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[swak4Foam] Problem with fully developed velocity profile groovyBC in 2D axi-sym mesh |
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July 17, 2014, 00:37 |
Problem with fully developed velocity profile groovyBC in 2D axi-sym mesh
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#1 |
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Harshad Lalit
Join Date: May 2013
Posts: 26
Rep Power: 13 |
Hello All,
I am studying a premixed jet flame using reactingFoam in a 2D axisymmetric mesh and using a groovyBC to simulate fully developed turbulent flow through the premixed inlet. The geometry has a wall beside the premixed inlet (at x=0.0075m). I am using the following code to set up my velocity profile: Code:
Inlet { type groovyBC; value uniform (0 0 0); variables ( "n=7;" //power law coefficient n "R=0.0075;" //pipe radius "Umean=7.5;" //calculate mean velocity "Umax=13.2;" //calculate max velocity "profile=Umax*pow(1-sqrt(pow(pos().x,2)+pow(pos().z,2))/R,(1/n));" //calcucate power law velocity profile Umax*(1-r/R)^(1/n) ); valueExpression "normal()*-profile"; //apply to boundary, normal() is surface normal vector and minus is needed for inflow } Code:
x y z u(m/s) v(m/s) w(m/s) 0 0 0 0 13.097 0 0.00105 0 0 1.8e-2 12.9125 -7.34282e-06 0.0021 0 0 0.000278988 12.5902 -8.95149e-06 0.003 0 0 -0.00146174 12.2672 -2.48713e-07 0.00375 0 0 -0.00351349 11.9474 -2.31918e-05 0.0039 0 0 -0.00399891 11.8788 -9.06154e-06 0.0042 0 0 -0.00526191 11.7293 -3.19546e-05 0.0045 0 0 -0.00667307 11.5738 -1.0456e-06 0.0051 0 0 -0.0111364 11.2036 -3.2705e-05 0.00555 0 0 -0.0147763 10.8722 5.90284e-06 0.0057 0 0 -0.0148122 10.7366 2.19331e-05 0.006 0 0 -0.0149064 10.4634 -4.21239e-07 0.00645 0 0 -0.0167839 9.89666 -2.98323e-06 0.0066 0 0 0.00138561 9.61408 0.000813393 0.00675 0 0 0.0273102 9.29285 0.00173083 0.0069 0 0 0.0532349 8.97162 0.0006639 0.00705 0 0 0.0728419 8.32117 0.000127202 0.0072 0 0 0.0820423 7.12842 0.000463938 0.00735 0 0 0.0912427 5.93567 0.000299331 0.0075 0 0 0.0918162 4.74207 -0.0003617 |
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July 22, 2014, 17:07 |
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#2 | |
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
Posts: 4,225
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Quote:
To check which values groovyBC sets I usually a) have a look at the written field file b) open the case in paraview. Deselect internalField, select the patch in question and inspect it in PV
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July 24, 2014, 01:19 |
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#3 |
New Member
Harshad Lalit
Join Date: May 2013
Posts: 26
Rep Power: 13 |
Hello Bernhard. Thanks for your reply . I am sampling using the "uniform" technique in the sample utility, however I have deleted a couple of columns of my data to keep it short.
I was wondering if my problem has something to do with the mesh. My axisymmetric domain has the axis in the vertical - Y direction , whereas most of the problems I have seen have their axis in the horizontal X direction. Will my mesh be still consistent with the OpenFoam format? Please let me know. Thanks! |
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July 24, 2014, 06:58 |
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#4 | ||
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Bernhard Gschaider
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Quote:
Quote:
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July 24, 2014, 12:02 |
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#5 |
New Member
Harshad Lalit
Join Date: May 2013
Posts: 26
Rep Power: 13 |
Hi Bernhard,
So instead of having a groovyBC i just put in a fixedValue bc (0.0 13.0 0.0) for my inlet. The domain next to the inlet is a wall (0.0 0.0 0.0). I used the "midpoint" sampling technique with 'cell' interpolation and the following in the output I got for velocity at inlet after 0.01 seconds. Code:
distance, Ux, Uy, Uz 0.000124881, -0.000182222, 13.0002, 6.40391e-14 0.000374643, -0.000366104, 13.0002, 1.46322e-13 0.000624405,-0.000569023, 13.0001, 2.17518e-13 0.000874167, -0.000749703, 13, 1.79184e-13 0.00112393, -0.000908129, 12.9999, 1.23171e-13 0.00137369, -0.00105632, 12.9999, 1.11654e-13 0.00162345, -0.00120575, 12.9998, 1.72996e-13 0.00187322, -0.00136315, 12.9998, 3.27864e-13 0.00212298, -0.00153432, 12.9998, 5.30865e-13 0.00237274, -0.00172296, 12.9998, 4.06978e-13 0.0026225, -0.00193339, 12.9997, 3.88529e-13 0.00287226, -0.00217462, 12.9997, 4.72995e-13 0.00312203, -0.00245306, 12.9997, 2.78539e-13 0.00337179, -0.00277999, 12.9997, 1.41409e-13 0.00362155, -0.00318224, 12.9997, 6.0643e-14 0.00387131, -0.00367517, 12.9997, 6.17558e-15 0.00412107, -0.00431001, 12.9998, -4.18723e-14 0.00437084, -0.00515109, 12.9998, -8.86959e-14 0.0046206, -0.00625099, 12.9999, -1.175e-13 0.00487036, -0.00772528, 12.9999, -8.92134e-14 0.00512012, -0.00974374, 13, -5.14688e-14 0.00536988, -0.012564, 13.0001, -2.47128e-14 0.00561965, -0.0165905, 13.0004, -9.6174e-15 0.00586941, -0.0225386, 13.0008, -1.10196e-15 0.00611917, -0.0317697, 13.002, 4.90887e-15 0.00636893, -0.0458528, 13.0047, 8.50871e-15 0.00661869, -0.0621625, 13.0074, 7.54421e-15 0.00686846,-0.0489905, 12.9861, 3.24075e-14 0.00711822, -0.202212, 12.8795, 8.25841e-14 0.00736798, 0.487566, 12.1117, 2.76338e-14 I have attached an image of the closeup of mesh (the highlighted part is my inlet) |
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July 24, 2014, 13:30 |
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#6 | |
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
Posts: 4,225
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Quote:
The sample utility is good for looking at cell values. If I want the face values on a patch I usually have a look at the field-file or check it in ParaView
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July 24, 2014, 13:50 |
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#7 |
New Member
Harshad Lalit
Join Date: May 2013
Posts: 26
Rep Power: 13 |
But shouldnt atleast the Ux be 0 because my velocity is only in the y-direction?
The Ux seems to be pretty signicant and not close to zero unlike the Uz. |
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July 24, 2014, 14:28 |
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#8 |
Assistant Moderator
Bernhard Gschaider
Join Date: Mar 2009
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Well: the wall is slowing the fluid down but the BC pushes from the back. To preserve conservation it has to go somewhere. In your case: left
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