Correlation of results on wing performace


#1

https://www.simscale.com/projects/krausd/vtol_wingonly/

Hi
here is my project of flying wing, I try to compare solution with another SW (XFLR5 - specialised for air-plane design) and i get quite different solutions.

AOA 3° airspeed 20m/s
XFLR5 full wing drag 3,3N lift 97N
SIMSCale half wing drag3.3N lift 70N

So it looks like solution from Simscale is almost double of XFLR5 solution, which I believe shut be quite close to reality.

Do you see some misstates what I made? Thanks for advice.
David


#2

Hi @krausd!

Do you have any resource for the validation that you can share to see what assumptions have been made for this case? On top of that I think that you have to extend the region behind the wing and not have such a big region in front of it.

Additionally I do not see how any value is double the XFLR5 value. Can you please elaborate or did you just make a typo?

Cheers,

Jousef


#3

Hi
I use XFLR on other project and results looks OK, it is a bit simpler SW and I have more experience so probability of wrong setting is lower

values are almost twice different because results from XFLR is for full wing but from SimScale for half-wing, to have more clear
XFLR5 drag 3,3N lift 97N
SIMSCale drag 6.6N lift 140N

I try to change mash as you advice
Best regards
David


#4

Hi David (@krausd)!

I saw that you did not use any boundary layer for your airfoil but used yplus as a result control item. If you are using wall functions, yplus does not need to be in the vicinity of 1 but should be within the range of 30 to 300. If you are higher than this that would result in unrealistic friction drag values. Maybe you check that first to make sure this is not an error source because I think that this might be a major reason for your big difference. Is the value for the XFLR5 a literature value or did you just assume that is is approximately correct?

Cheers!

Jousef