11111110
ES330 Section 2
Midterm Exam #2
Name:
You will have 1.25 hours to complete the exam. Please show all work and list any
assumptions that you are making in the solution. You must draw a control volume, free
body diagram, and coordinate system if required by the problem to receive credit for your
work.
1. (35
points total)
The power, P
(Nm/s),
of a wind turbine is dependent on the rotor
radius, r (m), the blade rotational speed
Ct.)
(rad/s),
the wind speed V
(mls),
and the fluid
properties p
(Ns2/m4)
and !l
(Ns/m\
Note for air: p=1.2
(Ns2/m4)
and !l=1.789x 10
5
(Ns/m2)
(a)
(15
points)
Find the nondimensional groups for this problem. Use r, V, and p as the
repeating variables.
(b)
(10
A wind turbine has a radius of 2 m. The rotational speed is 20 rpm for a
wind speed of 5
mls.
If
the wind turbine is tested in at a
1110
scale in a wind tunnel
what is the flow speed needed for the test?
(c) (5
What is the rotational speed of the blades for the model wind turbine?
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 Spring '09
 ACHUTHAN
 Fluid Dynamics, Velocity, ind turbine

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