[ICEM] Problem running mesh on fluent

luzikato · May 10, 2020, 04:38

Hello.

I'm learning how to generate a mesh with ICEM CFD. I'm using NACA 2412 as my geometry to study it's aerodynamics characteristics.

I followed some random meshing tutorial on youtube. However, when I ran it in fluent, I keep getting bad results with warnings such as :
1. Turbulent viscosity limited to viscosity ratio of 1.000000e+05 in xxx cells
2. Reversed flow in xxx face of outflow xx

I've done some browsing and this could be caused by bad mesh quality. But in ICEM, it shows quite good quality mesh. I also checked other quality parameters such as skewness and orthogonalities, but I don't really understand how it represents the mesh quality.

Is there any way I can improve my mesh quality in ICEM?

Thanks in advance,
Best Regards.

nacaMesh.jpg nacaMaxOrtho.JPG

nacaMinOrtho.JPG nacaSkew.JPG

Gert-Jan · May 10, 2020, 11:44

These messages have nothing to do with the mesh. Mesh is fine. Looks pretty good.

Reversed flow on the outlet means that the outlet is too close to the object. Just extend your geometry............

luzikato · May 10, 2020, 23:21

Thank you sir for the reply.

Actually, I have tried to expand the domain behind the airfoil to 30c but still get the reversed flow problem and also this turbulent viscosity ratio problem.

When I ran it in Fluent, the continuity and residuals were actually really good. Below 1e-5. However, the results (Cl, Cd, Cm) were bad.

I use BC as follows :
1. The top, bottom, and arc edge as inlet BC which I defined with viscosity intensity and hydraulic diameter and velocity of 11 m/s.
2. The straight vertical edge as outflow BC.

Am I missing something in defining the BCs?

Thanks,
Best regards.

Gert-Jan · May 11, 2020, 15:44

I don't know. I refuse to use Fluent. I always use CFX.
Therefore I would ask the Fluent forum.

May 10, 2020, 04:38	Problem running mesh on fluent	#1
luzikato New Member Anas Nur Fauzan Join Date: Oct 2019 Posts: 18 Rep Power: 6	Hello. I'm learning how to generate a mesh with ICEM CFD. I'm using NACA 2412 as my geometry to study it's aerodynamics characteristics. I followed some random meshing tutorial on youtube. However, when I ran it in fluent, I keep getting bad results with warnings such as : 1. Turbulent viscosity limited to viscosity ratio of 1.000000e+05 in xxx cells 2. Reversed flow in xxx face of outflow xx I've done some browsing and this could be caused by bad mesh quality. But in ICEM, it shows quite good quality mesh. I also checked other quality parameters such as skewness and orthogonalities, but I don't really understand how it represents the mesh quality. Is there any way I can improve my mesh quality in ICEM? Thanks in advance, Best Regards. nacaMesh.jpg nacaMaxOrtho.JPG nacaMinOrtho.JPG nacaSkew.JPG

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May 10, 2020, 11:44		#2
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,833 Rep Power: 27	These messages have nothing to do with the mesh. Mesh is fine. Looks pretty good. Reversed flow on the outlet means that the outlet is too close to the object. Just extend your geometry............

May 10, 2020, 23:21		#3
luzikato New Member Anas Nur Fauzan Join Date: Oct 2019 Posts: 18 Rep Power: 6	Thank you sir for the reply. Actually, I have tried to expand the domain behind the airfoil to 30c but still get the reversed flow problem and also this turbulent viscosity ratio problem. When I ran it in Fluent, the continuity and residuals were actually really good. Below 1e-5. However, the results (Cl, Cd, Cm) were bad. I use BC as follows : 1. The top, bottom, and arc edge as inlet BC which I defined with viscosity intensity and hydraulic diameter and velocity of 11 m/s. 2. The straight vertical edge as outflow BC. Am I missing something in defining the BCs? Thanks, Best regards.

May 11, 2020, 15:44		#4
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,833 Rep Power: 27	I don't know. I refuse to use Fluent. I always use CFX. Therefore I would ask the Fluent forum.