[Gridgen] Blocking topology for blunt wing

siw · July 20, 2010, 04:04

Hi,

I need to generate a multiblock structured mesh using Gridgen version 15.13 (the newest version at university) of a 3-D wing where the root of the wing is attached to a fluid domain face (just like a wing attached to a wind tunnel wall).

The wing has a constant aerofoil profile along the span but it does taper (but there's no twist or dihedral angles). The trailing edge is blunt (about 1 mm thick) and the wing tip is also blunt (there's no rounding or blending of the wing tip). I'm considering 2 wings: one with a rearward swept angle and another with a forward sweep angle.

What would be the best blocking topology for such a wing, considering the blunted trailing egde and wing tip?

Thanks

MrCFD · July 20, 2010, 18:42

Are you looking to resolve boundary layer flow?

siw · July 21, 2010, 07:37

Hi,

I was considering making a series of meshes of various element quantities to make sure I get a mesh independent solution, but I was not going to try different fluid domain sizes. As part of that I was going to alter the first layer height from the surfaces, this height will be based on the y+ value. I was considering y+ = 1, 11, 100 to cover the viscous sublayer, the buffer layer and the log-law-of-the-wall layer.

MrCFD · July 21, 2010, 14:55

I have not had much luck using structured grids in Gridgen simply because the wings which I have been working with are very complex, variable airfoil sections, twist, sweep, taper... the works.

But I have seen a structured block topology which could work. Defining boundary conditions may present a problem though.

If you recall the 2-D airfoil tutorial in Gridgen it walks you through the extrusion of a structured mesh from the airfoil and a connector extending to the rear. If you can create a blended end cap or a fillet at the end cap, you should be able to define the whole wing and another mesh extending to the rear with a couple of surface meshes.

Something like this: (bear with the crudeness)
_________
\ \_______|
.\_\______|

2 surface meshes and 7 connectors.

2 connectors at wing root, 1 at the end-cap/tip, 1 at the trailing edge, and the remaining 3 make up the edges of the downstream mesh.

The mesh over the wing loops from the trailing edge over to the leading edge and back. You should then be able to extrude a block in a fashion similar to the mesh extrusion seen in the tutorial with initial delta-s specified to achieve your desired Y+.

I hope this helps.

July 20, 2010, 04:04	[Gridgen] Blocking topology for blunt wing	#1
siw Senior Member Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 742 Rep Power: 26	Hi, I need to generate a multiblock structured mesh using Gridgen version 15.13 (the newest version at university) of a 3-D wing where the root of the wing is attached to a fluid domain face (just like a wing attached to a wind tunnel wall). The wing has a constant aerofoil profile along the span but it does taper (but there's no twist or dihedral angles). The trailing edge is blunt (about 1 mm thick) and the wing tip is also blunt (there's no rounding or blending of the wing tip). I'm considering 2 wings: one with a rearward swept angle and another with a forward sweep angle. What would be the best blocking topology for such a wing, considering the blunted trailing egde and wing tip? Thanks

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July 20, 2010, 18:42		#2
MrCFD New Member Anonymous Join Date: Nov 2009 Posts: 4 Rep Power: 17	Are you looking to resolve boundary layer flow?

July 21, 2010, 07:37		#3
siw Senior Member Stuart Join Date: Jul 2009 Location: Portsmouth, England Posts: 742 Rep Power: 26	Hi, I was considering making a series of meshes of various element quantities to make sure I get a mesh independent solution, but I was not going to try different fluid domain sizes. As part of that I was going to alter the first layer height from the surfaces, this height will be based on the y+ value. I was considering y+ = 1, 11, 100 to cover the viscous sublayer, the buffer layer and the log-law-of-the-wall layer.

July 21, 2010, 14:55		#4
MrCFD New Member Anonymous Join Date: Nov 2009 Posts: 4 Rep Power: 17	I have not had much luck using structured grids in Gridgen simply because the wings which I have been working with are very complex, variable airfoil sections, twist, sweep, taper... the works. But I have seen a structured block topology which could work. Defining boundary conditions may present a problem though. If you recall the 2-D airfoil tutorial in Gridgen it walks you through the extrusion of a structured mesh from the airfoil and a connector extending to the rear. If you can create a blended end cap or a fillet at the end cap, you should be able to define the whole wing and another mesh extending to the rear with a couple of surface meshes. Something like this: (bear with the crudeness) _________ \ \_______\| .\_\______\| 2 surface meshes and 7 connectors. 2 connectors at wing root, 1 at the end-cap/tip, 1 at the trailing edge, and the remaining 3 make up the edges of the downstream mesh. The mesh over the wing loops from the trailing edge over to the leading edge and back. You should then be able to extrude a block in a fashion similar to the mesh extrusion seen in the tutorial with initial delta-s specified to achieve your desired Y+. I hope this helps.