What is 'CDtott' in vspaero result

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Inseo Choi

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Jul 26, 2022, 10:16:52 PM7/26/22
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VSPAERO drag coefficient list is,

until 3.28.0
CDi
CDo
CDt
CDtot

Now 3.29.0,
'CDtott' is new value of drag coefficient.

I always use Total CD value from 'CDtot', but now 'CDtott' is new value.

What 'CDtott' means ?

Rob McDonald

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Jul 27, 2022, 12:15:32 AM7/27/22
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CDi and CDt are the same physical quantity (induced drag) -- but calculated with different methods.  They should generally be a pretty good match for each other.

CDo is the parasite drag estimate

CDtot = CDi + CDo
CDtott = CDt + CDo

Rob


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Inseo Choi

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Jul 28, 2022, 11:13:47 AM7/28/22
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Thank you Rob.

But Cdtot and Cdtott are show different value of Total CD

This is Ly1.VSP and Ly.csv.

What Total CD should I use?

-Inseo-
2022년 7월 27일 수요일 오후 1시 15분 32초 UTC+9에 Rob McDonald님이 작성:
Ly1.csv
Ly1.vsp3

Rob McDonald

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Jul 28, 2022, 11:26:32 AM7/28/22
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You should use CDi and CDtot.  CDt and CDtott should be treated as diagnostics for the developers.

Your model has inadequate chordwise resolution -- and too much LE clustering.  For VLM, the natural curvature of the LE creates additional clustering.

I would change clustering to be 0.25 at both the LE and TE and then substantially increase the chordwise resolution.

Rob


Inseo Choi

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Jul 28, 2022, 8:49:03 PM7/28/22
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Thank you Rob.


2022년 7월 29일 금요일 오전 12시 26분 32초 UTC+9에 Rob McDonald님이 작성:

Ferran Marti

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Jul 29, 2022, 10:47:27 AM7/29/22
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It seems to be due to the Actuator Disk. A wing only has a good match of CDi and CDt
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