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Is the co-efficient of drag related to how much of the front profile actually catches air dead on instead of deflecting it in one direction or another? To be more specific, can it safely be assumed that a flat-faced RV has a cd of 1.0?
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No.... Allow me to explain each component of the drag equation - you don't need to use it, but knowing what each bit does isn't math and explains much.
Fd is the drag force - the thing we're calculating
rho (that p looking thing) represent the density of the flowing fluid, in our case - air
v is the velocity
A is the frontal area, I'll explain more in a moment
Cd is the drag coefficient - it is a unit less number that must be experimentally determined.
that v with the hat is the unit direction
Frontal Area
Basically put, it's the area that's in the way. For your car, if you were to take a picture of the front and measure the area - that would be the frontal area if we assume no cross winds. If your car is parked, and there's 15mph pure cross wind - the "frontal" area would be the area of the side of your car.
Cd
Cd is a phenomena - which means it's observable but beyond intuition. One really can't guess the Cd of an object. Think of Cd as the form constant - the shape (not size) will change the value of Cd. And Cd can be greater than 1.
A few things to note
1. A change in velocity increases force exponentially
2. A reduction in A is just as effective as an equivalent reduction in Cd
3. Rho will be dependent on the environment - altitude, temperature, humidity (even rain).
4. The negative sign comes from that v with a hat, because drag force is opposing the direction of motion.
Here's some selected Cd values for you
