[Far]

give me boundary conditions

[James Hetfield]

boundary conditions:
1-CURVES ----> wall
2-INLET -----> velocity inlet: velocity = 90 for zero angle of attack in X-direction (it can be found for other angles of attack)
3-OUTLET ----> pressure outlet (atmosphere pressure)

[Far]

can you show the convergence plot. whats the mach no. for this simulation?

[James Hetfield]

what do u mean?
I just set the velocity at INLET and the fluid is air "density=ideal gas, viscosity=sutherland"

[James Hetfield]

there is no option to set Mach No.

[E63 AMG]

The outer boundary shall be modeled using Farfield BC. And, ofcourse you need Mach no for this.

There was tutorial on NACA 0012 Airfoil, with some AoA, using Fluent. You shall go through that for reference.

Originally Posted by James Hetfield

what do u mean?
I just set the velocity at INLET and the fluid is air "density=ideal gas, viscosity=sutherland"

[James Hetfield]

what is the difference if I use INLET and OUTLET boundary conditions instead of farfield?

[E63 AMG]

To quote from FLUENT Manual:

Velocity Inlet BC:
" In this case, the total (or stagnation) pressure is not fixed but will rise (in response to the computed static pressure) to whatever value is necessary to provide the prescribed velocity distribution.

This boundary condition is intended for incompressible flows, and its use in compressible flows will lead to a nonphysical result because it allows stagnation conditions to float to any level. "

Based on the information provided in the thread, I had assumed that you are trying to solve the compressible flow problem. In the external flow problems, the stagnation properties remain constant.

Kindly refer to FLUENT Manual for selecting appropriate BC for the simulations.

Hope this helps for your project.

[Ralen]

Originally Posted by Far

check this mesh

How do you associate green edges to the curves of the wing? So, the edges coincide with the curves of the wing?

[James Hetfield]

you're da man!
thanks
Im doing Compressible (Air, density=ideal gas, viscosity=sutherland)

Originally Posted by E63 AMG

To quote from FLUENT Manual:

Velocity Inlet BC:
" In this case, the total (or stagnation) pressure is not fixed but will rise (in response to the computed static pressure) to whatever value is necessary to provide the prescribed velocity distribution.

This boundary condition is intended for incompressible flows, and its use in compressible flows will lead to a nonphysical result because it allows stagnation conditions to float to any level. "

Based on the information provided in the thread, I had assumed that you are trying to solve the compressible flow problem. In the external flow problems, the stagnation properties remain constant.

Kindly refer to FLUENT Manual for selecting appropriate BC for the simulations.

Hope this helps for your project.

[James Hetfield]

I use Edit Edge-->Automatic Linear, exactly as Simon says in his tutorial

how am I supposed to do that? any better ideas? how about the leading edge facet?

Originally Posted by Ralen

How do you associate green edges to the curves of the wing? So, the edges coincide with the curves of the wing?

[aptahaney]

Originally Posted by Far

check this mesh

Hi, I know this thread is old but I was hoping someone could provide me with a bit of insight, as I am also having difficulty with the validation of the NACA airfoil. I have been at it for months and I just seem to be getting nowhere.

I created a mesh in ICEM, based on Far's mesh example (in this thread) using the same sections, and number of nodes where I could. (I had to reduce it slightly as I needed to reduce the node quantities). I'm using the same domain shape as shown here, http://turbmodels.larc.nasa.gov/naca0012_val.html, but at a distance of 50 chord lengths.

I then ran this program using Realizable k-e, ideal gas, wind speed 87.64m/s (mach number 0.26), angle 8 degrees,
Boundary Conditions:
Inlet = velocity inlet
Upper & Lower Surfaces = velocity inlet
Outlet = Pressure far-field

However, I got a graph that will not converge, and in which the continuity equation value is actually increasing..... despite the fact that I followed Far's helpful model, as best as I could.

Can any one suggest where I may be going wrong on this? Is there an issue with my boundary conditions or something completely different??

I did try to change my upper and lower surfaces to a pressure farfiel but then I got divergence in the AMG Solver -> temperature...so I'm not sure if that is the correct thing to do. (in that case, I just turned off the energy equation until iteration 50 and then switched it on again, which resolved that problem but still didn't give me the correct answer, or anywhere near it)

I'd really appreciate any advice you that you may have at this, as I have been trying to solve this problem for a number of months now, and I have got no where, and as my thesis is due at the start of September, (and this is only one part of many), I am really up against it.

Thanks a lot.
Aidan