Wave Drag vs Parasitic Drag Tool

[Jones]

I noticed that the wave drag tool displays the CD0_w and not the delta CD0_w. Does the wave drag calculation compute total drag at supersonic speeds (including parasitic and induced drag), or is it only computing the wave drag?

Additionally, if it does only compute wave drag, how can you compute parasitic and induced drag at supersonic speeds if the parasitic drag tool only works for subsonic speeds? (Saw in python code it said to only use parasitic drag tool for subsonic).

Thanks for the help! I am very new to OpenVSP but have really enjoyed learning the software and all of the awesome capabilities it has!

[Rob McDonald]

The Wave drag tool output is wave drag only.

The parasite drag tool is fine for supersonic speeds.  I'm not sure why someone put the note in the Python code otherwise.

VSPAERO thin-surface mode can be used to calculate supersonic induced drag.

Rob

[Jones]

Rob,

Thank you for sharing this info. That is incredibly helpful info regarding parasitic and induced drag as well.

Your support of the members of this community and such quick and meaningful help is awesome.

[Brian Davis]

Hi Rob,

Re: "The parasite drag tool is fine for supersonic speeds.  I'm not sure why someone put the note in the Python code otherwise."

I have been debugging high viscous drag coming from the parasite drag tool at supersonic speeds. The default turbulent method is "Schlichting Compressible" (Cf = 0.455 / log(Re)^2.58), however it seems the compressibility correction (for supersonic speeds) is not applied or used. I do not see it in the source code. This would lead to a significant overestimation of the skin friction coefficient with the error increasing with Mach number. 

I've attached equations/plots taken from Nicolai and Torenbeek for reference.

Brian