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May 18, 2020, 08:37 
udf boundary condition (vorticity)

#1 
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yassine
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Hi
I don't know how to write udf boundary condition for vorticity .I bring to your attention that my work has been done on the nanofluid and more precisely I am working on the configuration of Rayleigh Bénard (natural convection). Fig. 1 shows a schematic diagram of the RayleighBénard (RB) problem. For the RB problem, the distance between the upper cold and lower hot plates is defined by H and the width of the top and bottom plates is defined by W. The plates’ width W is considered infinite and treated by a periodicity boundary condition. The bottom plate is maintained at a hot temperature TH=50 C whereas the top plate is maintained at a cold temperature TC=22 C. The fluid enclosed between the plates is water based nanofluid containing CuO nanoparticles. The nanofluid is assumed incompressible and the flow is assumed as laminar and twodimensional. thanks Inkedgh_LI.jpg 

May 18, 2020, 09:08 
boundary using UDF vorticity

#2 
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yassine
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Can anyone tell me how to apply dv/dx=0 and omega=du/dy at a boundary using UDF.
[v=delta(psi)/delta(x) u=delta(psi)/delta(y)] Inkedgh_LI.jpg 

May 18, 2020, 09:15 
Wall boundary

#3 
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Fluent uses momentum conservation and not vorticity or Poisson's equation. The equation you have is written in terms of streamfunction and implies noslip condition. That is the default condition in Fluent and you don't need to do anything
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May 18, 2020, 09:52 

#4 
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yassine
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But I fond in the results that dv/dx is not equal 0


May 18, 2020, 09:55 
Gradient

#5 
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That won't be 0 and should not be. Look at the document you shared. The condition is NOT
but , implying velocity is 0.
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May 18, 2020, 10:05 

#6 
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yassine
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May 18, 2020, 10:15 
Noslip

#7 
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That's correct and noslip implies velocity is 0 at the wall, i.e., the default condition in Fluent. As far as rotation is concerned, in a 2D case, rotation is possible only around zaxis, so, where is a function of velocity gradient.
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May 18, 2020, 10:21 

#8  
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yassine
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Quote:
okay thank you so much 

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