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Old   January 13, 2013, 06:47
Default Help with simulation of aerofoil
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Hi

I am doing a final year project looking at how the coefficient of lift and coefficient of drag vary with different NACA profiles. Prior to a couple of months ago had never used Ansys and am finding it pretty difficult. I can just about manage to run a simulation following the Cornell University tutorial.

What I would like to do is...

Run a full simulation (ie go through design modeler, meshing, fluent) with one aerofoil. Then when I have the data I need, go back into design modeler, change the coordinates file for the 3D curve, update all stages through workbench and then run the calculations again. However whenever I try this, the mesh generates differently (recently the mapped face meshing fails) and I cannot get a decent result.

Sorry to just come on here and ask for help but I have been trying this for weeks and to no avail.

Any help would be greatly appreciated.
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Old   January 25, 2013, 09:29
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Sárán Greene
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Hello,

I'm doing a similar sort of project using FLUENT. Could you possibly post some images of what exactly is wrong with the mesh? Is it simply unstructured? How many foils are in question here? In other words, how many foils are to be used throughout the project?

Just some side notes. Have you any comparative data available to verify that your simulation is, indeed, correct? Are you modelling compressible or incompressible flow? What turbulence model are you using to gather your results?
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Old   January 26, 2013, 11:50
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Thank you for your reply.

I thought of trying to explain my current problem but probably screen shots are the easiest way (a picture says a thousand words and all that).

Screen shot of design modeler... http://i47.tinypic.com/15s95ye.jpg

Zoomed in section at trailing edge... http://i46.tinypic.com/14x0ylg.jpg

Mesh ... http://i46.tinypic.com/313k9c7.jpg

Zoomed in mesh ... http://i50.tinypic.com/fjey9v.jpg

If anyone is interested, this is the NACA6610 profile, generated from 200 coordinate points.

As you can see the mesh is not properly arranged in the top right quadrant. I also notice that the Mapped Face Meshing has a kind of stop sign symbol next to it if that means anything? I believe part of the problem may be that the trailing edge crosses the line at x=1 although do not know how to transform the trailing edge into a sharp point.

Any help would be very appreciated. I have kind of been thrown into Ansys with no tuition and only a little help from my tutor.

In answer to your questions,
In total I am hoping to run simulations on approximately 50 aerofoils, yes I do have experimental data, I am unsure about compressible / incompressible flow and so far have been running laminar flow simulations, although if this is wrong then I am open to whatever anyone has to say.

Thank you for your help
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Old   January 27, 2013, 18:25
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I think the best thing to do, before you start into any more simulations, is to find out off of your supervisor whether or not the simulated flow is to be compressible or in-compressible. In terms of your mesh, I found this to be of some help to me when setting up my mesh. You can just refine it after. In terms of turbulence models choose either Spalart-Almaras or k-epsilon depending on your y+ values.

I'm unsure as to simply editing your Airfoil and then re-importing it into the solver with the new body. Anytime i've tried to do change geometry and import it, the FLUENT solver displays an error.

Having said all of this however, I'm in more or less the same position as yourself. I've had little to no training or help and my supervisor seems to ask questions for his benefit rather than mine. At least you have a full version of Ansys. I'm stuck with the educational one which limits the amount of nodes and faces etc.

I hope at least some of this has helped you.
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