Don't worry, I didn't really answer anything
I do think that a Cd of 0.02 is possible. I think that if the duct is designed properly, the exit flow should come close to the freestream airflow. Any difference in speed will show up as drag.
Here are the symbols I used above:
cd = coefficient of drag
cd,i = coefficient of induced drag
cd,w = coefficient of wave drag
cd,p = coefficient of form drag
cd,f = coefficient of skin friction
Cl = coefficient of lift
Cp = coefficient of pressure
p = pressure at body surface
p∞ = freestream pressure
q∞ = dynamic pressure (1/2 rho V^2)
rho = air density
S = planform area
A = front plate area
pi = 3.14159
e = oswalds efficiency factor (based on lift distribution)
AR = aspect ratio (b^2/S)
b = wingspan
Df = drag force
Any questions?
I have plenty...where's trebuchet03 when you need him...
- LostCause