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November 29, 2012, 22:14 |
problem about cyclic boundary
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#1 |
Member
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 13 |
Hi foamers,
I am simulating a 2D channel flow. I used the pisoFoam solver for my case. After calculating for 5s, I have gotten an steady solution. Now I want to change the inlet and outlet boundary condition to periodic condition, which means I want to recycle the outflow back to the inflow. So I modified all the variables in the file of 5(t=5s)------the values of the internal field have not been changed, but for the inlet and outlet boundary I have changed them as cyclic type. However, after putting out several calculating results, I find the results are not what I have expected to. The velocities of the whole field just get more and more lower. Do I have a wrong modification? or something else Help me please. |
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November 30, 2012, 03:17 |
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#2 |
Senior Member
Lieven
Join Date: Dec 2011
Location: Leuven, Belgium
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Dear Sunxing,
The problem is that you don't impose a driving force in the latter case. Have a look at http://www.cfd-online.com/Forums/ope...onditions.html . If it is still not clear, feel free to ask again Regards, L |
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November 30, 2012, 09:05 |
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#3 | |
Member
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 13 |
Quote:
Hi Lieven, Thanks for your repley. I also have recognized that there maybe should have a differencial pressure between the inlet boundary and outlet boundary. I will look the link you offered and have a try tomorrow. thanks again. best, Sunxing |
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November 30, 2012, 21:24 |
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#4 | |
Member
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 13 |
Quote:
Hi L, Following your proposals in the link you offered, I have modified channelFoam to include RANS-models by comparing with pisoFoam. But I couldn't compile it successfully. Here are the files: Make/file my_channelFoam.C EXE = $(FOAM_USER_APPBIN)/my_channelFoam Make/options EXE_INC = \ -I$(LIB_SRC)/turbulenceModels/incompressible/turbulenceModel \ -I$(LIB_SRC)/turbulenceModels \ -I$(LIB_SRC)/turbulenceModels/incompressible/LES/LESModel \ -I$(LIB_SRC)/turbulenceModels/LES/LESdeltas/lnInclude \ -I$(LIB_SRC)/transportModels \ -I$(LIB_SRC)/transportModels/incompressible/singlePhaseTransportModel \ -I$(LIB_SRC)/finiteVolume/lnInclude \ -I$(LIB_SRC)/sampling/lnInclude EXE_LIBS = \ -lincompressibleLESModels \ -lincompressibleTurbulenceModel \ -lincompressibleRASModels \ -lincompressibleTransportModels \ -lfiniteVolume \ -lmeshTools |
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November 30, 2012, 21:25 |
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#5 | |
Member
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 13 |
Quote:
Hi L, Following your proposals in the link you offered, I have modified channelFoam to include RANS-models by comparing with pisoFoam. But I couldn't compile it successfully. Here are the files: Make/file my_channelFoam.C EXE = $(FOAM_USER_APPBIN)/my_channelFoam Make/options EXE_INC = \ -I$(LIB_SRC)/turbulenceModels/incompressible/turbulenceModel \ -I$(LIB_SRC)/turbulenceModels \ -I$(LIB_SRC)/turbulenceModels/incompressible/LES/LESModel \ -I$(LIB_SRC)/turbulenceModels/LES/LESdeltas/lnInclude \ -I$(LIB_SRC)/transportModels \ -I$(LIB_SRC)/transportModels/incompressible/singlePhaseTransportModel \ -I$(LIB_SRC)/finiteVolume/lnInclude \ -I$(LIB_SRC)/sampling/lnInclude EXE_LIBS = \ -lincompressibleLESModels \ -lincompressibleTurbulenceModel \ -lincompressibleRASModels \ -lincompressibleTransportModels \ -lfiniteVolume \ -lmeshTools Can you give me some more tips please? Thanks very much! Sunxing |
