CFX mesh inflantation problem

zona · January 6, 2010, 17:39

Hi, I'm working on a pump flow analysis
I got some strange results so now I'm refining the mesh, any advice about the mesh elements sizes I think (I don't know if I'm right, that smaller inflantation is better but if I put inflantation 0.001 with the volume mesh I get warning big aspect ratio (default body spacing 0.005, default face spacing min 0.001 max 0.005) only if I put inflantation 0.005 I don't get the warning, but the inflantated region is quite big (or it seams to me it is

)
.
any advice on this subject, is there a big influence in the results depending on the inflantation (its a simple pump inlet - impeller - volute), by the way I/m using frosen rotor is this ok for calculations (I need q-h, q-power, and q - efficiency curves)

zona · January 8, 2010, 12:17

annyone ????

rikio · January 8, 2010, 23:17

Quote:

Originally Posted by zona

Hi, I'm working on a pump flow analysis
I got some strange results so now I'm refining the mesh, any advice about the mesh elements sizes I think (I don't know if I'm right, that smaller inflantation is better but if I put inflantation 0.001 with the volume mesh I get warning big aspect ratio (default body spacing 0.005, default face spacing min 0.001 max 0.005) only if I put inflantation 0.005 I don't get the warning, but the inflantated region is quite big (or it seams to me it is

)
.
any advice on this subject, is there a big influence in the results depending on the inflantation (its a simple pump inlet - impeller - volute), by the way I/m using frosen rotor is this ok for calculations (I need q-h, q-power, and q - efficiency curves)

What do you mean inflantation? I think you may encounter the big aspect ratio problem which means the mesh is stretched too much, small thickness with long length/width of the mesh. Decreasing the global mesh size or surface/line mesh size will get the aspect ratio lower down.
Wish it help.

sans · January 9, 2010, 02:02

Hi Your second mesh looks good, only problem is the big transition from the prism to the tets. Generally you would have convergence problems. I would increase the number of layers and the prism expansion ratio to get a better transition.
Frozen rotor does give good results for pumps but your final results does depend a lot on other factors also.

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January 8, 2010, 12:17		#2
zona New Member Zvonko Kostovski Join Date: Apr 2009 Location: Skopje, Macedonia Posts: 13 Rep Power: 17	annyone ????

January 9, 2010, 02:02		#4
sans Member SanS Join Date: Mar 2009 Posts: 41 Rep Power: 17	Hi Your second mesh looks good, only problem is the big transition from the prism to the tets. Generally you would have convergence problems. I would increase the number of layers and the prism expansion ratio to get a better transition. Frozen rotor does give good results for pumps but your final results does depend a lot on other factors also.