Andreas Gawron asked 10 months ago
In case of performing a type 2 polar analysis the angle-of-attack (aoa), I call it here the AoA_geometrical, is running for alaysis between a min and max value. Due to the downwash, induced angle, and twist angle the effective AoA should be:
AoA_effective = AoA_geometrical + AoA_induced + AoA_twist
I assume AoA_effective is indicated in the “aoa+ai+twist” vs. y graph in the operating point view. Therefore my question: What is then the “effective aoa” vs. y graph, also in the operating point view, indicating?
techwinder Staff answered 10 months ago
Hello,
The effective aoa includes the virtual twist when the viscous loop is activated.
André
Andreas Gawron answered 9 months ago
Andre, thanks for you answer. But I am still confused. I have understood, that the virtual twist is calculated in a polar type 6 analysis. But I can not select type 6 in the “Analysis definition”. I am using a type 2 analysis. I am running Analysis => Batch analysis (1). There it is possible to “Enable viscous loop”. I have performed the type 2 analysis with and without activating “Enable viscous loop”. In both cases the results are exactly the same. The graphs “aoa+ai+twist” are the same for both cases. The same applies for the graphs “effective aoa” and “virtuel twist”. “virtual twist” is always zero. “aoa+ai+twist” and “effective aoa” are different. Therefore I still ask myself what the AoA_effective for my airplane under investigation is and what the difference between “aoa+ai+twist” and “effective aoa” is. Where is my comprehension problem?
To define a T6 analysis, use Ctrl+F6 instead of F6. Then the viscous loop option should become active.
That being said, the viscous loop is not as important an improvement as I thought it would be when I launched flow5, so you can safely ignore it.
If you do not activate the viscous loop, just ignore the “effective aoa” which is of no interest; for information, its definition is
alpha_0 + (Cl/2 pi) – Virtual_Twist.
André
Andreas Gawron
replied 9 months ago Andre, thanks for the answer.