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| Remarkably valuable material is available these days on wikipedia.
|
| But I've got problems with this
|
http://en.wikipedia.org/wiki/Microburst
| text.
|
| Sailplaners will have a good understanding of natural air flow.
| This text seems to suggest that you can take an unenclosed 'parcel'
| of air, and move it through the surounding air, like you can throw
| a solid object through the air.
|
| I can't find good explanations of why the text is 'wrong'.
|
| Microburst
|
| From Wikipedia, the free encyclopedia
|
| [5]A photograph of the surface curl soon after an intense
microburst
| impacted the surface
|
| A falling potatoe may 'impact' the floor, but air can't impact the floor
| any more than a 'swirl' [being a separate volume of the liquid] inside
| your coffee cup can impact the surface.
|
| A microburst is a very localized column of sinking air, producing
| damaging divergent and [7]straight-line winds at the surface that are
| similar to but distinguishable from [8]tornadoes which generally have
| convergent damage.
|
| The 'localisation' is the problem.
| To move a small volume with respect to its surroundings, you have to
| apply energy to this 'localisated package' and not to its surroundings.
| I guess lightning/thunder does that ?
| Perhaps a laser could too.
|
| The term was defined by severe weather expert [9]Tetsuya Theodore
| Fujita as affecting an area 4 km (2.5 mi) in diameter or less,
| distinguishing them as a type of [10]downbursts and apart from common
| [11]wind shear which can encompass greater areas. Dr. Fujita
also
| coined the term macroburst for downbursts larger than 4 km (2.5 mi).
|
| A distinction can be made between a wet microburst which consists of
| precipitaiton and a dry microburst which consists of [12]virga. They
| generally are formed by precipitation-cooled air rushing to the
| surface, but they perhaps also could be powered from the high speed
| windsofthe [13]jet stream deflected to the surface in a
| [14]thunderstorm (see [15]downburst).
|
| Microbursts are recognized as capable of generating wind speeds higher
| than 75 m/s (168 mph; 270 km/h).
|
| Danger to aircraft
|
| See also: [17]downbursts
|
| The scale and suddenness of a microburst makes it a great danger to
| aircraft, particularly those at low altitude which are taking off and
| landing.The following are some fatal crashes that have been
| attributed to microbursts in the vicinity of airports:
| * [18]Delta Air Lines Flight 191
| * [19]Eastern Air Lines Flight 66
| * [20]Pan Am Flight 759
| * [21]USAir Flight 1016
|
| A microburst often causes aircraft to crash when they are attempting
| to land. The microburst is an extremely powerful gust of air that,
| once hitting the ground, spreads in all directions. As the aircraft is
| coming in to land, the pilots try to slow the plane to an appropriate
| speed. When the microburst hits, the pilots will see a large spike in
| their airspeed, caused by the force of the headwind created by the
| microburst. A pilot inexperienced in microbusts would try to decrease
| the speed. The plane would then travel through the microburst, and fly
| into the tailwind, causing a sudden decrease in the amount of air
| flowing across the wings. The sudden loss of air moving across the
| wings causes the aircraft to literally drop out of the air. The best
| way to deal with a microburst in an aircraft would be to increase
| speed as soon as the spike in airspeed is noticed. This will allow the
| aircraft to remain in the air when traveling through the tailwind
| portion of the microburst.
|
| OTOH I've heard the big-jet's 'exhaust' and downwash also
| 'stays together like a solid' and doesn't disperse.
|
| How much of this is true ?
|
| If you've got a conical bucket of white-water, with a mechanism
| to close off the lower 25% of the cone, can you project a black-ball
| of water down through the white-water, and capture it by closing
| of the lower clone section ?
|
| Or will the black-ball of water just be dispersed ?
|
| If an aircraft/bomber had it's front blown-off so that the
| pilots had no shielding in front of them, would they necessarily have
| near flying speed winds 'impacting' them, if the airflow had no
| 'reason' to flow in, 'cos it's got no low resistance path to flow out ?
|
| == Chris Glur.
|
Wackypedia can be edited by anyone, so you'll inevitably get
nut case rants along with solid information. Jimbo Wales doesn't care
as long as he profits by it.
Androcles.