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December 1, 2012, 01:53 |
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#6 |
Senior Member
Lieven
Join Date: Dec 2011
Location: Leuven, Belgium
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Rep Power: 22 |
Hey Sunxing,
What is the error you get? At first sight, the option-file looks ok. Regards, L |
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December 1, 2012, 02:08 |
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#7 |
Member
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 13 |
Hi L,
Here is the error hint: my_channelFoam.C: in function ‘int main(int, char**)’: my_channelFoam.C:67:10: error: ‘turbulence’ has not yet been declared in this action scope /home/sun/OpenFOAM/OpenFOAM-2.1.1/src/finiteVolume/lnInclude/readPISOControls.H:3:15: warning: 未使用的变量‘nOuterCorr’ [-Wunused-variable] /home/sun/OpenFOAM/OpenFOAM-2.1.1/src/finiteVolume/lnInclude/readPISOControls.H:15:16: warning: 未使用的变量‘transonic’ [-Wunused-variable] make: *** [Make/linuxGccDPOpt/my_channelFoam.o] error 1 |
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December 1, 2012, 02:16 |
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#8 |
Member
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 13 |
Hi L,
Please pay attention to the my_channelfoam.c document posted in #4. There maybe something wrong in the document, but I don't know what it is. Regards, Sunxing |
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December 1, 2012, 10:58 |
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#9 |
Senior Member
Lieven
Join Date: Dec 2011
Location: Leuven, Belgium
Posts: 299
Rep Power: 22 |
In the file createFields.H, did you change
Code:
autoPtr<incompressible::LESModel> sgsModel ( incompressible::LESModel::New(U, phi, laminarTransport) ); Code:
autoPtr<incompressible::turbulenceModel> turbulence ( incompressible::turbulenceModel::New(U, phi, laminarTransport) ); L |
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December 2, 2012, 07:20 |
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#10 |
Member
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 13 |
Hi L,
Yes, you are right. I didn't change the code. And after changing the code, I have compiled it successfully. I will check the new solver by calculating my case. Thanks for your generous help. Best, Sunxing |
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December 2, 2012, 21:09 |
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#11 |
Member
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 13 |
Hey L,
I have simulated my channel case using the modified channelFoam solver. By using the modified solver, it did give me a result that with a cyclic boundary condition. But there is something wrong. For the velocity field, before I use the cyclic boundary condition, I just get a good result using the pisoFoam solver at the 5th second. Then I continued the simulation with the result at 5th second as a initial condition using the modified channelFoam. Here are the velocities at on slice: velocities of the 5th second using pisoFoam (3.21537 0 0) (3.79661 0 0) (4.13732 0 0) (4.4017 0 0) (4.62863 0 0) (4.83443 0 0) (5.02694 0 0) (5.21189 0 0) (5.39214 0 0) (5.56978 0 0) (5.74597 0 0) (5.92096 0 0) (6.09656 0 0) (6.27405 0 0) (6.45347 0 0) (6.63548 0 0) (6.82096 0 0) (7.00976 0 0) (7.20203 0 0) (7.39828 0 0) (7.5988 0 0) (7.80382 0 0) (8.01358 0 0) (8.22832 0 0) (8.44825 0 0) (8.67356 0 0) (8.90448 