Too fine mesh, is that a Problem?

AS_allways · September 7, 2015, 07:38

If I have a too fine mesh in my Domain for turbulent flow. Is there a physical Problem besides increasing the calculation time?

Is it possible, that the mesh, being too fine, is going to Show unphysical results?

thanks very much

Bruno Machado · September 7, 2015, 10:23

I do not think it can cause any "unphysical" problem. What can happen is if it is too fine the round-off error can be significant and cause divergence problem, but I think it is unlikely to happen.

If you think your results do not show what is expected, you might need to check your inputs.

AS_allways · September 7, 2015, 16:28

thanks for your answer.
for acoustic calculations I am reading the static pres over the time at one point and analyse ist afterwards with the fft tool inside FLuent.

at low velocities ~ 25m/s, a pressure inlet is not working (flow direction is reversed somehow). Is it neccessary to have high velocities for pressure inlet?

Taking air as ideal gas, fluent allways ask me to check my boundary conditions suggesting to take a pressure inlet.

Has anyone an idea how to deal with this?

CeesH · September 8, 2015, 06:48

Can you elaborate in what way your mesh is 'too fine'?

September 7, 2015, 07:38	Too fine mesh, is that a Problem?	#1
AS_allways New Member Abdalla Join Date: Oct 2013 Posts: 7 Rep Power: 12	If I have a too fine mesh in my Domain for turbulent flow. Is there a physical Problem besides increasing the calculation time? Is it possible, that the mesh, being too fine, is going to Show unphysical results? thanks very much

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September 7, 2015, 10:23		#2
Bruno Machado Senior Member Bruno Machado Join Date: May 2014 Posts: 271 Rep Power: 12	I do not think it can cause any "unphysical" problem. What can happen is if it is too fine the round-off error can be significant and cause divergence problem, but I think it is unlikely to happen. If you think your results do not show what is expected, you might need to check your inputs.

September 7, 2015, 16:28		#3
AS_allways New Member Abdalla Join Date: Oct 2013 Posts: 7 Rep Power: 12	thanks for your answer. for acoustic calculations I am reading the static pres over the time at one point and analyse ist afterwards with the fft tool inside FLuent. at low velocities ~ 25m/s, a pressure inlet is not working (flow direction is reversed somehow). Is it neccessary to have high velocities for pressure inlet? Taking air as ideal gas, fluent allways ask me to check my boundary conditions suggesting to take a pressure inlet. Has anyone an idea how to deal with this?

September 8, 2015, 06:48		#4
CeesH Senior Member Cees Haringa Join Date: May 2013 Location: Delft Posts: 607 Rep Power: 0	Can you elaborate in what way your mesh is 'too fine'?