# You are to conduct wind tunnel testing of a new football design that has a smaller lace height than previous designs. It is known that you will need to maintain a Re and St similarity for the testing. Based on standard college quarterbacks, the prototype parameters are set at V = 40 mph and ω = 300 rpm, where V and ω are the speed and angular velocity of the football. Theprototype football has a 7 in. diameter. Due to instrumentation required to measure pressure and shear stress on the surface of the football, the model will require a length scale of 2:1 (the model will be larger than the prototype). Determine the required model freestream velocity and modelangular velocity. [Answer in units of mph and rpm].

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You are to conduct wind tunnel testing of a new football design that has a smaller lace height than previous designs. It is known that you will need to maintain a Re and St similarity for the testing. Based on standard college quarterbacks, the prototype parameters are set at V = 40 mph and ω = 300 rpm, where V and ω are the speed and angular velocity of the football. The
prototype football has a 7 in. diameter. Due to instrumentation required to measure pressure and shear stress on the surface of the football, the model will require a length scale of 2:1 (the model will be larger than the prototype). Determine the required model freestream velocity and model
angular velocity. [Answer in units of mph and rpm].
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Step 1

Determine the length scale ratio of model prototype;

Step 2

For same air conditions:

Determine the required model free stream velocity using the formula;

Step 3

Determine the angular velocity of the model using the Strou...

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### Civil Engineering 