0 0) (9.14119 0 0) (9.3839 0 0) (9.6328 0 0) (9.88807 0 0) (10.1499 0 0) (10.4186 0 0) (10.6942 0 0) (10.9629 0 0) (11.2057 0 0) (11.4205 0 0) (11.6135 0 0) (11.789 0 0) (11.9501 0 0) (12.0991 0 0) (12.2379 0 0) (12.3678 0 0) (12.49 0 0) (12.6055 0 0) (12.7149 0 0) (12.8189 0 0) (12.9182 0 0) (13.013 0 0) (13.1039 0 0) (13.1911 0 0) (13.275 0 0) (13.3559 0 0) (13.4339 0 0) (13.5092 0 0) (13.5822 0 0) (13.6528 0 0) (13.7214 0 0) (13.7879 0 0) (13.8526 0 0) (13.9155 0 0) (13.9767 0 0) (14.0364 0 0) (14.0946 0 0) (14.1514 0 0) (14.2068 0 0) (14.261 0 0) (14.314 0 0) (14.3658 0 0) (14.4165 0 0) (14.4662 0 0) (14.5149 0 0) (14.5626 0 0) (14.6094 0 0) (14.6553 0 0) (14.7003 0 0) (14.7446 0 0) (14.788 0 0) (14.8308 0 0) (14.8727 0 0) (14.914 0 0) (14.9546 0 0) (14.9946 0 0) (15.0339 0 0) (15.0727 0 0) (15.1108 0 0) (15.1484 0 0) (15.1854 0 0) (15.2219 0 0) (15.2578 0 0) (15.2933 0 0) (15.3283 0 0) (15.3628 0 0) (15.3968 0 0) (15.4304 0 0) (15.4636 0 0) (15.4963 0 0) (15.5287 0 0) (15.5606 0 0) (15.5922 0 0) (15.5922 0 0) (15.5606 0 0) (15.5287 0 0) (15.4963 0 0) (15.4636 0 0) (15.4304 0 0) (15.3968 0 0) (15.3628 0 0) (15.3283 0 0) (15.2933 0 0) (15.2578 0 0) (15.2219 0 0) (15.1854 0 0) (15.1484 0 0) (15.1108 0 0) (15.0727 0 0) (15.0339 0 0) (14.9946 0 0) (14.9546 0 0) (14.914 0 0) (14.8727 0 0) (14.8308 0 0) (14.788 0 0) (14.7446 0 0) (14.7003 0 0) (14.6553 0 0) (14.6094 0 0) (14.5626 0 0) (14.5149 0 0) (14.4662 0 0) (14.4165 0 0) (14.3658 0 0) (14.314 0 0) (14.261 0 0) (14.2068 0 0) (14.1514 0 0) (14.0946 0 0) (14.0364 0 0) (13.9767 0 0) (13.9155 0 0) (13.8526 0 0) (13.7879 0 0) (13.7214 0 0) (13.6528 0 0) (13.5822 0 0) (13.5092 0 0) (13.4339 0 0) (13.3559 0 0) (13.275 0 0) (13.1911 0 0) (13.1039 0 0) (13.013 0 0) (12.9182 0 0) (12.8189 0 0) (12.7149 0 0) (12.6055 0 0) (12.49 0 0) (12.3678 0 0) (12.2379 0 0) (12.0991 0 0) (11.9501 0 0) (11.789 0 0) (11.6135 0 0) (11.4205 0 0) (11.2057 0 0) (10.9629 0 0) (10.6942 0 0) (10.4186 0 0) (10.1499 0 0) (9.88807 0 0) (9.6328 0 0) (9.3839 0 0) (9.14119 0 0) (8.90448 0 0) (8.67356 0 0) (8.44825 0 0) (8.22832 0 0) (8.01358 0 0) (7.80382 0 0) (7.5988 0 0) (7.39828 0 0) (7.20203 0 0) (7.00976 0 0) (6.82096 0 0) (6.63548 0 0) (6.45347 0 0) (6.27405 0 0) (6.09656 0 0) (5.92096 0 0) (5.74597 0 0) (5.56978 0 0) (5.39214 0 0) (5.21189 0 0) (5.02694 0 0) (4.83443 0 0) (4.62863 0 0) (4.4017 0 0) (4.13732 0 0) (3.79661 0 0) (3.21537 0 0) ) velocities from the result simulated by modified channelFoam (0.0121199 6.54506e-14 -1.24588e-24) (0.0387828 2.96048e-13 0) (0.070777 1.27878e-12 0) (0.109168 2.99316e-12 0) (0.155235 6.11546e-12 0) (0.210512 1.12437e-11 0) (0.276839 1.93505e-11 0) (0.356423 3.18278e-11 0) (0.451912 5.06432e-11 0) (0.566479 7.85707e-11 0) (0.703928 1.19505e-10 0) (0.868816 1.78873e-10 0) (1.06659 2.64189e-10 0) (1.30374 3.85748e-10 0) (1.58797 5.57427e-10 0) (1.92825 7.97381e-10 0) (2.33465 1.12826e-09 0) (2.81703 1.57755e-09 0) (3.3801 2.18251e-09 0) (4.01052 3.00405e-09 0) (4.66714 4.1331e-09 0) (5.30211 5.69131e-09 0) (5.88836 7.81885e-09 0) (6.41863 1.06324e-08 0) (6.89597 1.42212e-08 0) (7.32797 1.86395e-08 0) (7.72352 2.39051e-08 0) (8.09103 3.00086e-08 0) (8.43765 3.69018e-08 0) (8.76912 4.45051e-08 0) (9.08994 5.27133e-08 0) (9.40359 6.13977e-08 0) (9.71272 7.0381e-08 0) (10.0194 7.94176e-08 0) (10.309 8.79927e-08 0) (10.5648 9.57437e-08 0) (10.7876 1.02631e-07 0) (10.9854 1.08794e-07 0) (11.1635 1.1439e-07 0) (11.3255 1.19552e-07 0) (11.4743 1.24368e-07 0) (11.6119 1.28851e-07 0) (11.74 1.33067e-07 0) (11.8598 1.37033e-07 0) (11.9724 1.40776e-07 0) (12.0786 1.44319e-07 0) (12.1791 1.47685e-07 0) (12.2745 1.50891e-07 0) (12.3653 1.53948e-07 0) (12.4519 1.56866e-07 0) (12.5346 1.5965e-07 0) (12.6137 1.62301e-07 0) (12.6896 1.64818e-07 0) (12.7624 1.672e-07 