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Wind Tunnel Aerodynamics Answers

The wind tunnel test section (A), as in some operating wind tunnels, can be resized by moving the walls, ceiling and or floor to give a different cross-sectional area. The other 2 sections B and C are not adjustable. Give all answers to the nearest hundredth.

  1. The measured velocity in the rectangular test section (A) is 10 m/sec. The initial dimensions of the test section are 3 m high and 4 m wide.
    1. What is the cross-sectional area (A)?12 m2
    2. What is the constant (V x A)? 120 m3/sec.
    3. What cross-sectional area (A) will I need to double the Velocity? 6 m2
    4. What cross-sectional area (A) will I need to decrease the Velocity fourfold? 48 m2
    5. What would the Velocity be if I changed the dimensions to 6 m high and 4 m wide? 5 m/sec.
    6. What would the Velocity be if I changed the dimensions to 5 m high and 5 m wide? 4.8 m/sec.

     

  2. Assume that the wind tunnel test section (A) is triangular. Our initial velocity is still 10 m/sec.
    1. What is the formula for the area of a triangular cross-section? A = 1/2 bh
    2. The triangular test section has a base of 5 m and a height of 4 m. What is the Area(A)? 10 m2
    3. What is the constant (V x A)? 100 m3/sec.
    4. What cross-sectional area (A) will I need to double the velocity? 5 m2
    5. Give a base and height measurement which would result in the cross-sectional area in 2d. b/h = 2/5, 1/10, 2.5/4 etc.
    6. What would the velocity be if I changed the dimensions to a base of 8 m and a height of 10 m? 2.5 m/sec.

     

  3. The fan exit section (B) is circular in shape. The initial velocity is again 10 m/sec.
    1. What is the formula for the area of a circular cross-section? A = IIr2
    2. The cross-sectional area of B is 20 sq. m. What is the radius? 2.52 m
    3. What is the constant (V x A)? 200 m3/sec.
    4. If I rebuilt this section, what radius would be required to generate a velocity of 50 m/sec.? 1.13 m

     

  4. The cross-sectional areas of Test Section (A), Fan Exit Section (B), and Section C are 20, 60 and 100 m respectively. The velocity at B, the Fan Exit Section, is 50 m/sec.
    1. What is the constant (V x A)? 3000 m3/sec.
    2. What is the Velocity at cross section C? 30 m/sec.
    3. What is the Velocity at Test Section A? 150 m/sec.
Please send any comments to:
Curator: Tom.Benson@grc.nasa.gov
Responsible Official: Kathy.Zona@grc.nasa.gov