wave drag increase with number of sections

[jordi nosaurio]

Hello,

Maybe is the interpretation of the CD0_w of the wave drag tool. But values change drastically with the number of slices. For example for a typical fuselage/wing aircraft:

5 slices,    CD0_w = 0.034

20slices,   CD0_w = 0.15

100slices, CD0_w = 2.61

Any clues?

thank you!

jorge

[Rob McDonald]

You should go back through the Workshop videos and watch one of the presentations on the Wave Drag tool.  I talk about the appropriate number of slices in those presentations, but you need the video version, not just the slides.

Due to the formulation of the wave drag tool, the drag will always increase as the number of slices is increased.

What you are seeing with 100 slices is too much.  If you gradually increase the number of slices, you will see more reasonable behavior before things possibly go singular (as they appear to have for the 100 slices).

It is impossible to know how many slices you need without knowing your geometry.

Rob

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[jordi nosaurio]

Wow Rob, thank you for the quick response!. I will search for the video. 100 slices was just a numerical test, definitely was diverging and I did not know why.

[jordi nosaurio]

Perfectly explained:

https://www.youtube.com/watch?v=cMnwNCI28Ko&list=FL17bvi551qX9zqLkoa-Vj5Q&index=1&t=850s

"Lets say the fewer points the better (but trying to capture the area distribution)"