0) (12.8324 1.69443e-07 0) (12.8997 1.71539e-07 0) (12.9645 1.73486e-07 0) (13.027 1.75286e-07 0) (13.0871 1.76917e-07 0) (13.1452 1.78352e-07 0) (13.2012 1.7959e-07 0) (13.2553 1.80641e-07 0) (13.3075 1.81478e-07 0) (13.3579 1.82075e-07 0) (13.4065 1.82418e-07 0) (13.4535 1.82478e-07 0) (13.4988 1.82229e-07 0) (13.5425 1.81651e-07 0) (13.5846 1.80736e-07 0) (13.6252 1.79481e-07 0) (13.6643 1.77889e-07 0) (13.7019 1.75947e-07 0) (13.7381 1.73643e-07 0) (13.7728 1.70967e-07 0) (13.8061 1.67913e-07 0) (13.838 1.64479e-07 0) (13.8684 1.60664e-07 0) (13.8975 1.56476e-07 0) (13.9252 1.51937e-07 0) (13.9516 1.47004e-07 0) (13.9766 1.41741e-07 0) (14.0002 1.3617e-07 0) (14.0224 1.30305e-07 0) (14.0434 1.24164e-07 0) (14.063 1.17764e-07 0) (14.0813 1.11128e-07 0) (14.0983 1.04277e-07 0) (14.114 9.72324e-08 0) (14.1284 9.00131e-08 0) (14.1416 8.26374e-08 0) (14.1535 7.51215e-08 0) (14.1641 6.74939e-08 0) (14.1735 5.97678e-08 0) (14.1818 5.19607e-08 0) (14.1888 4.40897e-08 0) (14.1946 3.61849e-08 0) (14.1992 2.81969e-08 0) (14.2027 2.02247e-08 0) (14.205 1.2223e-08 0) (14.2062 4.19454e-09 0) (14.2062 -3.78626e-09 0) (14.205 -1.17996e-08 0) (14.2027 -1.97858e-08 0) (14.1992 -2.77476e-08 0) (14.1946 -3.56773e-08 0) (14.1888 -4.3565e-08 0) (14.1818 -5.13996e-08 0) (14.1735 -5.91682e-08 0) (14.1641 -6.6855e-08 0) (14.1535 -7.44454e-08 0) (14.1416 -8.19257e-08 0) (14.1284 -8.92701e-08 0) (14.114 -9.64633e-08 0) (14.0983 -1.03488e-07 0) (14.0813 -1.10325e-07 0) (14.063 -1.16954e-07 0) (14.0434 -1.23354e-07 0) (14.0224 -1.29502e-07 0) (14.0002 -1.3538e-07 0) (13.9766 -1.40969e-07 0) (13.9516 -1.46255e-07 0) (13.9252 -1.51217e-07 0) (13.8975 -1.55789e-07 0) (13.8684 -1.60011e-07 0) (13.838 -1.63863e-07 0) (13.8061 -1.67336e-07 0) (13.7728 -1.70429e-07 0) (13.7381 -1.73144e-07 0) (13.7019 -1.75488e-07 0) (13.6643 -1.77468e-07 0) (13.6252 -1.79096e-07 0) (13.5846 -1.80386e-07 0) (13.5425 -1.81335e-07 0) (13.4988 -1.81946e-07 0) (13.4535 -1.82227e-07 0) (13.4065 -1.82196e-07 0) (13.3579 -1.81879e-07 0) (13.3075 -1.81305e-07 0) (13.2553 -1.8049e-07 0) (13.2012 -1.7946e-07 0) (13.1452 -1.7824e-07 0) (13.0871 -1.76823e-07 0) (13.027 -1.75213e-07 0) (12.9645 -1.73425e-07 0) (12.8997 -1.71493e-07 0) (12.8324 -1.6941e-07 0) (12.7624 -1.67181e-07 0) (12.6896 -1.64811e-07 0) (12.6137 -1.62305e-07 0) (12.5346 -1.59665e-07 0) (12.4519 -1.56892e-07 0) (12.3653 -1.53983e-07 0) (12.2745 -1.50934e-07 0) (12.1791 -1.47736e-07 0) (12.0786 -1.44377e-07 0) (11.9724 -1.40839e-07 0) (11.8598 -1.37102e-07 0) (11.74 -1.33141e-07 0) (11.6119 -1.28929e-07 0) (11.4743 -1.24449e-07 0) (11.3255 -1.19635e-07 0) (11.1635 -1.14474e-07 0) (10.9854 -1.08878e-07 0) (10.7876 -1.02713e-07 0) (10.5648 -9.58222e-08 0) (10.309 -8.80663e-08 0) (10.0194 -7.9483e-08 0) (9.71272 -7.04349e-08 0) (9.40359 -6.14401e-08 0) (9.08994 -5.27443e-08 0) (8.76912 -4.45252e-08 0) (8.43765 -3.69125e-08 0) (8.09103 -3.00115e-08 0) (7.72352 -2.39021e-08 0) (7.32797 -1.86326e-08 0) (6.89597 -1.4212e-08 0) (6.41863 -1.06226e-08 0) (5.88836 -7.80965e-09 0) (5.30211 -5.68348e-09 0) (4.66714 -4.12679e-09 0) (4.01052 -2.99948e-09 0) (3.3801 -2.17945e-09 0) (2.81703 -1.57561e-09 0) (2.33465 -1.12706e-09 0) (1.92825 -7.96643e-10 0) (1.58797 -5.56977e-10 0) (1.30374 -3.85472e-10 0) (1.06659 -2.64019e-10 0) (0.868816 -1.78767e-10 0) (0.703928 -1.19439e-10 0) (0.566479 -7.85314e-11 0) (0.451912 -5.06207e-11 0) (0.356423 -3.18162e-11 0) (0.276839 -1.93446e-11 0) (0.210512 -1.1239e-11 0) (0.155235 -6.11725e-12 0) (0.109168 -3.00226e-12 0) (0.070777 -1.24716e-12 0) (0.0387828 -3.4431e-13 0) (0.0121199 -3.42311e-14 0) Apparently the velocity filed has something wrong. So I wander that what leads to the result. I think that maybe these are the reasons: (1) I did not modify the channelFoam correctly. (2) I did not give good initial condition for the case (3) The property constants I offered are not accurate. However I can't make sure what is the real reason. So please help me. |
