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Temperature dependent Stick-to-Wall

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Old   July 27, 2010, 04:50
Default Temperature dependent Stick-to-Wall
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Josef Runsten
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Hello,

We are simulating a turbine guide vane with ash particles present in the flow. We would like to know if there is a way to put a condition on the Stick-to-Wall Model, so that it will be used only if the temperature of the particle exceeds a certain value? A particle with lower temperature is supposed to bounce of the surface.

How do we write the code (if there is a way), specifying the temperature and wall behaviour? We are completely new to Fortran and CEL so any guidance would be greatly appreciated.
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Old   July 27, 2010, 07:26
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Not sure but hopefully you can do this using CEL and therefore not require fortran. It is just a matter of putting the coeff. of restitution as a function of particle temperature.
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Old   July 30, 2010, 05:13
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Thank you, but I'm still a bit lost.
Would this mean creating an expression close to

if( particle.Temperature>1000 [K], restitution coefficient==0, restitution coefficient==1)

?

I'm trying to find the answer in the CFX help, but haven't been able to. It says that the restititution coefficient is an available variable in CEL, but I can't see it anywhere.
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Old   July 30, 2010, 06:27
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or would it be as simple as to create an expression

MyExpression = if(particle.Temperature>1000[K], 1, 0)

and then writing MyExpression in the restitution dialog? I tried this but got the following error:

"The parameter "Parallel Coefficient od Restitution' in object .... is defined to be "Single valued" but it depends on the following field valued variables: , particle.Temperature".
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Old   July 30, 2010, 06:43
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Some variables can only be fixed values. I fear you have found one which can only be a fixed value. I would talk to your support office if there is away around this, otherwise you might need to do this in fortran.
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Old   August 2, 2010, 06:57
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CFX allows CEL for coefficient of restitution!
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Old   August 2, 2010, 07:12
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CCTech_Pune, please explain more if you know.
I tried if(particle.Temperature>1000[K], 1, 0), but that didn't work. Then I get the error message written in my previous post.
However, it works if I instead write something like ave(particle.Temperature)@BLADE or something like that, but that doesn't give us what we want I think? We want the temperature of each single particle, not an average (or max, min etc..).

Also, do you know if it's possible to do the same kind of thing in a transient run, using Stick-to-Wall? Stick-to-Wall forces all particles that hit the wall to become part of the wall film, but can this also be conditioned somehow? Not familiar with fortran so I don't really know how much we are allowed to modify.
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Old   August 2, 2010, 08:04
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Hi

I am checking for the same. I will update you.

Thanks
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