Hi, I would like to know, if you get the data for 24 hours of wind, how do you calculate it for weeks, months, half yearly & yearly? I would be very much enthusiastic to learn, if there is any way of video of learning that indicates "feasibility study of 1MW(assuming) wind turbine"
I would consider maybe a brief intro to the Monin-Obukhov Length (L), (defined as that height at which turbulence is generated more by buoyancy than by wind shear. In the daytime over land, L is typically between 1 to 50 meters.
Hi Mr, Thank you very much, Please how does the wind vary with time, and how to draw wind speed(m/s ) according to the time ??Thank you. quite cordially.
Dear Driss I now have an answer for you from Sven-Erik Gryning: "Thank you for the question, but I am not quite sure what exactly you are hinting at because it depends on the time scale. The daily variation of the wind speed over homogeneous terrain is explained in the Cousera course - near the ground low wind speed during the night as compared to daytime, and this effect is not present over the sea, you can find more information in Gryning et al (2016). This characteristic diurnal behavior disappears higher up in the atmosphere - say at about 100 - 200 m. A good way to illustrate the time wise behavior of the wind is by calculating the power spectra. A spectrum provides information on how the total variance of the wind fluctuations in time is distributed on the frequencies. It has a -5/3 power law behavior for high frequencies connected to dissipation of turbulence and the low frequencies gives information about the diurnal or even longer wavelength related to the weather systems. I do not know if this was helpful, if not please ask again." Best regards Betina Brink Laursen DTU Wind Energy Communications
Hi Mr, Sven-Erik Gryning Thank you for your response . Please I modeling wind turbine and control system ( Matlab - Simulink ) I want to gererate real wind speed profile ( from 3 to 20 (m/s) with time (s) vaie from 0(s) to 180(s) ()for example . Very best regards
Dear Niaz I apologize for the late reply which is due to the summer holiday season. I have contacted our researchers and will get back to you with an answer as soon as I hear back from them. Best regards Betina Winther DTU Wind Energy communications
Dear Niaz Here is the reply from Sven-Erik Gryning "For conditions where the logarithmic wind profile can be applied, the friction velocity (u-star) can be determined when the wind speed is known at one height, the surface roughness and a value is chosen for the von Karman constant (usually 0.4). The surface roughness is best estimated from look up tables. If the wind speed is available at two heights, the logarithmic wind profile can be formulated for each height and used to eliminate the surface roughness. The friction velocity can also be directly measured with a sonic anemometer." Best regards Betina Winther DTU Wind Energy communications
Hi,
I would like to know, if you get the data for 24 hours of wind, how do you calculate it for weeks, months, half yearly & yearly?
I would be very much enthusiastic to learn, if there is any way of video of learning that indicates "feasibility study of 1MW(assuming) wind turbine"
I would consider maybe a brief intro to the Monin-Obukhov Length (L), (defined as that height at which turbulence is generated more by buoyancy than by wind shear. In the daytime over land, L is typically between 1 to 50 meters.
So can you have strong gusts at the surface if the pressure gradient is weak above the boundary layer?
Hi Mr,
Thank you very much, Please how does the wind vary with time, and how to draw wind speed(m/s ) according to the time ??Thank you.
quite cordially.
Dear Driss
I have contacted Sven-Erik and will get you an answer ASAP.
Best regards
Betina Brink Laursen
DTU Wind Energy Communications
Dear Driss
I now have an answer for you from Sven-Erik Gryning:
"Thank you for the question, but I am not quite sure what exactly you are hinting at because it depends on the time scale.
The daily variation of the wind speed over homogeneous terrain is explained in the Cousera course - near the ground low wind speed during the night as compared to daytime, and this effect is not present over the sea, you can find more information in Gryning et al (2016). This characteristic diurnal behavior disappears higher up in the atmosphere - say at about 100 - 200 m.
A good way to illustrate the time wise behavior of the wind is by calculating the power spectra. A spectrum provides information on how the total variance of the wind fluctuations in time is distributed on the frequencies. It has a -5/3 power law behavior for high frequencies connected to dissipation of turbulence and the low frequencies gives information about the diurnal or even longer wavelength related to the weather systems.
I do not know if this was helpful, if not please ask again."
Best regards
Betina Brink Laursen
DTU Wind Energy Communications
Hi Mr, Sven-Erik Gryning
Thank you for your response . Please I modeling wind turbine and control system ( Matlab - Simulink ) I want to gererate real wind speed profile ( from 3 to 20 (m/s) with time (s) vaie from 0(s) to 180(s) ()for example .
Very best regards
sir how to find u* from given wind speed?
Dear Niaz
I apologize for the late reply which is due to the summer holiday season. I have contacted our researchers and will get back to you with an answer as soon as I hear back from them.
Best regards
Betina Winther
DTU Wind Energy communications
Dear Niaz
Here is the reply from Sven-Erik Gryning
"For conditions where the logarithmic wind profile can be applied, the friction velocity (u-star) can be determined when the wind speed is known at one height, the surface roughness and a value is chosen for the von Karman constant (usually 0.4). The surface roughness is best estimated from look up tables. If the wind speed is available at two heights, the logarithmic wind profile can be formulated for each height and used to eliminate the surface roughness.
The friction velocity can also be directly measured with a sonic anemometer."
Best regards
Betina Winther
DTU Wind Energy communications
whaou this video is so sick OMG