1. You want to find the wind drag on a new automobile design at various speeds. To do this, you test a 1/30 scale model

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1 You Want To Find The Wind Drag On A New Automobile Design At Various Speeds To Do This You Test A 1 30 Scale Model 1 (58.63 KiB) Viewed 48 times

1. You want to find the wind drag on a new automobile design at various speeds. To do this, you test a 1/30 scale model of the car in the lab. You must design an experiment whereby the drag force measured in the lab can be scaled up directly to find the force on the full- scale car at a given speed. a. What is the minimum number of dimensionless variables required to completely define the relationship between all the important variables in the problem? Derive an expression for drag force Fp using the Buckingham Pi method (e.g. 11 = f(T2, 113...)). The following table is provided for your convenience: Variable Symbol Units Dimensions Drag force FD kg-m/s2 Speed Length of automobile L Fluid density kg/m3 Fluid viscosity р kg/m-s Hint: use L, V and p as your core group variables, therefore making sure to isolate Fp in the analysis. b. The only fluids you have available in the lab are air and water. Could you use either one of these, if you wanted to? Determine what the velocity of these fluids past the model car would have to be so that the experiment would simulate the drag on the full-scale car at 40 mph. V m/s P