Fluent calculating cylindrical coordinates

Falldox · January 21, 2017, 06:06

Hi,

I'm currently simulating a stirred tank using the MRF method. My system revolves around the y-axis and I also set that in fluent (origin 0,0,0 with rotation axis 0,1,0). This seems to work fine, when I go to CFD post and analyze my results, the flow field looks fine. Within CFD post, you can define an axis of rotation again, to calculate the cylindrical coordinates and corresponding velocities (vz, vr, vtheta) and they all make sense. However, in the data file I export from Fluent, the coordinates of my cells and the velocities make no sense in the cylindrical coordinate system, only in carthesian. I found out Fluent calculates these coordinates based on an axis of rotation set to z. Does anybody know how to change the way (change axis) how Fluent calculates these cylindrical quantities?

As an addition: oddly enough, when I just rotate my geometry 90 degrees to align the rotation axis with z, my convergence is significantly worse (I can barely reach scaled residuals of 10^-5 for NS and 10^-4 for continuity. This is something I will definitely look into myself, but it would be very helpful if someone can help me with the first question.

Thank you

FluentStarter · January 31, 2017, 10:10

"Cell Zone Conditions" ->Edit and the change of rotation axis does not resolve your problem?

January 21, 2017, 06:06	Fluent calculating cylindrical coordinates	#1
Falldox New Member Robert Join Date: Jan 2017 Posts: 4 Rep Power: 9	Hi, I'm currently simulating a stirred tank using the MRF method. My system revolves around the y-axis and I also set that in fluent (origin 0,0,0 with rotation axis 0,1,0). This seems to work fine, when I go to CFD post and analyze my results, the flow field looks fine. Within CFD post, you can define an axis of rotation again, to calculate the cylindrical coordinates and corresponding velocities (vz, vr, vtheta) and they all make sense. However, in the data file I export from Fluent, the coordinates of my cells and the velocities make no sense in the cylindrical coordinate system, only in carthesian. I found out Fluent calculates these coordinates based on an axis of rotation set to z. Does anybody know how to change the way (change axis) how Fluent calculates these cylindrical quantities? As an addition: oddly enough, when I just rotate my geometry 90 degrees to align the rotation axis with z, my convergence is significantly worse (I can barely reach scaled residuals of 10^-5 for NS and 10^-4 for continuity. This is something I will definitely look into myself, but it would be very helpful if someone can help me with the first question. Thank you

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January 31, 2017, 10:10		#2
FluentStarter Member Join Date: Apr 2014 Location: N/A Posts: 47 Rep Power: 12	"Cell Zone Conditions" ->Edit and the change of rotation axis does not resolve your problem?