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Dear Users,

I have a quick question. I have searched but could not find the exact answer. I have added the wind data to the case, which varies with time but constant in space. The values specified as U and V velocities in wind data. These values dictate the wind direction. The wind direction in wind data file is relative to North (0 degree) clockwise for North Hemisphere. So if it is 90 degree then it is blowing from the East.
How does Telemac read the wind direction: is it from East to West or from West to East for example when x=1 and y =0. Please clarify. Thank you in advance.

Kind Regards!

Violeta

Hi Violeta

A positive X component is a wind blowing towards East or coming from West. It is then a 270 degrees clockwise from North.


Mathieu

Thank you very much Mathieu for explanations.

Kind Regards!

Violeta

Hi,

Converting wind direction from UV can be confusing sometimes.

Could someone give me a brief instruction on how to convert the wind direction in TELEMAC from "clockwise from North"? what is the rule for it?

Thanks & Regards
Huy

Hi you can now use the keyword "SPEED AND DIRECTION OF WIND" to avoid playing with angles.

If I remember correctly, the direction using this keyword indicates the downwind direction of wind so you may have to add a 180 deg if you have the direction from which the wind is blowing (which is usually the case...)


Mathieu

Thanks Mathieu,

I often define the wind direction as "COMING FROM". So is this the case?

By the way, if I use the keyword: SPEED AND DIRECTION OF THE WIND, what do I prepare for the wind file? only wind speed? Or both speed and direction?

Regards
Huy

Hello Huy

The keyword SPEED AND DIRECTION OF WIND gives the speed and direction of wind. The direction is in degres (from 0 to 360), which means : angle 0 is given by y=0 and x=+infinity. The rotation positive direction is the trigonometric direction.

with my best regards

Riadh

Thanks Riadh for very clear answer!

Best Regards
Huy