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Change density; reynolds number

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Old   April 4, 2012, 10:31
Default Change density; reynolds number
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Thierry Chavagnan
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Hi everyone!!!!

Im doing my dissertation on a modified Clark Y wing. I only just started usiing ANSYS and I would like to know how can I change the density of the air or reynolds number.

I would like to simulate an aircraft flying at 5000m.

Thank you for your consideration
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Old   April 4, 2012, 17:55
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Glenn Horrocks
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CFX is a dimensional solver. This means you have to give it input values in a consistent set of units - usually SI, so metres, seconds, Kelvin, kg. You cannot give it inputs in non-dimensional numbers like Reynolds number. So you simply convert your Reynolds number to a set of dimensional values, that is a density, velocity and viscosity. If you are modelling a airfoil in air then use air properties and work out the velocity from there.

Changing the density is trivial - have a look at the tutorials for how to set material properties.
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Old   April 5, 2012, 04:39
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Thierry Chavagnan
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Thank you so much for replying.

I managed to change the density but Im not sure whether to use ideal gas or real gas. I want to simulate the wing flying at an altitude of 3000m. I was thinking that if I use ideal gas, this might use less computingting power and less time.

Will there any big difference in the results between using ideal or real gas??? I read that real gas should be use on for supersonic speed but my experiment is being done at low subsonic.

What are your thought please???

Thank you
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Old   April 5, 2012, 16:17
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Mohammed
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No point in treating it as a real gas.
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Old   April 5, 2012, 17:04
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Thierry Chavagnan
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Cheers guys...!!! Thank you so much for your help.

I have one last question, does anyone know how I can get lift & drag coefficient produced by my wing from the results obtained in CFX-post????

The only results that I have got were: velocity, pressure, eddy viscosity and some others.... Bearing in mind that my simulation was in 3D

Thanks again guys, your help is much appreciated and your name is definitely going to be in my acknowledgement with your permission of course.
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