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How to model laminar flow in 2d pipe flow with Comsol

Posted Jun 22, 2015, 8:17 a.m. EDT Fluid & Heat, Computational Fluid Dynamics (CFD), Mesh, Modeling Tools & Definitions, Parameters, Variables, & Functions, Results & Visualization, Studies & Solvers 4 Replies

Pavan Patel
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Hi,
I want to simulate a standard laminar flow problem using comsol. This problem is being for validating Comsol. The 2D pipe geometry is 0.2 m dia and 8 m length. The flow is laminar flow. Velocity is 1 m/s.
The density of the pipe is 1 kg/m^3 and viscosity mu is 0.002. So, Re = 100 < 2300.

The maximum velocity for parabolic profile shall be 2x1=2 m/s but after solving the velocity is coming 1.49 m/s. In what way the modelling shall be performed so that the desired results can be simulated in a stard format not as hit and trial method.

I have taken one side of width as inlet and other side as outlet. The other two longitudinal dimensions are taken as wall with no slip condition. Poutlet = 0 and 101325 Pa for two different cases.

Kindly help me modelling this problem.

Thanks.
4 Replies Last Post Jun 24, 2015, 6:14 a.m. EDT
Jeff Hiller COMSOL Employee

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Posted: 9 years ago Jun 22, 2015, 8:42 a.m. EDT
Hello Pavan,
You may want to post your mph file otherwise it's hard for other users to make suggestions as to what you may have done wrong.
Jeff
Hello Pavan, You may want to post your mph file otherwise it's hard for other users to make suggestions as to what you may have done wrong. Jeff
Lasse Murtomäki
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Posted: 9 years ago Jun 22, 2015, 9:05 a.m. EDT
There is an analytical solution that tells that the vmax = 1.5 m/s, nothing wrong with Comsol:

v(x) = 150*x*(0.2 - x)

v_aveg = 1 m/s = v_init
There is an analytical solution that tells that the vmax = 1.5 m/s, nothing wrong with Comsol: v(x) = 150*x*(0.2 - x) v_aveg = 1 m/s = v_init
Pavan Patel
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Posted: 9 years ago Jun 24, 2015, 6:10 a.m. EDT
Hi Mr.Jeff
Thanks for your reply. I think I have figured out that why the results were not matching. I was trying to model a pipe flow with 2-D problem as explained in the main details. I modeled a 3-D pipe and the results shows that Vmax = 2Vavg where as for 2-D Vmax=1.5Vag.

I modeled 2-D problem selecting 2-D axisymmetric and then the Vmax=2Vavg. It seems that Comsol was treating the previous 2-D problem as channel flow and giving Vmax=1.49 m/s (Vavg=1 m/s).

Kindly comment on my observations.

Thanks and Regards
Pavan Kr Patel
Hi Mr.Jeff Thanks for your reply. I think I have figured out that why the results were not matching. I was trying to model a pipe flow with 2-D problem as explained in the main details. I modeled a 3-D pipe and the results shows that Vmax = 2Vavg where as for 2-D Vmax=1.5Vag. I modeled 2-D problem selecting 2-D axisymmetric and then the Vmax=2Vavg. It seems that Comsol was treating the previous 2-D problem as channel flow and giving Vmax=1.49 m/s (Vavg=1 m/s). Kindly comment on my observations. Thanks and Regards Pavan Kr Patel
Pavan Patel
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Posted: 9 years ago Jun 24, 2015, 6:14 a.m. EDT
Hi Mr. Lasse Murtomäki
Thanks for your reply. I think I have figured out that why the results were not matching. I was trying to model a pipe flow with 2-D problem as explained in the main details. I modeled a 3-D pipe and the results shows that Vmax = 2Vavg where as for 2-D Vmax=1.5Vag.

I modeled 2-D problem selecting 2-D axisymmetric and then the Vmax=2Vavg. It seems that Comsol was treating the previous 2-D problem as channel flow and giving Vmax=1.49 m/s (Vavg=1 m/s).

Kindly comment on my observations.

Thanks and Regards
Pavan Kr Patel
Hi Mr. Lasse Murtomäki Thanks for your reply. I think I have figured out that why the results were not matching. I was trying to model a pipe flow with 2-D problem as explained in the main details. I modeled a 3-D pipe and the results shows that Vmax = 2Vavg where as for 2-D Vmax=1.5Vag. I modeled 2-D problem selecting 2-D axisymmetric and then the Vmax=2Vavg. It seems that Comsol was treating the previous 2-D problem as channel flow and giving Vmax=1.49 m/s (Vavg=1 m/s). Kindly comment on my observations. Thanks and Regards Pavan Kr Patel

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