On July 27 Ford donated valuable wind tunnel time that allowed the team to accurately characterize the aerodynamics of Arcturus. Ford has been supporting our team for over a decade: Tesseract, Eleanor, Chopper del Sol, and now Arcturus have all been tested at Ford’s wind tunnel facilities. Ford’s Driveability Test Facility is in Detroit, MI, which is 798 miles from our shop. So we made the 15 hour drive out there with the goal of determining the aerodynamic properties of Arcturus. The most important of these is the power loss caused by drag, which is described by the equation below. P is power lost; ρ is the air density; v is the velocity of the car; A is the frontal area of the car; and Cd is the coefficient of drag.

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The frontal area and the coefficient of drag must be found experimentally. To determine Arcturus’s frontal area, Ford projected a large LASER over the car onto a screen. The dark areas on the screen can then be integrated to find the frontal area.


At first yarn tufts taped to car were used to visualize air streams at the surface of the car while the wind tunnel was running.

To characterize the coefficient of drag, the drag on the car was measured at various air speeds and angles (since C will change with wind direction).  At cruising speed Arcturus has approximately the same amount of drag as sticking your hand out the window on the highway.  

Smoke was then used to visualize airflow above the car’s surface.

 

Pictures from the day: