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-   -   Volume Fraction, profile data problem (http://www.cfd-online.com/Forums/cfx/67534-volume-fraction-profile-data-problem.html)

 cfxmar August 18, 2009 07:34

Volume Fraction, profile data problem

Hi,
I´m simulating waves using profile data at the inlet. As I have experimental data from the height of the wave vs time, I used a profile data containing x,y,z and volume fraction as columnes.
The results aren´t correct.

x and y are fixed values (the point where the height of the wave is measured). I have put x as the time and y = 0 all time.
z is the mesured height.
Volume Fraction values are 1 or 0 depending on the value of z (positive or negative)
The expression: Filename.Volume Fraction((t*1[s^-1]*1[m]),y,z)
It doesn´t work!!!
Would kindly anyone tell me what could be wrong?
Thank you very much in advance

Cfxmar

 ghorrocks August 18, 2009 18:25

I think a 1D interpolation function would be more appropriate than the 3D one you are using. Try that.

Glenn Horrocks

 cfxmar August 19, 2009 04:39

Thank you, Glenn.
I have tried that but as the problem is 3D, the profile data needs three columns for x,y,z and one for the volume fraction. CFX doesn´t let me load the profile data file with only 2 columns (one for x as the time and one for the volune fraction)

 Lance August 19, 2009 04:47

I just did the same thing, but for a measured mass flow rate instead and a 1D profile data function worked fine for me.

Looks like:
FUNCTION: MassFlowInlet
Argument Units = [m]
Extend Max = true
Extend Min = true
File Name = massflow.csv
Option = Profile Data
Spatial Fields = X
DATA FIELD: Mass Flow Rate
Field Name = Mass Flow Rate
Result Units = [kg s^-1]
END
END

and the boundary condition:
BOUNDARY: inlet
Boundary Type = INLET
Location = F18.16
BOUNDARY CONDITIONS:
FLOW DIRECTION:
Option = Normal to Boundary Condition
END
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Mass Flow Rate = MassFlowInlet.Mass Flow Rate(FT)
Option = Mass Flow Rate
END
TURBULENCE:
Option = Low Intensity and Eddy Viscosity Ratio
END
END
END

where FT is defined as FT = 1[m/s]*t

Lance

 cfxmar August 19, 2009 05:45

Thank you very much, Glenn and Lance.
I´m running the simulation, tomorrow I will see the results.

Cfxmar

 ghorrocks August 19, 2009 08:09

Quote:
 I have tried that but as the problem is 3D, the profile data needs three columns for x,y,z and one for the volume fraction. CFX doesn´t let me load the profile data file with only 2 columns (one for x as the time and one for the volune fraction)
Come on, think outside the square.... You don't need a whole variable field to store the volume fraction. It can be stored as a single number (that is the height of the surface at that time) and the volume fraction field can be evaluated for height from that using a simple CEL step or if function. Now you can use a 1D interpolation function.

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