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August 24, 2009, 10:53 |
flow distribution index (gamma function)
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#1 |
Member
TonyD
Join Date: Apr 2009
Posts: 85
Rep Power: 17 |
Hi all,
in fluent you could write a piece of usercode that represented the flow distribution index (gamma) gamma = 1-V_prime/2*Vavg Vprime=Area AVGD of abs(V-Vavg) Has anyone done something similar in StarCCM+ and willing to explain me? Last edited by bramv101; August 27, 2009 at 09:16. |
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August 24, 2009, 17:01 |
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#2 |
Senior Member
Join Date: Mar 2009
Location: Austin, TX
Posts: 160
Rep Power: 18 |
You can do it by creating a new report and a field function...
1. Add an "Area Averaged Report" and add the boundary or section plane you are interested in to the report. Set velocity magnitude as the scalar. This will create another new field function that will have the value of the the average velocity. The name of the new field function will be based on the name you gave your report. 2. You can then create a new field function called gamma: 1 - abs($VelocityMagnitude - $VelocityAverageReport) / (2 * $VelocityAverageReport) (The name of the field function "$VelocityAverageReport" will depend on what you named your report) Note that you will have to create an average velocity report and a different gamma field function for each boundary or section that you want to work with. |
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August 26, 2009, 10:53 |
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#3 |
Member
TonyD
Join Date: Apr 2009
Posts: 85
Rep Power: 17 |
Many Thx this worked for me
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August 27, 2009, 04:48 |
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#4 |
Member
TonyD
Join Date: Apr 2009
Posts: 85
Rep Power: 17 |
If i created the field function, how can i then display this value?
Another avg report doesnt seam logical to me |
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August 27, 2009, 09:16 |
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#5 |
Member
TonyD
Join Date: Apr 2009
Posts: 85
Rep Power: 17 |
Never mind, i should use expression report.
However one thing: your definition of the gamma function is somewhat odd to me. you do not use axial velocity but magnitude instead, and you dont area avg your abs(V_cell_axial-AA_v_axial) |
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August 27, 2009, 15:51 |
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#6 |
Senior Member
Join Date: Mar 2009
Location: Austin, TX
Posts: 160
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If you want to use axial velocity you need to create a new field function to use instead of velocity magnitude:
abs(dot(unit($$Area), $$Velocity)) |
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April 20, 2015, 08:30 |
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#7 | |
New Member
Priyank Vijapur
Join Date: Jan 2014
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Quote:
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April 20, 2015, 11:17 |
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#8 |
Senior Member
Join Date: Mar 2009
Location: Austin, TX
Posts: 160
Rep Power: 18 |
The formula I posted (six years ago!) is area averaged. It's up to you to determine whether you need area or mass averaged. I don't know your requirements.
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April 21, 2015, 05:08 |
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#9 |
Senior Member
Gajendra Gulgulia
Join Date: Apr 2013
Location: Munich
Posts: 144
Rep Power: 13 |
Hi
Mass averaged reports are generally needed when you are considering the bulk volume of your continua or a part of it, or in more layman terms the control volume for eg: total pressure, static pressure, total temperature, entropy, enthalpy etc. However the surface averaged reports (as the name suggests) gives the values at a surface, for eg uniformity index and other values which you may need at surface. (I am omitting the mathematics, you can always look them up in the help manual ) |
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April 21, 2015, 07:43 |
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#10 |
New Member
Priyank Vijapur
Join Date: Jan 2014
Posts: 2
Rep Power: 0 |
Thank you for your prompt response! Well i'm running flow analysis for an SCR. Acceptance criteria for FDI is 0.85, When i calculated it considering Area avg it was 0.84, when i considered Mass avg i got 0.86. So was wondering if i can show mass avg results :P Thanks, Priyank V
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