Issue with Coordinate Systems and U Velocity on CFD-Post

CiaranStubbsParker · August 3, 2020, 07:02

Hi there,

I have been conducting a simulation regarding airflow past cooling towers. I have been using a square-shaped flow domain, with the flow passing diagonally across, passing the cooling tower. The results have been fine, except for measuring velocity U.

As this uses the global coordinate system for measuring, all answers are skewed. Shown in the first image is the coordinate system the solver is using regarding velocity U, along with the direction of the flow. The second image shows the desired coordinate system. I have been able to make the desirable coordinate system in CFD-Post using a 'coordinate frame,' but I have been unable to make the velocity U calculate using it as a reference.

Is it possible to change the coordinate system the velocity U uses in CFD-Post? If not, how do I change the global coordinate system in Fluent / Design Modeler / ANSYS Meshing?

Thanks for your time.

Kind regards,
Ciaran.

- Current coordinate system

- Desired coordinate system

evcelica · August 11, 2020, 16:39

Just do a coordinate transformation.
Use sine and cosine of the angle to calculate velocity in your coordinate frame.

satyamshk2 · July 18, 2022, 13:50

You can insert a Coordinate frame and calculate values with respect to that. Go to insert - Coordinate frame -

August 3, 2020, 07:02	Issue with Coordinate Systems and U Velocity on CFD-Post	#1
CiaranStubbsParker New Member Ciaran Parker Join Date: Jun 2020 Posts: 2 Rep Power: 0	Hi there, I have been conducting a simulation regarding airflow past cooling towers. I have been using a square-shaped flow domain, with the flow passing diagonally across, passing the cooling tower. The results have been fine, except for measuring velocity U. As this uses the global coordinate system for measuring, all answers are skewed. Shown in the first image is the coordinate system the solver is using regarding velocity U, along with the direction of the flow. The second image shows the desired coordinate system. I have been able to make the desirable coordinate system in CFD-Post using a 'coordinate frame,' but I have been unable to make the velocity U calculate using it as a reference. Is it possible to change the coordinate system the velocity U uses in CFD-Post? If not, how do I change the global coordinate system in Fluent / Design Modeler / ANSYS Meshing? Thanks for your time. Kind regards, Ciaran. - Current coordinate system - Desired coordinate system

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August 11, 2020, 16:39		#2
evcelica Senior Member Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,188 Rep Power: 23	Just do a coordinate transformation. Use sine and cosine of the angle to calculate velocity in your coordinate frame.

July 18, 2022, 13:50		#3
satyamshk2 New Member CFD Join Date: May 2022 Posts: 15 Rep Power: 4	You can insert a Coordinate frame and calculate values with respect to that. Go to insert - Coordinate frame -