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Could temperature/density profile (of discrete data not a function) be used at inlet? 

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March 13, 2014, 03:16 
Could temperature/density profile (of discrete data not a function) be used at inlet?

#1 
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Quentin Hwang
Join Date: Oct 2012
Posts: 47
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Hey there,
Does it possible to use B.C. like discrete data in CFX? I modeled a thermal stratified reservoir in which temperature and density profiles are function of elevation, and now I would like to use dicrete points instead of the fitted curve in a similiar CFD model. How can I use it? Thanks a lot. 

March 13, 2014, 04:00 

#2 
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Peter
Join Date: Sep 2011
Location: Germany
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This can be done via Fortran and Junction Box routine. Read chapter 18.8 in the Modeling Guide for how to read in table data and create a profile boundary


March 13, 2014, 06:24 

#3 
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Quentin Hwang
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March 13, 2014, 06:43 

#4 
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Matthias Voß
Join Date: Mar 2009
Location: Berlin, Germany
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You can also read in datatables to a function and use this function for a b.c. in CFX Pre directly.
Also check "2.9. Profile Boundary Conditions" in CFX/the Modeling Guide 

March 13, 2014, 07:27 

#5  
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Quentin Hwang
Join Date: Oct 2012
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Quote:
Thank u very much. This is more useful for me as I do not know anything about Fortran. I am going in this way. Anyway, I will learn Fortran later. 

March 13, 2014, 08:47 

#6  
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Quentin Hwang
Join Date: Oct 2012
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Quote:
Could you tell that in detail please? I've learned 'Profile Boundary Conditions', and still do not know what to do. Here is my problem: at INLET B.C., I have temperature, density and pressure varying with elevation/depth, which is nothing to do with (x, y); the profile of INLET exported from cfdpost contains points (x, y, z, ...) which is not consistent with my experiment data (my profiles just vary with z). How can I cope with this issue? I am thinking about providing all the measured points by hand, but I do not know what to do with x and yposition. Thank you very much for your time. 

March 13, 2014, 09:40 

#7 
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Matthias Voß
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Location: Berlin, Germany
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When setting up the function you can copy/paste a large set of points into the schematic. So you need to provide density/temp/pressure wrt. z and use that function for all 3 components since x,y are independent you can feed in your func(z) and get a profile wrt. z.
Maybe you can provide a small setupcase or a pic. if i am getting you wrong. 

March 13, 2014, 10:05 

#8  
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Quentin Hwang
Join Date: Oct 2012
Posts: 47
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Quote:
So I am thinking if it is possible to use profile B.C.(making my own B.C. file) to provide the infomation. And I am confused with how to create the B.C. profile(including discrete data not a function) because I do not have lots of spatial points with which the CFX solver to interpolate. Thank u so much. 

March 13, 2014, 11:07 

#9 
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Matthias Voß
Join Date: Mar 2009
Location: Berlin, Germany
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i don´t get it...
assume you have a User Function called "test" with Option "Interpolation(Data Input)" with argument Units [m] and Result Units [C] and the following discrete data set Code:
0 10 5 15 10 10 15 5 20 20 and then you plot the expression (which is the same as using it as a bcprofile/initial value) you get a zigzag line. Between the points there will be a linear interpolation. If you want to get real steps you just add e.g. Code:
1e6 15 OR create a sufficient function f(x) with higher order terms (e.g 5 > ECXEL, MatLAB) from the given discrete data to smooth between your discrete data and use the mathematical function in the expression for the bc with z being your zcoordinate (test for division by 0 and clip between a min/max 1e8  1e15 just to be sure nothing goes out of bounds). 

March 13, 2014, 11:27 

#10  
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Quentin Hwang
Join Date: Oct 2012
Posts: 47
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Quote:
Thank you so much for your kindness. 

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