[Other] Mesh Refinment

fatemehfarshi62 · June 22, 2016, 01:59

Hi every one!

I have a turbulent flow for a channel. But for a first approximation I modeled it in laminar condition. the results had an approximate error about 30-35%. Can I perform the mesh study on the laminar case or It has to be in turbulent case? Thanks for help.

Zbynek · June 22, 2016, 08:38

The mesh-independent study is not limited to turbulent flows, although it needs to be said that the mesh refinement (as well as transition from the lower-order schemes to the higher-order schemes) has a very significant effect especially on the turbulent quantities. That's at least my personal experience.

An important thing is what the focus of your simulation is. If it is, for example, the boundary layer resolution, then mesh refinement is desirable near the walls, no matter whether the flow is turbulent or laminar (although I should probably say that the laminar flow does not have a real boundary layer - in this case, I refer rather to a region with a large velocity gradient).

You are saying that the error is about 30%. Error of what? Besides you said that the flow is turbulent but you modeled the channel as laminar so I wonder how you could compare anything (experiments vs computations)?

fatemehfarshi62 · June 22, 2016, 10:08

Hi! problem solved thank you. The point is in smooth channels velocity profiles are more or less similar to turbulent case.

June 22, 2016, 01:59	Mesh Refinment	#1
fatemehfarshi62 Member Fatemeh Join Date: Dec 2015 Location: Isfahan,Iran Posts: 39 Rep Power: 10	Hi every one! I have a turbulent flow for a channel. But for a first approximation I modeled it in laminar condition. the results had an approximate error about 30-35%. Can I perform the mesh study on the laminar case or It has to be in turbulent case? Thanks for help.

June 22, 2016, 08:38		#2
Zbynek Member Join Date: Jun 2016 Posts: 66 Rep Power: 10	The mesh-independent study is not limited to turbulent flows, although it needs to be said that the mesh refinement (as well as transition from the lower-order schemes to the higher-order schemes) has a very significant effect especially on the turbulent quantities. That's at least my personal experience. An important thing is what the focus of your simulation is. If it is, for example, the boundary layer resolution, then mesh refinement is desirable near the walls, no matter whether the flow is turbulent or laminar (although I should probably say that the laminar flow does not have a real boundary layer - in this case, I refer rather to a region with a large velocity gradient). You are saying that the error is about 30%. Error of what? Besides you said that the flow is turbulent but you modeled the channel as laminar so I wonder how you could compare anything (experiments vs computations)? Last edited by Zbynek; June 23, 2016 at 03:41.

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June 22, 2016, 10:08		#3
fatemehfarshi62 Member Fatemeh Join Date: Dec 2015 Location: Isfahan,Iran Posts: 39 Rep Power: 10	Hi! problem solved thank you. The point is in smooth channels velocity profiles are more or less similar to turbulent case.