A laminar flow wind tunnel has a test is 30cm in diameter and 80 cm length. The air is at
Answer: Approx 6%
The center line air speed acceleration at the end of the test section.
Answer to Problem 90P
The center line air speed acceleration at the end of the test section is
Explanation of Solution
Given information:
The diameter of the wind tunnel is
Write the expression for the Reynolds number at the end of the test section.
Here, the velocity of the air is
Write the expression for the increase the velocity by equation of continuity.
Here, the area at the beginning of the test section is
Write the expression for the area at beginning.
Here, the diameter of the wind tunnel is
Write the expression for the area at the end of the test section.
Here, the displacement thickness is
Write the expression for displacement thickness.
Write the expression for the velocity increment.
Write the expression for the percentage of velocity increase at the end if the test section.
Write the expression for the radius of the wind tunnel.
Here, the diameter of the wind tunnel is
Calculation:
Refer to the Table A-9 "properties of air" to obtain the value of kinematic viscosity
Substitute
The value of Reynolds number is less than
Substitute
Substitute
Substitute
Substitute
Substitute
Substitute
Substitute
Conclusion:
The center line air speed acceleration at the end of the test section is
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