CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > OpenFOAM

problem about cyclic boundary

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   November 29, 2012, 23:14
Default problem about cyclic boundary
  #1
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
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.
Attached Images
File Type: jpg nut.jpg (24.6 KB, 24 views)
Sunxing is offline   Reply With Quote

Old   November 30, 2012, 04:17
Default
  #2
Senior Member
 
Lieven
Join Date: Dec 2011
Location: Mol, Belgium
Posts: 295
Rep Power: 13
Lieven will become famous soon enough
Dear Sunxing,

The problem is that you don't impose a driving force in the latter case.

Have a look at ribbed channel / simpleFoam / boundary conditions . If it is still not clear, feel free to ask again

Regards,


L
Lieven is offline   Reply With Quote

Old   November 30, 2012, 10:05
Default
  #3
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
Quote:
Originally Posted by Lieven View Post
Dear Sunxing,

The problem is that you don't impose a driving force in the latter case.

Have a look at ribbed channel / simpleFoam / boundary conditions . If it is still not clear, feel free to ask again

Regards,


L


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
Sunxing is offline   Reply With Quote

Old   November 30, 2012, 22:24
Default
  #4
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
Quote:
Originally Posted by Lieven View Post
Dear Sunxing,

The problem is that you don't impose a driving force in the latter case.

Have a look at ribbed channel / simpleFoam / boundary conditions . If it is still not clear, feel free to ask again

Regards,


L

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
Attached Files
File Type: c my_channelFoam.C (4.7 KB, 7 views)
Sunxing is offline   Reply With Quote

Old   November 30, 2012, 22:25
Default
  #5
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
Quote:
Originally Posted by Lieven View Post
Dear Sunxing,

The problem is that you don't impose a driving force in the latter case.

Have a look at ribbed channel / simpleFoam / boundary conditions . If it is still not clear, feel free to ask again

Regards,


L

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
Sunxing is offline   Reply With Quote

Old   December 1, 2012, 02:53
Default
  #6
Senior Member
 
Lieven
Join Date: Dec 2011
Location: Mol, Belgium
Posts: 295
Rep Power: 13
Lieven will become famous soon enough
Hey Sunxing,

What is the error you get? At first sight, the option-file looks ok.

Regards,


L
Lieven is offline   Reply With Quote

Old   December 1, 2012, 03:08
Default
  #7
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
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
Sunxing is offline   Reply With Quote

Old   December 1, 2012, 03:16
Default
  #8
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
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
Sunxing is offline   Reply With Quote

Old   December 1, 2012, 11:58
Default
  #9
Senior Member
 
Lieven
Join Date: Dec 2011
Location: Mol, Belgium
Posts: 295
Rep Power: 13
Lieven will become famous soon enough
In the file createFields.H, did you change

Code:
    autoPtr<incompressible::LESModel> sgsModel
    (
        incompressible::LESModel::New(U, phi, laminarTransport)
    );
to

Code:
    autoPtr<incompressible::turbulenceModel> turbulence
    (
        incompressible::turbulenceModel::New(U, phi, laminarTransport)
    );
Cheers,


L
Lieven is offline   Reply With Quote

Old   December 2, 2012, 08:20
Default
  #10
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
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
Sunxing is offline   Reply With Quote

Old   December 2, 2012, 22:09
Default
  #11
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
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.
Sunxing is offline   Reply With Quote

Old   December 2, 2012, 22:15
Default
  #12
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
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
Sunxing is offline   Reply With Quote

Old   December 2, 2012, 22:17
Default
  #13
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
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
Sunxing is offline   Reply With Quote

Old   December 3, 2012, 04:01
Default
  #14
Senior Member
 
Lieven
Join Date: Dec 2011
Location: Mol, Belgium
Posts: 295
Rep Power: 13
Lieven will become famous soon enough
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
Lieven is offline   Reply With Quote

Old   December 3, 2012, 05:01
Default
  #15
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
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
Sunxing is offline   Reply With Quote

Old   December 3, 2012, 05:44
Default
  #16
Senior Member
 
Lieven
Join Date: Dec 2011
Location: Mol, Belgium
Posts: 295
Rep Power: 13
Lieven will become famous soon enough
Quote:
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
This is something you don't need to do (although it won't make a difference after converging). The pressure field in the channel calculated with channelFoam will not be the same as the pressure field from pisoFoam i.e. the pisoFoam solution will contain the pressure gradient explicitly in the solution while this won't be the case for channelFoam. Therefore, the channelFoam pressure solution should be a uniform field equal to zero for a flow in a pipe/between plates without any obstructions.

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
Lieven is offline   Reply With Quote

Old   December 3, 2012, 06:54
Default
  #17
Member
 
sqing
Join Date: Sep 2012
Location: Dalian
Posts: 77
Rep Power: 4
Sunxing is on a distinguished road
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
Sunxing is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Wind turbine simulation Saturn CFX 34 October 16, 2014 05:27
Radiation interface hinca CFX 15 January 26, 2014 18:11
Cyclic boundary matching - help needed Robert_B STAR-CD 5 June 15, 2011 08:03
Domain Imbalance HMR CFX 3 March 6, 2011 21:10
problem with boundary condition??? smn CFX 5 November 24, 2009 07:37


All times are GMT -4. The time now is 07:48.