# DNS of square duct at Re_tau = 600

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 November 19, 2012, 16:57 #21 Senior Member   Filippo Maria Denaro Join Date: Jul 2010 Posts: 1,651 Rep Power: 23 - what about your dy+ and dz+ close to walls? - the plot of the static pressure is for the periodic part?

 November 19, 2012, 17:13 #22 Senior Member     Paolo Lampitella Join Date: Mar 2009 Location: Italy Posts: 534 Blog Entries: 14 Rep Power: 17 Sorry, forget about L, i don't know where did it come from... i meant AR=W/H. The viscosity is what i called mu. The periodicity has to be set via Text User Interface (yes, between inlet and outlet): gr -> mo -> mp Once it is set, you can define your pressure gradient in the relative panel (the dp/dx i defined above) Once you set everything and start by the perturbed RANS solution, an initial development time is required, over which the solution will adapt (slowly, because of the periodicity) to the computational setup. You can see that by monitoring the volume average (over the full domain) of the velocity magnitude squared. Once this quantity starts oscillating around some mean value you are done, you can start collecting the statistics.

November 19, 2012, 18:20
#23
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Sijal Ahmed Memon (turboenginner@gmail.com)
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Quote:
 Originally Posted by FMDenaro - what about your dy+ and dz+ close to walls? - the plot of the static pressure is for the periodic part?
dy+ and dz+ are similar to Y+? or there is any difference?

Yes this is the plot of static pressure for the periodic part.

November 19, 2012, 18:38
#24
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Filippo Maria Denaro
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Quote:
 Originally Posted by Far dy+ and dz+ are similar to Y+? or there is any difference? Yes this is the plot of static pressure for the periodic part.

y+ is the local position in the direction normal to wall, expressed in wall units, that is y+= u_tau*y/ni = Re_tau* y/h. Not that h is characteristic length used in Re_tau.

dy+ and dz+ are the mesh sizes expressed in wall units. Close to the walls you need 3 -4 cells within y+ and z+ =1.

The plot of the pressure seems to me not to fulfill the periodic condition in streamwise direction

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