how to calculate cd  drag coefficient??????
Hi, I have simulated the flow over an aerospace vehicle. Now I can get the drag force on the surface of the vehicle(with the help of readymade options that are available in CFXpost). I know that, cd = drag force / (dynamic pre * reference area). Whatever the cd that I have obtained is being half of the exact value. I am not getting the mistake. Plz help. Thank you.

Re: how to calculate cd  drag coefficient??????
OK, quick question, have you used a symmetry plane? If so, then you have to double the force. Stu

Re: how to calculate cd  drag coefficient??????
Remember this computing task list: <Li> Lift is easy[*] Drag is hard[*] Moment is imposibble
 Michael 
Re: how to calculate cd  drag coefficient??????
Hi I have obtained for a 3D wing a good results even for Cm Coeff. However its difficult to compare it to other methods since every numeric method has serious problems with moments.

Re: how to calculate cd  drag coefficient??????
Check your reference area value

Re: how to calculate cd  drag coefficient??????
Hi,
Yes, check your reference area; but also most people calculate drag from Cd = D / (A * .5 * rho * V^2) (http://www.grc.nasa.gov/WWW/K12/airplane/dragco.html) and that has a factor of 2 in it. If you left it out you would be out by exact 2! Maybe that's it. Regards, Glenn Horrocks 
Re: how to calculate cd  drag coefficient??????
Thanks to all. I obtained the results.

All times are GMT 4. The time now is 05:57. 