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Old   February 6, 2014, 13:08
Default Non reflective boundary condition
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ali
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I need to introduce non reflective boundary condition in CFX for a turbine cascade that I am modeling. Is there anyone who can help me with that?
I have searched a lot about this but I couldn't find anything useful.
I know that I can extend the domain to avoid imposing non reflective boundary condition but for some certain reason I cannot.
Any help would be much appreciated.
besides is there any mathematical description of this kind of boundary condition?

Thanks
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Old   February 6, 2014, 17:46
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Edmund Singer P.E.
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These are beta in CFX145. Turn on your beta features to get to this.
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Old   February 10, 2014, 15:05
Default beta feature
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Thanks Edmund for your reply,

What do you mean by beta features?
I am using CFX R15
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Old   February 10, 2014, 15:39
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I turned beta features on. But still I can not find non reflecting BC anywhere
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Old   February 24, 2014, 16:22
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Any help is much appreciated.
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Old   February 24, 2014, 17:34
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Boundary Condition: Opening : Tab Boudary Details : Mass And Momentum Acoustic Reflectivity (Beta) Chack the box
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Old   February 24, 2014, 18:32
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Thanks Edmund,

You mean I have to use opening instead of outlet?
When I change the boundary type to opening in the boundary detail tab there are five options available in the Mass and Momentum section:
1. opening pres and dirn
2. static pres and dirn
3. Entrainment
4. Cart. Vel. Components
5. Cyl. Vel. Components

I cannnot find Mass And Momentum Acoustic Reflectivity (Beta) anywhere.

Thanks
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Old   February 25, 2014, 06:00
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You need to select one of the five options which best reflect what's going on at the outlet. Beware: all five do vary by their definition quite significantly.

Once you've selected a type of opening, you can then click on the Mass and Momentum tab.
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Old   February 25, 2014, 12:13
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Thanks, but I do that but I cannot find the Mass And Momentum Acoustic Reflectivity (Beta) anywhere. There is no such tab. I am sure that I have turned on the Beta features of the CFX. I double checked it.
There is a mass and momentum section in the boundary detail tab from which I can only select the type of opening with no check box or anything. Apart from that I can not find any other mass and momentum tab. There are sources and plot options.
I am using CFX R15 by the way.
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Old   February 26, 2014, 12:49
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anyone? please?
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Old   February 26, 2014, 14:56
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I think you also have to enable a compressible gas using the Total Energy Model, and then under Case Options in CFX-Pre, "Enable Beta Features".
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Old   February 27, 2014, 12:37
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Edmund,

Thanks for the info. I switched to ideal gas so it is compressible now. Still no sign of that check box in the boundary detail opening tab. I also switched to total energy and there was also nothing. There is only a compressible production (with default value of 3.0) in "advanced turbulence control" section under turbulence section in fluid models tab.

In case you have done such thing before and if you still have that simulation files available, can you post the CCL here so that I can compare every detail with that just to see which part I am missing?

Thanks,
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Old   March 24, 2014, 18:55
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Edmund? Help?
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Old   March 25, 2014, 00:55
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It might not be in CFX-Pre yet so it might be a CCL only command. Have a look at the RULES file in the directory <CFX_ROOT>/etc and see if you can work out if CCL supports it and what the syntax is.
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Old   March 25, 2014, 08:55
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I dont know what to say. For me, it is in Pre under the tabs I listed.

Try contacting ANSYS support.
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Old   March 27, 2014, 09:21
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Ali, you should have Beta Options enabled, Ideal Gas and Total Energy Heat Transfer options in the domain. Then in Opening BC in Boundary Detail tab you'll have Acoustic Reflectivity option enabled. Or try editing BC in a Command Editor:
Quote:
DOMAIN: Default Domain
&replace BOUNDARY: sadfasdf
Boundary Type = OPENING
Interface Boundary = Off
Location = Hot
BOUNDARY CONDITIONS:
FLOW DIRECTION:
Option = Normal to Boundary Condition
END
FLOW REGIME:
Option = Subsonic
END
HEAT TRANSFER:
Opening Temperature = 20 [C]
Option = Opening Temperature
END
MASS AND MOMENTUM:
Option = Opening Pressure and Direction
Relative Pressure = 0 [Pa]
ACOUSTIC REFLECTIVITY:
Option = Reflective

END
END
TURBULENCE:
Option = Medium Intensity and Eddy Viscosity Ratio
END
END
END
END
But considering the name of the feature and the fact that OP needs non-reflective BC, I have doubts that's the things he's looking for.
Thanx a lot to Edmund Singer for info about this feature anyway.

PS CFX 14.5.1
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Old   March 28, 2014, 15:54
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Thanks Kristeen, will try that
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Old   April 10, 2014, 13:29
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Finally got it to work. Thanks guys
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