The blades of a wind turbine are ready to be installed on a turbine on top of a ridge. The horizontal blades are supported at each end by saw horses, when a storm front arrives. The turbine crew huddles in their truck as the rain starts and the wind picks up, increasing eventually to 25 m/s. Realizing that the wind coming up the western slope of the ridge roughly follows the 10° slope, the field engineer performs a quick calculation and drives his truck upwind of the blades to disrupt the air flow around the blades, preventing them from being lifted by the wind and damaged. The blades are 5m long, 0.5m wide, and have a mass of 50 kg. The blades are approximately symmetric airfoils (the engineer remembered that potential flow theory predicts that, prior to stall, the lift coefficient of a symmetric airfoil is approximately C = 2n sina). Assume that the center of lift and drag force is concentrated over the center of mass of the blade and that the leading edge is facing into the direction of the wind. p = 1.2 kg/m³. (a) Was there a reason to be concerned? At what wind speed will the blades be lifted by the wind, assuming that there is no drag? (b) If they are lifted by a 25 m/s wind, how fast will they be accelerated horizontally if the blade's lift to drag ratio, C,/C, = 0.03? The operating conditions found at two different points of a blade on a wind turbine are shown. These conditions were determined at a temperature for which the kinematic viscosity is 1.33 x 10$m²/s. What are the Reynolds numbers found at each blade section? Wind velocity (m/s) Angle of attack (degrees) Location (r/R) Chord (m) 0.15 15 1.5 0.95 75 0.35 7.5

Elements Of Electromagnetics
7th Edition
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Author:Sadiku, Matthew N. O.
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The blades of a wind turbine are ready to be installed on a turbine on top of a ridge.
The horizontal blades are supported at each end by saw horses, when a storm front
arrives. The turbine crew huddles in their truck as the rain starts and the wind picks up,
increasing eventually to 25 m/s. Realizing that the wind coming up the western slope
of the ridge roughly follows the 10° slope, the field engineer performs a quick
calculation and drives his truck upwind of the blades to disrupt the air flow around the
blades, preventing them from being lifted by the wind and damaged.
The blades are 5m long, 0.5m wide, and have a mass of 50 kg. The blades are
approximately symmetric airfoils (the engineer remembered that potential flow theory
predicts that, prior to stall, the lift coefficient of a symmetric airfoil is approximately C
= 2n sina). Assume that the center of lift and drag force is concentrated over the
center of mass of the blade and that the leading edge is facing into the direction of the
wind. p = 1.2 kg/m3.
(a) Was there a reason to be concerned? At what wind speed will the blades be lifted
by the wind, assuming that there is no drag?
(b) If they are lifted by a 25 m/s wind, how fast will they be accelerated horizontally if
the blade's lift to drag ratio, C/C, = 0.03?
The operating conditions found at two different points of a blade on a wind turbine are
shown. These conditions were determined at a temperature for which the kinematic
viscosity is 1.33 x 10-5m²/s. What are the Reynolds numbers found at each blade section?
Wind velocity
(m/s)
Angle of attack
(degrees)
Location (r/R)
Chord (m)
0.15
15
1.5
0.95
75
0.35
7.5
Transcribed Image Text:The blades of a wind turbine are ready to be installed on a turbine on top of a ridge. The horizontal blades are supported at each end by saw horses, when a storm front arrives. The turbine crew huddles in their truck as the rain starts and the wind picks up, increasing eventually to 25 m/s. Realizing that the wind coming up the western slope of the ridge roughly follows the 10° slope, the field engineer performs a quick calculation and drives his truck upwind of the blades to disrupt the air flow around the blades, preventing them from being lifted by the wind and damaged. The blades are 5m long, 0.5m wide, and have a mass of 50 kg. The blades are approximately symmetric airfoils (the engineer remembered that potential flow theory predicts that, prior to stall, the lift coefficient of a symmetric airfoil is approximately C = 2n sina). Assume that the center of lift and drag force is concentrated over the center of mass of the blade and that the leading edge is facing into the direction of the wind. p = 1.2 kg/m3. (a) Was there a reason to be concerned? At what wind speed will the blades be lifted by the wind, assuming that there is no drag? (b) If they are lifted by a 25 m/s wind, how fast will they be accelerated horizontally if the blade's lift to drag ratio, C/C, = 0.03? The operating conditions found at two different points of a blade on a wind turbine are shown. These conditions were determined at a temperature for which the kinematic viscosity is 1.33 x 10-5m²/s. What are the Reynolds numbers found at each blade section? Wind velocity (m/s) Angle of attack (degrees) Location (r/R) Chord (m) 0.15 15 1.5 0.95 75 0.35 7.5
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