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[[Image:DiagramApparentWind.gif|thumb|325px|V = boat speed, H = head wind, W = true wind, A = apparent wind, α = pointing angle, β = angle of apparent wind]]
 
'''Apparent wind''' is the wind experienced by a moving object.
 
==Definition of apparent wind==
The ''Apparent wind'' is the wind experienced by an observer in motion and is the [[relative velocity]] of the wind in relation to the observer.
 
''Apparent wind'' [[velocity]] is the [[vector sum]] of the ''true wind'' and the headwind an object would experience in still air.  The headwind velocity in still air is [[Additive inverse|inverse]] of the object's velocity, therefore the apparent wind can also be defined as a vector subtraction: the '''''Velocity of the wind''' minus the '''Velocity of the object'''''.
 
==A simple example==
Suppose you are riding a bicycle on a day when there is no wind. Although the wind speed is zero (people sitting still feel no breeze), you will feel a breeze on the bicycle due to the fact that you are moving through the air. This is the apparent wind.  On the windless day, the apparent wind will always be directly in front and equal in speed to the speed of the bicycle.
 
Now suppose there is a 5&nbsp;mph wind coming directly from the north. If you pedal at 10&nbsp;mph due north, you will feel an apparent wind of 15&nbsp;mph from the north.  But if you pedal 10&nbsp;mph due south, you will feel an apparent wind of 5&nbsp;mph from the south. The apparent wind is not only different in speed than the true wind (except when you are standing still), but may also be different in direction.
 
In these simple examples, the motion is parallel to the true wind which makes it easy to calculate the speed and direction of the apparent wind in relation to true wind speed (relative to the earth). When the motion is not parallel to the wind, one must use trigonometry to calculate the apparent wind.  Vector mathematics might also be useful in some cases.
 
==Apparent wind in sailing==
In [[sailing]], the apparent wind is the actual flow of air acting upon a [[sail]]. It is the wind as it appears to the sailor on a moving vessel.  
It differs in speed and direction from the '''true wind''' that is experienced by a stationary observer.
In [[nautical terminology]], these properties of the ''apparent wind'' are normally expressed in [[Knot (unit)|knots]] and [[degree (angle)|degree]]s.
 
==Calculating velocity and angle==
 
<math>A = \sqrt{W^2 + V^2 +2WV\cos{\alpha}}</math>
 
Where:
* <math>V</math> = velocity (boat speed over ground, always > 0)
* <math>W</math> = true wind velocity (always > 0)
* <math>\alpha</math> = true pointing angle in degrees (0 = upwind, 180 = downwind)
* <math>A</math> = apparent wind velocity  (always > 0)
The above formula is derived from the [[Law of cosines]] and using <math>\cos(\alpha') = \cos(180 \text{º}-\alpha) = -\cos(\alpha)</math>.
 
The angle of apparent wind (<math>\beta</math>) can be calculated from the measured velocity of the boat and wind using the inverse cosine in degrees (<math>\arccos</math>)
 
<math> \beta = \arccos \left( \frac{W\cos \alpha+V}{A} \right) = \arccos \left( \frac{W\cos \alpha+V}{\sqrt{W^2 + V^2 +2WV\cos{\alpha}}} \right)</math>
 
If the velocity of the boat and the velocity and the angle of the apparent wind are known, for instance from a [[Apparent wind#Instruments|measurement]], the true wind velocity and direction can be calculated with:
 
<math>W = \sqrt{A^2 + V^2 - 2AV\cos{\beta}}</math>
 
and
 
<math> \alpha = \arccos \left( \frac{A\cos \beta-V}{W} \right) = \arccos \left( \frac{A\cos \beta-V}{\sqrt{A^2 + V^2 -2AV\cos{\beta}}} \right)</math>
 
==Instruments==
The '''apparent wind''' on-board is often quoted as a speed measured by a [[Mast (sailing)|masthead]] [[transducer]] containing an [[anemometer]] and [[Weather vane|wind vane]] that measures wind speed in [[Knot (unit)|knots]] and wind direction in degrees relative to the [[Course (navigation)|heading]] of the boat. Modern instrumentation can calculate the true wind velocity when the apparent wind and boat velocity are input.
 
==Implications on sailing speeds==
In [[sailboat racing]], and especially in [[speed sailing]], apparent wind is a vital factor, when determining the [[points of sail]] a sail-boat can effectively travel in.
A vessel traveling at increasing speed relative to the ''prevailing wind'' will encounter the wind driving the sail at a decreasing angle and increasing velocity. Eventually, the increased drag and diminished degree of efficiency of a sail at extremely low [[Angle of attack|angles]] will cause a loss of accelerating force. This constitutes the main limitation to the speed of wind-driven vessels and vehicles.
 
