Repeat the calculation of Prob. 10-90, except for a test section of square rather than round cross section, with a
The center line air speed acceleration at the end of the test section.
Answer to Problem 91P
The center line air speed acceleration at the end of the test section is
Explanation of Solution
Given information:
The side 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 side of the 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.
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
Substituting
Conclusion:
The center line air speed acceleration at the end of the test section is
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