Calculating Drag Coefficients for DC-10 in Cruise

  • Thread starter Thread starter angelwings
  • Start date Start date
  • Tags Tags
    Drag
AI Thread Summary
Calculating drag coefficients for a DC-10 in cruise involves using specific formulas and data, including thrust, density, velocity, weight, aspect ratio, and wing area. The provided thrust of 153,000 lb is appropriate for three engines, while the wing area of 3,958 ft² seems unusually large, prompting questions about its accuracy. The formulas for drag coefficients (Cd, Cdi, and CDo) appear correct, but discrepancies in calculated values suggest potential issues with data or unit conversions. Dimensional analysis has been performed, yet confusion remains about the Oswald efficiency factor's suitability for the DC-10. Accurate calculations and graphing assistance are sought to clarify these drag coefficient values.
angelwings
Messages
3
Reaction score
0
i am having trouble calculating various drag co-efficents for a dc -10 in cruise.

i have found this data:
Thrust: 153000 lb
density: 0.00085 slug/ft
V= 852ft/s
W=580000lb
AR= 7.5
e= .8
S= 3958ft^2
Cl= 0.5

I have also found the formulas
Cd= D/ (density x S x V^2 /2)
Cd= Cdo + ((cl^2) / (pi x AR x e))
Cdi= (cl^2)/ (pi x AR x e)

i have tried these but get odd answers. i need help to know whether my mistake is my data, my formulas or my calculation.
help with graphing this data vs airspeed would also be appriciated
cheers
 
Physics news on Phys.org
It appears that you have all the information you need to do the calcs. Perhaps it is a units issue? If you show us what you have we might be able to pinpoint something for you.
 
Is that value for S right?

It looks rather large indeed, but then I'm too snobby to work in imperial units to find out for sure.
 
the answers that i got using these formulas were:
for Cd = 0.125
for Cdi= 0.0137
for CDo = 0.11
as cdi and cdo were so different i thought that there must be a problem.
i was also unsure if the thrust value given was for one engine or for all three. is it an appropriate value for three engines?

-in response to brewnog S= 317 m ^2
 
The thrust value you give is consistent with three engines. 50,000 Lbf sounds about right for a single engine.

Did you do a dimensional analysis to make sure your units were all canceled out?
 
i did a dimensional analysis. but I'm pretty sure that I'm using all the right units. still having problems though. are the formulas correct and is the oswald efficency factor an approptriate value for a DC - 10?
 
Back
Top