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December 2, 2012, 21:15 |
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#12 |
Member
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 13 |
Hey L,
Maybe I should give you the files of my case, but the size of my case is too be to be uploaded. So may I have your email address for further communication. Regards, Sunxing |
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December 2, 2012, 21:17 |
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#13 |
Member
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 13 |
Hey L,
Maybe I should give you the files of my case, but the size of my case is too be to be uploaded. So may I have your email address for further communication. Regards, Sunxing |
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December 3, 2012, 03:01 |
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#14 |
Senior Member
Lieven
Join Date: Dec 2011
Location: Leuven, Belgium
Posts: 299
Rep Power: 22 |
Hey Sunxing,
There are a few things you should check: Is the channelFoam simulation fully converged? Is the Ubar set correctly in constant/transportProperties? Do the pressure gradients match? Regards, L |
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December 3, 2012, 04:01 |
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#15 |
Member
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 13 |
Hey L
I have checked the three points you mentioned. Firstly, the channelFoam simulation is fully converged. Secondly I give the correct averaged velocity----Ubar. Lastly, I can't make sure weather the pressure gradient match, for I just have taken the p file from the result at 5th second simulated by pisoFoam as the initial p file for modified channelFoam solver and changed the type of inlet/outlet to cyclic without any change in the internalField. Regards, Sunxing |
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December 3, 2012, 04:44 |
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#16 | |
Senior Member
Lieven
Join Date: Dec 2011
Location: Leuven, Belgium
Posts: 299
Rep Power: 22 |
Quote:
Btw are you using the same wall treatment for both? It's just that especially near the walls the difference is profiles is very big. How did you calculate the velocity profiles on the slice? Is this done in Openfoam (e.g. with postchannel) or with paraView? Can you compare the results with analytic profiles? Flow between two parallel plates is for the laminar case known as a poiseuille flow. If necessary you can lower the reynolds number if the flow is not laminar. This way you can check your wall treatment cause zeroGradient for nut is not really appropriate... Regards, L |
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December 3, 2012, 05:54 |
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#17 |
Member
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 13 |
Hi L,
Given your suggestions, I have modified my case: 1) In the p file, I set it uniform filed equal to zero. 2) Yes, I am using the same wall treatment for both. 3) As for the velocity, I have the experimental data as initial inlet data and it obeys the 1/7 power law i.e. u=u_max*(y/H)^(1/7), where u_max is the velocity at middle of the walls, y is the distance normal to the wall, H is the half height between two walls. So I just calculated out Ubar by the formula----Ubar=2*u_max/((1+1/7)*(2+1/7)). 4) in my case the nu is 1.5486e-05, so the Reynolds number is not big. Did I make these changes correctly? Regard, Sunxing |
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