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CFX-PRE monitor point... multi-variable arguments for locator based functions |
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November 17, 2011, 08:37 |
CFX-PRE monitor point... multi-variable arguments for locator based functions
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#1 |
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Join Date: Mar 2011
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Is it somehow possible to do as the title of the thread reads, and define a multi-variable argument, locator based function?
A little more info: My simulation involves a jet of fluid, pointing in the X positive direction. Using CFX_PRE V13 I want to find the spread angle of the jet, i.e angle between the majority of the vectors and the vector (1,0,0) (x-positive direction) So I start with the equation for an angle between 2 vectors: where u is the vector (1,0,0) and v is the velocity vector at the mesh locator OUTLET. since the u vector is fully dercribed in only one direction and is the unity vector, the formula can be simplified to: *Note; here alpha is actually defining the half spread angle. This could be set as an expression as follows: alpha=acos(Velocity u*1 [m s^-1]/(Velocity u^2+Velocity v^2+Velocity w^2)) *Note I multiply with 1 [m s^-1] to keep dimensions consistent. Now if I set a monitor point as: massFlowAve(alpha)@OUTLET I get a error message along the lines of: "The function 'massFlowAve' referenced in parameter 'Expression Value' in object '/FLOW:Flow Analysis 1/OUTPUT CONTROL/MONITOR OBJECTS/MONITOR POINT:ALPHA_MONITOR' has an invalid argument, 'alpha'. Only arguments that consist of a single recognised variable name are supported by the solver." As far as I can tell, the problem above basically means that I can only define one variable (e.g Velocity u) and not 2 or 3 variables in the locator based function; massFlowAve(). Note that the exact same method DOES work for me in CFX-POST. Thas is defining the same expression, and using the function calculator. So does anyone have an idea how to circumvent this problem in CFX-PRE?? Thanks in advance! |
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November 17, 2011, 15:52 |
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#2 |
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There's an easy way to do this... create an algebraic Additional Variable equal to alpha and then use the AV as the argument to the locator based function.
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November 17, 2011, 16:22 |
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#3 |
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You're right! works perfect. Thanks for the help.
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November 17, 2011, 23:16 |
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#4 |
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DB
Join Date: Apr 2011
Posts: 87
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Hi,
I tried to do the same, but I am not getting how to define algebric additional variable. I was able to define AV but the problem is I am not getting an option of writing an expression for it or giveing its type as algebric, i searched CFX help but to no avail.
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-D.B |
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November 18, 2011, 10:42 |
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#5 |
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After you create the AV, you need to edit your domain to enable the AV in that domain. It's in the domain settings that you say it's algebraic.
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November 19, 2011, 00:15 |
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#6 |
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DB
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Thanks,
Now I am getting it.
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February 8, 2015, 20:51 |
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#7 |
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Diego Jaimes
Join Date: Feb 2015
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Hi, I really tried to do the same that you posted. I am trying to set a boundary condition in a multi-phase simulation dependent of (Fluid1. Volume Fraction*Velocity v)=VC= my AV, but when I tried to define the boundary condition I got this messaje
"The Additional Variable 'VC' referenced in parameter 'Normal Speed' in object '/FLOW:Flow Analysis 1/DOMAINefault Domain/BOUNDARY:top/BOUNDARY CONDITIONS/MASS AND MOMENTUM' is fluid-dependent and therefore requires a fluid prefix." How can I set a prefix on my AV? Thank you for your help Last edited by jaimesdiegop; February 9, 2015 at 11:18. |
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March 19, 2021, 01:25 |
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#8 | |
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YangLu
Join Date: Sep 2020
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Quote:
Thnaks. |
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March 19, 2021, 05:41 |
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#9 |
Senior Member
Gert-Jan
Join Date: Oct 2012
Location: Europe
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In 2015, Diego wanted to evaluate Fluid1.Volume Fraction*Velocity v
I guess this has to be: Fluid1.Volume Fraction*Fluid1.Velocity v In other words, the variable Velocity v that is evaluated needs to be linked to a defined material, which is Fluid1 in this particular case. |
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