尾流形成的原理
张献忠简介
What is Wake Turbulence?
This is one topic which can be easily learned and understood but can be quickly forgotten as well. All aircraft in flight generate wake turbulence. The interesting fact is that, the heavier the aircraft the more vere the turbulence.
Defined by ICAO (Doc 9426) the term wake turbulence is ud to describe the “effect of two rotating air mass generated behind the wing tips of large jet aircraft”. The terms ‘wake vortex’ and ‘wake vortices” are other terms of ‘wake turbulence’, which describes the nature of the air战胜恐惧>肠胃宁
mass. Such wake vortices are two counter-rotating cylindrical air mass trailing from the aircraft which are generated the moment the aircraft lifts from the ground and ends when it touches down. A vortex circulation is outward, upward and around the wing tips when viewed from either ahead of or behind the aircraft.
工作表现评语
Generation and Movement of Vortex
隐没的反义词
Wake Vortex is a by product of lift and is prent behind every aircraft in flight. Lift is generated by the creation of a pressure differential over the aircraft wing surfaces.
The pressure differential over the wing (where low pressure occurs) and under the wing (where high pressure occurs) triggers the rollup of the airflow aft of the wing, resulting in rotating air mass trailing down stream of the wing tips.
Once the aircraft is airborne, two counter rotating cylindrical vortices like tho shown in figure 1 are created, which are hazardous to the following aircraft, especially during take off, initial climb, final approach and landing.Clo to ground, the wake vortices tend to drift down and move sideways from the track of the generating aircraft but may rebound upwards as well. Even though rearch conducted by FAA (Federal Aviation Administration) showed most of the energy is with in a few feet of the centre of each vortex, “pilots are advid to avoid a region within about 100 feet of the vortex core”.(Advisory Circular, AC NO:90-23 E, FAA. 01 Oct 1991)
尾流是指飞行中由于与空气的相互作用力，使经过的区域留有气流的扰动。它应该包括深夜伤感的句子2个部分：发动机喷流和翼尖涡流。在空中发动机喷流作用比较小，而翼尖涡流停留时间比较长，作用力大，所以一般认为尾流就是翼尖涡流。所谓的翼尖涡流是在飞行的航空器之后空气中两对以翼尖为中心、相对旋转的涡流。
产生原因：机翼的升力来自上下表面的压力差，下表面的压强大与上表面，而空气总是从高压区流向低压区。但机翼不可能无限大，所以总是有一部分空气绕过翼尖，从下表面流向上表面，因而以左右翼尖为中心各自形成一对涡流。从飞机后面看，左漩涡是顺时针方向，而右漩涡是逆时针方向。
翼尖涡流与升力是并存的，有升力就有翼尖涡流，没有升力就没有翼尖涡流。因此，落地的飞机在接地前有翼尖涡流产生，而接地后就没有。同样，起飞飞机在离地前是不产生翼尖涡流的，而一离地就会开始产生翼尖涡流。
P.S.关于直升机的尾流：同重量的直升机比固定翼飞机产生的尾流强，其原因就是悬翼的总面积远小于固定翼机，同样升力时上下表面的压力差要大得多，所以尾流要强很多。
