Theretical aspects of the non-planar DOUBLET LATTICE METHOD

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Discussion Overview

The discussion revolves around the theoretical aspects of the doublet lattice method applied to non-planar surfaces, specifically addressing questions related to dihedral angles and symmetry boundary conditions in the context of programming a doublet lattice code. The scope includes technical explanations and mathematical reasoning.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant inquires about the measurement of the dihedral angle in relation to a wing with positive dihedral, questioning whether it remains the same or changes based on the symmetry plane.
  • The same participant seeks clarification on how to impose symmetry boundary conditions in their doublet lattice code, particularly in relation to the dihedral angle.
  • Another participant shares their experience, stating they programmed their code using a specific approach to the dihedral angle and boundary conditions, noting that it functions correctly.
  • This participant also references a text by Max Blair, asking if others have run a specific example and what results they obtained.

Areas of Agreement / Disagreement

Participants express differing views on the measurement of the dihedral angle and the implementation of boundary conditions, indicating that multiple competing perspectives remain without consensus on these technical aspects.

Contextual Notes

There are unresolved questions regarding the assumptions behind the dihedral angle measurement and the specifics of symmetry boundary conditions, which may depend on the definitions used in the programming context.

traianus
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Hello,
I have been programming a doublet lattice code for nonplanar surfaces with zero thickness. I have some questions about LANDAHL's formulation.

1) How the dihedral angle is measured? This question may appear silly, but please explain. Suppose to have a wing with positive dihedral (let's say 3DEG). Suppose that the plane y-z is a symmetry plane. In the negative portion, is the dihedral still 3 DEG (in the mathematical formulation of the kernel) or 180-3 DEG (measured from + y)?

2) Connected to 1) how do I impose the symmetry boundary conditions? I was doing so by using a symmetric doublet for each sending panel, but then I did not know how to consider the dihedral (see previous question). Anybody knows?
 
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Could you possibly keep your title down to a dull roar? That hurt my head.
 
My topic was not about the title of it...
So please post messages related to the topic.
 
Yes, Sir, Sir. My humble apologies. I had totally forgotten that you own this site.
 
The moderators should do something about it. This is not a serious forum. I asked a serious question about an interesting topic and your best shot is to talk about the title? If the moderators do not solve the problem and a person like "Danger" comes to offend people then the forum is not worth it. If I do not see actions I will leave forever and delete all my posts. If you feel happy about that it is fine to me.

Bye.
 
Hi, traianus. If it is still of any use, I have programmed my doublet lattice code using 180-(angle of positive portion) DEG in the negative portion, and it works. I also used boundary conditions with oposite signs in the positive and negative portions, in the case of physically symmetric boundary conditions, and with the same signs, in the case of antisymmetric conditions. This means I invert the sign of the real displacements on the negative portion. Because the normals to the panels have opposite signs in opposite portions.

But now, please, regarding the text from Max Blair, "A compilation of the mathematics leading to the doublet-lattice method", have you run the example from pages 113-114, for the reduced frequency of 1.4? Which results have you obtained?

Thank you.
 

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