[[windsurfing|Windsurfers]] and certain types of boats are able to sail faster than the true wind. These include fast [[multihull]]s and some [[Planing (sailing)|planing]] monohulls.  [[ice yachting|Ice-sailors]] and [[land sailing|land-sailors]] also usually fall into this category, because of their relatively low amount of [[drag (physics)|drag]] or [[friction]].
 
In the foiling AC72 America's cup catamarans,the boats sail through the water at up to double the environmental wind strength. The effect of this is to radically change the apparent wind direction when sailing "downwind". In these boats the forward speed is so great that the apparent wind is always forward-at an angle that varies between 2 and 4 degrees to the wing sail. This means that AC72's  are effectively tacking downwind, although at a greater angle than the normal 45 degree upwind angle,usually between 50 and 70 degrees.<ref>TVNZ Live America's cup Broadcast.Interview with Tom Schnackenburg. 22/9/2013</ref>
 
==Other areas of relevance==
In [[fixed-wing aircraft]], apparent wind is what is experienced on-board and it determines the necessary speeds for take-off and landing. [[Aircraft carrier]]s generally steam directly upwind at maximum speed, in order to increase apparent wind and reduce the necessary take-off velocity. Land-based [[airport]] traffic, as well as most mid-sized and large birds generally take off and land facing upwind for the same reason.
 
==Online calculation and graphical impact presentation ==
[http://web.me.com/cscholiers/Wind_%26_Apparent_Wind/True_and_Apparent_Wind.html Short introduction related to Kitebuggy, Kite-MTB, Kitesurf]<br />
[http://www.starpath.com/freeware/true_wind.htm Input Wind speed & Course in degrees and Course speed, as an input to calculate apparent wind speed and apparent wind angle]
 
==References==
{{reflist}}
 
== External links ==
* [http://sites.google.com/site/navigationalalgorithms/ Navigational Algorithms] Apparent wind soft, math: vector solution, and examples.
 
{{DEFAULTSORT:Apparent Wind}}
[[Category:Sailing]]
[[Category:Navigation]]

Latest revision as of 13:08, 12 November 2014

Alcohol can undoubtedly minimize your fertility levels and it may possibly also influence sperm depend in gentlemen. Check out what medicines you and your partner are taking even the ones that you think may not be affecting you could have bad side effects. Since most women do not get enough nutrients from their daily diet, start taking vitamin supplements when trying to conceive, which includes the B vitamins, folic acid and zinc. It also helps in alkalizing the body, creating a favourable environment for the sperm and fertilized egg. There are plenty of unknown hints and tips that can make playing of the game The Sims 2 a lot more fun.

Especially, do not take any medications without the advice from your family doctors. Sims are able to have sex with members of the opposite sex as well as members of the same sex. Even though it sounds crazy, the best option would be to give teens some form of birth control and actually allow them to have sex in their house. Woman ovulate about the 14th day so having intercourse during that time is crucial if you want to conceive. - You should try to stay away an evil magic spell to get pregnant that can lower your chances of getting pregnant, such as, alcohol, cigarettes, and any forms of caffeine.

Lisa Olsen's E book provides inspiration and some ideas to aid accomplishing pregnancy naturally. Conceiving a child maybe easy and simple of all things, yet, some married couples do find it hard to conceive for many reasons, this includes weak or low sperm count. Acupuncture balances the stage of hormones in your body which is incredibly critical for a woman to turn into a mother. The very best way is to use an ovulation kit which will tell you the most effective time to conceive and attempt for a newborn. When it is determined that you are ovulating it is recommended that you have sexual intercourse in positions that will help keep the sperm inside the body longer as this is a good way how to get pregnant quickly.

Just think about it for a moment, babies have an amazing effect on even the most hard-core men & women, a baby causes a staunch person go to all “gagga”. Crytorchilism also known as undesenced testicles, It uses to happen to premature child. I guess you get used to what you are given but I don’t think I would want to trade with another species. But this time can differ based on lots of factors: anxiety degree, illness, transforming your natural environment and the like. They do not discriminate based on your religion, and do not pass judgment on your circumstance.

The good news is that by reducing your exposure you'll actually get pregnant faster and easier. As a matter of fact, the Office on Women's Health states that for most patients, clomiphene is usually tried first. When you are bearing in mind how you can best get pregnant rapidly, try to bear in mind that pregnancy is awfully tough to control or force. “I was 43 when my first child was born and 45 when my third was born. Unlike conventional methods, the answer to the question of how to get pregnant can be painstakingly obtained through correct guidance and holistic therapeutic solutions.

When you loved this article and you would love to receive more information about how to get pregnant fast and easy (www.quebec-1759.info) generously visit our own website.

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