind it). Thus the wing is intended only to have a single slot and hence only one place to speed up the flow under the wing. However the rules are typically vague, thus a small 15cm section in the middle of the wing is exempt from this rule, teams have been adding a slot in this area for several years now. This slot is the same dimension on the front as it is on the back of the wing, so there has been no issues of legality within the rules, most team run a wing of this configuration.
去年BMW Sauber和McLaren的尾翼开的15cm的小缝有点不一样，这缝的入口向出口会慢慢变宽，再出口出甚至跟整个尾翼一样宽。根据设计，气流会以指定的角度流向尾翼下表面，差不多与通过尾翼的大部分气流平行。这有钻了一个规则的空子，虽然缝的尾部已经于尾翼一样宽，但是头部却符合’只能开在尾翼中间‘的规定，而且主翼依然完整，小翼个数仍是2个。这样’伪三翼‘的设计增加了尾翼的临界攻角，提供了更大下压力的可能性。今年Williams也是这样设计了他们的尾翼。
Last year BMW Sauber and McLaren ran wings with the narrow 15cm opening on the front of the wing, but this inlet diverged to make a slot the full width of the rear wing (normally within the main plane). This slot was aligned to send its airflow at an acute angle, roughly inline with the general flow over the wing. Again this was deemed legal as the slot made the wing profile an ‘open section’ only in the middle of the wing, where as the outers spans remained a ‘closed section’ albeit one with a “U” shape. With this design the slot could allow the entire wing to be steeper and not just the geometry in the middle 15cm of the wing. This year Williams have joined the group running these sorts of wings.
浏览附件blown_flap.jpg
With a blown wing, the extra inlet\outlet creates a legal second slot
之前各车队都在探索如何利用尾翼失速来减小阻力，增加赛车的最高时速。他们发现，通过可变尾翼，在高速状态下，尾翼上的缝隙变小，使尾翼失速。FIA通过加强强度测试和强制slot gap separators的手段阻止了这种设计。现在slot gap separators是尾翼的强制部件，它是一块在两片尾翼之间固定的一块板，这样一来这两片尾翼就不能移动了(求清晰大图）。
Again previously teams have sought to use the wing stalling to gain top speed (from the reduced drag). By flexing the wings at higher speed, the wings move to create smaller slot gaps and this leads to the wings stalling. The FIA has acted with both load tests and in the past few year slot gap separators to prevent this practice. Slot gap separators are now mandated for the rear wing, and appear a plate fitted around the profile of the two wing elements to prevent them moving.
McLaren 2010的尾翼并没有在主翼上开缝，而是开在了副翼上。大家都在投诉FIA说这样是犯规，如果这真的是不符合规定的话，McLaren就是在利用它使尾翼失速。（我看八成是）
The McLaren 2010 wing uses a slot in the flap (not the main plane), this time fed by the shark fin and an opening above the drivers head. If the teams’ protests about its legality are true, then the issue is that McLaren are using the slot to stall the wing.
浏览附件mclaren_stalled.jpg
A slot in the flap could break up the airflow and allow the wing to stall
我看有这么几种可能：
第一种可能是这样开缝会把气流导向不同于主要气流的方向，如果正好与主气流垂直，开缝出来的气流足可以把主气流干掉导致尾翼失速。
第二种可能是在低速状态下，开缝出来的气流可以帮助维持整体气流干净。在高速状态下，开缝会组织气流通过，这样的话开缝就不会使尾翼失速。
This could be possible in several ways; one could be having the slot orientated differently to the airflow over the wing, if it were at nearer right angles to the flow it could blow hard enough to disrupt the airflow enough to stall the wing. Another solution might be that the slot blows at lower speed maintaining a clean airflow over the wing, then at higher speed the slot chokes with the greater airflow trying to pass through it, the slot no longer blowing stalls the wing.
在上述设计的基础上，只要稍加修改调试，尾翼就会在低速状态下正常工作，提供下压力，在急速状态下使尾翼失速，降低阻力。目前的疑点就是，车手可控通气管的谣言是不是真的？到底会有多大功效呢？
These approaches would have to be tuned to have no effect at speeds lower than the top speed on the straight, thus the wing would provide normal downforce until near top speed. Then near top speed the flow through the slot would start disrupt the wings flow and stall the wing. The difficulty in getting this tuning to work is what’s given rise to the rumour about the driver operated snorkel duct on the McLaren.