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spanwise averaging for LES backward facing step

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Old   July 21, 2008, 12:06
Default spanwise averaging for LES backward facing step
  #1
Sungho Yoon
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I completed my LES calculation for a backward facing step and I'm processing the data.

I want to average the data in the spanwise direction but don't know how to do it.

Can anyone let me know how to do it?

Sungho
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Old   July 22, 2008, 09:37
Default Re: spanwise averaging for LES backward facing ste
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Rogerio Fernandes Brito
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I´m not sure, but you can make this on CFX-Pre, "Output Control", "Trn Stats" tab, for a transient simulation. In "Transient Statistics 1", choose "Arithmetic Average". In "Output Variables List", choose "Velocity".

Do u wanna calculate the recirculation point´in the average time? I did it and my result is about 6.
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Old   July 23, 2008, 03:16
Default Re: spanwise averaging for LES backward facing ste
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Sungho Yoon
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Thank you. I will try it. My recirculation point is about 7 based on mid span data. (experimental data indicates 6 as you predicted) I may need to refine the grid.

By the way, do you think it is better to average in spanwise direction rather than just process the data at mid span? Le, Moin and Kim(1997) averaged in spanwise direction in their DNS calculation.
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Old   July 23, 2008, 06:05
Default Re: spanwise averaging for LES backward facing ste
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Sungho Yoon
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I thoguth about it and realised that it is averaging in time rather than spanwise averaging.

Thanks anyway.
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Old   July 23, 2008, 07:54
Default Re: spanwise averaging for LES backward facing ste
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Rogerio Fernandes Brito
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So, my results were about 7.2, using a FORTRAN code in 2D dimension. I used the finite element method, using triangle elements, Galerking scheme with LES and structure function sub-grid scale model. I did an average in time for each x location. You said: "...to average in spanwise direction rather than just process the data at mid span...", I didn´t understand you, sorry, my english is bad. What does "spanwise" mean?
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Old   July 23, 2008, 09:39
Default Re: spanwise averaging for LES backward facing ste
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Sungho Yoon
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I did a three-dimensional calculation with u(y) inlet profile.

To explain in more detail, my backward facing step is generated in (x,y) coordinate but it was extended in z (spanwise) direction with periodic condition in both z boundaries.

I wanted to average in z direction to get a data similar to two-dimensional calculation.

Since I don't know how to do the spanwise average in a simple way, I currently process data at mid z plane only.

Regards, Sungho
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Old   July 23, 2008, 10:34
Default Re: spanwise averaging for LES backward facing ste
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Rogerio Fernandes Brito
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I understood now your problem! u have to average the componentes of your velocities in 3 directions, by the projection of the area of the element in each plane. The researches in Federal University of Uberlandia (www.ufu.br), in Brazil, probably did this type of simulation. Look for Professor Dr. Ellie Padilla or Professor Dr. Aristeu da Silveira Neto.
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