Negative torque

[kim.junyel]

Hello  everyone, 
I am getting a negative and positive torque in my Rotating Region Results. This was my graph for power in terms of torque and rpm.

While this was my convergence plot along with the model.

An explanation will be much appreciated. Thank you so much Autodesk CFD Forum. 

[frederic.gaillard.7]

Hello Kim, 

The torque value really dependant on the rotation of the impeller. Your graphic means that your archimede screw does not rotate continuously in the same direction. Based on the other image shared, your flow distribution reflex this torque oscillation. 

Fred

[kim.junyel]

Hello Sir @frederic.gaillard.7 , 
Is it safe to conclude that the values of negative and positive are equal?

[frederic.gaillard.7 · Accepted solution]

Hello Kim, 

If you sum your values in excell, it will give you the answers. Does the torque values make sense in term of your scenario design ? My guess would be  a smooth and steady torque as the solution progress in time instead of an oscillating behaviour. What do you thing ? 

Fred

[kim.junyel]

Good thing you're here! Now I got the idea! I was about to conclude the torque for the first variation and start doing the other variation but it seems that I need to fix my geometry again so the outlet of the turbine in will not be affected since my outlet water geometry has a tendency to come back once it reached its end. I think the solution is to extrude the outlet to bottom. After passing the turbine it will reduce the tendency to return back and settle in a pond like geometry of the outlet. Thank you so much, Sir Fred! You really are helping me in my project study. I have tons of problem solved by you haha.
-Kim