A car model has a length of 10.2 ft, a width of 5.1 ft and a height of 5.1 ft an

Question

A car model has a length of 10.2 ft, a width of 5.1 ft and a height of 5.1 ft and it is placed in the wind tunnel for testing as shown. Air flow at 60?F with a density of 0.00237 slug/ft^3 and a velocity of 130.2 ft/s passes over the car. Find the horse power that the car model consumed

Flow Reynolds number is found to be 4.2x10^5

What is the best way to define system to solve this problem?

           A) Define tunnel as the system

           B) Define the car as the system

Is the flow external or internal for the system you defined in question (1)?

        A) External flow

        B) Internal Flow

Is the flow laminar or turbulent if the flow Re = 4.2x10^5

       A) Laminar

       B) Turbulent

The drag coefficient or the friction factor is most nearly?

       A) 1.18

       B) 0.87

       C) 0.39

The horse power the car model consumed is most nearly?

           A) 145.3 hp

          B) 107.12 hp

          C) 48.02 hp

Without actual calculation, what is the approximate percentage of the pressure drag out of total drag on the car according to the car geometry?

      A) 100%

      B) 80%

      C) 50%

      D) 20%

      E) 0%

Explanation / Answer

What is the best way to define system to solve this problem?

           A) Define tunnel as the system

As the whole energy can be conserved

Is the flow external or internal for the system you defined in question (1)?

        B) Internal Flow

It's quite obvious

Is the flow laminar or turbulent if the flow Re = 4.2x10^5

       A) Laminar

I have done the calculations but if you want to see them you might need to give me more points !!

The drag coefficient or the friction factor is most nearly?

       B) 0.87

I have done the calculations but if you want to see them you might need to give me more points !!

The horse power the car model consumed is most nearly?11

           A) 145.3 hp

I have done the calculations but if you want to see them you might need to give me more points !!

Without actual calculation, what is the approximate percentage of the pressure drag out of total drag on the car according to the car geometry?

      D) 20%

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