Moment and Torque

TheMightySpartan · September 27, 2018, 10:08

Hello,

I m running simulation of a turbine in the transient state.

When I run and get moment on my blades about centre in FLUENT I am able to produce the moment vs flow time graph to get the average moment.

When I go to CFD post and use torque_y()@blades, I get a different value for a corresponding timestep.

I have done some reading and I think it is due to the moment only considering pressure forces and the torque force being the pressure and viscous forces.

Can I get a plot of Torque vs Flowtime anywhere in FLUENT or CFD Post instead of individually getting it from each timestep?

Thanks

Gert-Jan · September 28, 2018, 03:39

1) Can't you define a monitor in Fluent that provides you the torque as a function of time? In that case, I would ask this in the fluent forum. Probably someone has tried this before.
2) In Post you can calculate the torque in an alternative way:
abs(sum(Velocity in Stn Frame u * Force X + Velocity in Stn Frame v * Force Y + Velocity in Stn Frame w * Force Z)@Calc Wall Region). Maybe you can setup such an alternative calculation in Fluent and monitor this?

3) Why not perform this calculation in CFX. It is much better equiped for rotating equipment than Fluent. You can easily setup a monitor that provide the torque during the calculation. (I would never do this in Fluent.)

September 27, 2018, 10:08	Moment and Torque	#1
TheMightySpartan New Member Join Date: Oct 2017 Posts: 25 Rep Power: 8	Hello, I m running simulation of a turbine in the transient state. When I run and get moment on my blades about centre in FLUENT I am able to produce the moment vs flow time graph to get the average moment. When I go to CFD post and use torque_y()@blades, I get a different value for a corresponding timestep. I have done some reading and I think it is due to the moment only considering pressure forces and the torque force being the pressure and viscous forces. Can I get a plot of Torque vs Flowtime anywhere in FLUENT or CFD Post instead of individually getting it from each timestep? Thanks

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September 28, 2018, 03:39		#2
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,827 Rep Power: 27	1) Can't you define a monitor in Fluent that provides you the torque as a function of time? In that case, I would ask this in the fluent forum. Probably someone has tried this before. 2) In Post you can calculate the torque in an alternative way: abs(sum(Velocity in Stn Frame u * Force X + Velocity in Stn Frame v * Force Y + Velocity in Stn Frame w * Force Z)@Calc Wall Region). Maybe you can setup such an alternative calculation in Fluent and monitor this? 3) Why not perform this calculation in CFX. It is much better equiped for rotating equipment than Fluent. You can easily setup a monitor that provide the torque during the calculation. (I would never do this in Fluent.)