目前分類:Hobbies (14)
- Aug 26 Wed 2009 08:16
菜園記
- Aug 25 Tue 2009 11:57
玉米園
- Jul 22 Wed 2009 20:45
太陽咬一口 月亮說yummy
- Oct 24 Fri 2008 23:36
黑暗騎士 Joker小丑
- Oct 19 Sun 2008 20:06
生活的重心是....
- Oct 07 Tue 2008 11:57
我愛小美
- Feb 04 Mon 2008 21:53
會不會破一千
- Jan 09 Wed 2008 23:04
風剪-wind stress
好奇 可以殺死好多隻貓
奇怪 為什麼會有這種要殺貓的說法
剛剛看空中浩劫-哥倫比亞052班機 提到"風剪" 光是看中文就讓我很好奇了 我卻聽成...wind share?! 真的是耳朵有問題
於是
http://www.answers.com/topic/wind-stress?cat=technology
Wind stress
The drag or tangential force per unit area exerted on the surface of the Earth by the adjacent layer of moving air. Erosion of ground surfaces and the production of waves on water surfaces are manifestations of wind stress. Surface wind stress determines the exchange of momentum between the Earth and the atmosphere and exerts a strong influence on the typical variation of wind through the lowest kilometer of the atmosphere. Estimated values of the surface wind stress range up to several dynes per square centimeter (0.1 pascal), depending on the nature of the surface and the character of the adjacent airflow. See also Meteorology.
Significant stresses arise within the lower atmosphere because of the strong shear of the wind between the slowly moving air near the ground and the more rapidly moving air a kilometer above and because of the turbulent nature of the airflow in this region. The turbulent eddies referred to here have characteristic dimensions ranging up to a few hundreds of meters.
Wind pressure is the force exerted by the wind per unit area of solid surface exposed normal to the wind direction and is also known as dynamic pressure. In contrast to shearing stresses, the wind pressure arises from the difference in pressure between the windward and lee sides of the exposed surface. Wind pressure thus represents a substantial force when the wind speed is high. See also Wind.
The drag or tangential force of the wind on the sea is expressed in units of dynes per square centimeter or micronewtons per square meter but is normally taken to represent the mean drag over an undefined area, perhaps several kilometers square, containing many waves. It is usually related to an appropriate time and space average of the wind near the sea surface (at 10 m above the mean level, for example).
The drag coefficient over the sea is an important quantity in both meteorology and oceanography since it relates the wind speed to the drag, which generates ocean waves, drives the ocean currents, and sets the scale of the atmospheric turbulence that transfers water vapor and heat from the ocean to the atmosphere to provide the energy for clouds and weather systems. The drag coefficient of the sea surface depends on the wave field and on the turbulent structure of the flow in the air and the water. Present knowledge of the complicated fluid mechanics involved is not sufficient to allow theoretical calculation of it. See also Atmospheric general circulation; Maritime meteorology; Ocean circulation; Ocean waves.
There is substantial agreement that the drag of the wind on the sea is small relative to that of a fixed soil surface with the same geometry. It is largely independent of the fetch and so seems to depends less on the larger waves than on the short waves and ripples. Surface-active agents, which affect the shortest waves, may therefore be important.
另一個
http://oceanworld.tamu.edu/resources/ocng_textbook/chapter04/chapter04_05.htm
The wind, by itself, is usually not very interesting. Often we are much more interested in the force of the wind, or the work done by the wind. The horizontal force of the wind on the sea surface is called the wind stress. Put another way, it is the vertical transfer of horizontal momentum. Thus momentum is transferred from the atmosphere to the ocean by wind stress. Wind stress T is calculated from:
T = ñ CD U210
壓力還可以算出來耶…傑克這是太神奇的有趣呀!!!
- Jan 08 Tue 2008 13:32
騎鐵馬的利與弊
- Jan 07 Mon 2008 08:45
風信子全開
- Jan 04 Fri 2008 13:08
風信子 趴兔
- Dec 28 Fri 2007 13:00
小米
呵....這個主人很變態 根本就是在整他.... 雖然我也會這麼做
呵....這個也是.....舌頭到處舔...就是想吃
看到畫面 也回想起皮
不說了
又是個傷心往事
- Dec 27 Thu 2007 13:19
捻花惹草-風信子篇
- Dec 09 Sat 2006 21:07
Keroro