Andreas Gawron asked 1 month 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 4 weeks ago
Hello,
The effective aoa includes the virtual twist when the viscous loop is activated.
André
Andreas Gawron answered 3 weeks 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 2 weeks ago Andre, thanks for the answer.