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defining angular velocity of an external gear pump

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Old   June 19, 2020, 09:53
Default defining angular velocity of an external gear pump
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Hello,

I've recently tried to simulate an external gear pump ( with two gears) and used a "DEFINE_CG_MOTION" code for defining the angular velocity of the gears. I solved all the code errors and I could see the rotation of the gears in the dynamic mesh preview. But, when I change the rotation speed to see its effect on the inlet mass flow rate ( any changes in the rotation speed of the gears must result in the changes of the input mass flow rate), I could not see any effects in the result. I mean with all of the rotation speeds, I have a constant amount of mass flow rate which is absolutely wrong!!

Thus, I would be so thankful if anybody could have any suggestions enabled me to solve this issue.

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Old   June 19, 2020, 09:58
Default Boundary Conditions
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What conditions are you using at the boundaries?
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Old   June 19, 2020, 10:06
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I use Pressure Inlet and Pressure outlet. Also wall for the outer case and the gears as a solid. The model is 2-D and I also use K-e turbulence model and there is nothing else. In case of dynamic mesh, I use two rigid body for defining the upper and lower gears and also the stationary one for the case of the pump.
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Old   June 19, 2020, 10:09
Default Rotation Speed
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Try with very low rotational speed. The fact is that the flow might be pressure driven and not pump driven. If you get same flow rate even with almost nil rotation speed, then that's what is happening.
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Old   June 19, 2020, 10:15
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Good suggestion. But, actually yes, that's true since we use this external gear pump as a turbine on a high pressure line. The problem is that in the experiments, we record different mass flow rate in different input pressures and so we have different rotation speed!
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Old   June 19, 2020, 10:24
Default Turbine
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Then you should simulate it as a turbine; you may use 1DOF for that. And it will certainly show different speeds at different flow rates.
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Old   June 19, 2020, 10:58
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How could I use 1DOF? should I use it from boundary conditions to add rotational moving wall? or you mean I have to add something in UDF code of "Define-CG-Motion"?
Would you please just extend your explanation a little bit?
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Old   June 19, 2020, 11:29
Default 1dof
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You have to enable 6DOF under Dynamic Mesh and then you can constrain it to 1D rotation within 6DOF settings. No UDF is needed.
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Old   June 19, 2020, 11:32
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I will try it for sure. Thanks a bunch dear Vinerm.


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