# Theretical aspects of the non-planar DOUBLET LATTICE METHOD

1. Jul 25, 2006

### traianus

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?

2. Jul 26, 2006

### Danger

Could you possibly keep your title down to a dull roar? That hurt my head.

3. Jul 26, 2006

### traianus

My topic was not about the title of it...
So please post messages related to the topic.

4. Jul 27, 2006

### Danger

Yes, Sir, Sir. My humble apologies. I had totally forgotten that you own this site.

5. Jul 27, 2006

### traianus

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.

6. Nov 7, 2008

### ant2008

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.