SimScale CAE Forum

How do I get the values of (cp vs x / c graph) in a fuselage


#1

Hello everyone,

I’m analyzing a fuselage in cfd and would like to know how can I get the values ​​of (cp vs x / c graph) at an angle of zero degrees to compare with other fuselages and even an airfoil? And how can I also change the angle of attack of the fuselage to get the results of cl vs alpha?

thank you
Jeferson Martins


#2

Hi Jeferson (@j_martins),

Thanks for you question and welcome :slight_smile: . @1318980, do you have any experience with this?


#3

Hi @j_martins, thanks for tagging me @AnnaFless.

To get Cp v x/c we need to do a bit of offline post processing.

The steps I used (off the top of my head):

  • Download the results
  • Open in ParaView
  • Create a calculator filter and call it Cp
  • do the calculation Cp = (p-p(freestream)/(rho(freestream)*V(freestream)^2)
  • You should now have a result field for Cp
  • Extract surface (for an aerofoil I did this twice one for upper and one for lower)
  • Slice the surface at the position you want to create your 2D data lines for Cp
  • Export as a CSV
  • Open in excel and readjust the position to range from 0-1 (x/c)
  • plot the data

I can remember, but I think you get 3D coordinates. You just need to take the ordinates in the direction of the cord if that makes sense.

I haven’t personally taken this to create Cl, however, if you multiply it by the generate surface normals then either sum or integrate you can get Cl (there is a youtube video on this I think :smiley: )

There is no easy way to do this for all your results but you should be able to save the state and reopen it with new data (one for each AoA).

As for changing AoA for you simulations if you don’t need to ramp the velocity you can define an inlet outlet or free stream boundary condition and simply change the component velocities to get the different AoA’s.

If I missed anything here, or if you have any further questions just ask!
Darren


#4

Hi @AnnaFless

I’m student of aerospace Engineering and i need this information because my initiation research is about the possibility aerodynamics on shark body, and i don’t know how can I get the values.
Thanks for the indication of 1318980.

Jeferson Martins