Calculated torque value not matching with fluent value

Jahaan · December 6, 2020, 07:53

Hi everyone

I am a student, recently gained intrest in CFD and started working on small cases to learn and understand tool and physics.

I have been working on a simple case of "transient simulation, Flow over a rotating circle -2D". I am using pressure inlet and outlet as boundry conditions, with constant RPM. My challenge is i am not able to match calculated torque value and fluent torque value. Also I have observed that torque value is changing with time even tough with constant RPM

Need help to figure out my case. Thanks in advance

pakk · December 6, 2020, 19:42

If you want help, you have to share some more details.

At minimum:
-which pressures and flow rate did you use?
-what is the torque value calculated by you?
-how did you calculate that?
-what is the torque value calculated by fluent?

Jahaan · December 10, 2020, 11:03

Hi Pakk,

Thanks for your reply, my apologies for not giving complete information.

I have used simple model of (R)0.07m circle in a rectangular domain, Circle rotating with 1780.23 rad/sec. I have used KOmega solver with boundry condition (Pressure inlet and pressure outlet) in transient case and ran for 4 sec, ANSYS torque value is 19Nm.

I have theoretically calculated torque value by (Moment of inertia of circle (I) X Angular acceleration (Alpha)) and the derived value is 0.008Nm.

I am not able to understand where i am going wrong.

Thanks for asking me :-)

December 6, 2020, 07:53	Calculated torque value not matching with fluent value	#1
Jahaan New Member Jahaan Join Date: Dec 2020 Posts: 4 Rep Power: 5	Hi everyone I am a student, recently gained intrest in CFD and started working on small cases to learn and understand tool and physics. I have been working on a simple case of "transient simulation, Flow over a rotating circle -2D". I am using pressure inlet and outlet as boundry conditions, with constant RPM. My challenge is i am not able to match calculated torque value and fluent torque value. Also I have observed that torque value is changing with time even tough with constant RPM Need help to figure out my case. Thanks in advance

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December 6, 2020, 19:42		#2
pakk Senior Member Join Date: Nov 2013 Posts: 1,965 Rep Power: 26	If you want help, you have to share some more details. At minimum: -which pressures and flow rate did you use? -what is the torque value calculated by you? -how did you calculate that? -what is the torque value calculated by fluent?

December 10, 2020, 11:03		#3
Jahaan New Member Jahaan Join Date: Dec 2020 Posts: 4 Rep Power: 5	Hi Pakk, Thanks for your reply, my apologies for not giving complete information. I have used simple model of (R)0.07m circle in a rectangular domain, Circle rotating with 1780.23 rad/sec. I have used KOmega solver with boundry condition (Pressure inlet and pressure outlet) in transient case and ran for 4 sec, ANSYS torque value is 19Nm. I have theoretically calculated torque value by (Moment of inertia of circle (I) X Angular acceleration (Alpha)) and the derived value is 0.008Nm. I am not able to understand where i am going wrong. Thanks for asking me :-)