Ansys Fluent: Forced Pendulum

[@jingzhang9672]

I can't repeat your animation per your tutorial. My animation is not the same. The velocity of the pendulum can't be reduced by the inlet pressure. I don't know why. Also, your setting of the inlet to dynamic mesh is wrong.

[@fluentsetup1232]

Can you elaborate on what is different on your animation and the setting of the dynamic mesh?

[@jingzhang9672]

​@@fluentsetup1232 Thanks for your reply. Everything is the same as your tutorial except setting inlet1 to dynamic mesh (timeline 11:35), which is probably a mistake. That will change the position of the inlet1. My animation has no obvious pressure force effect on the pendulum. That means the velocity of the pendulum can't be reduced by the pressure of inlet1 & inlet2. It is more like a pure simple harmonic movement without pressure effect. I validated my guess by adjusting the position of the pendulum to be vertical to remove the gravity effect. The result is that the pendulum stays static. The inlet 1 & inlet 2 can't move the pendulum at all. Several validations were done to check this problem. I found my problem is that I can't load any pressure force on the dynamic mesh, neither rotation nor translation. My dynamic mesh can only move by gravity. I don't know why. Could you help me to fix this?

[@jingzhang9672]

Please see my animation. kzbin.info/www/bejne/jaPYmqydhKmNo7M

[@jingzhang9672]

​@@fluentsetup1232 Problem was fixed. One mistake setting per your tutorial (11:26), which deleted the dynamic mesh of PendulumWall. That causes no pressure force on the PendulumWall surface. Thanks for your great video. I like it.

[@fluentsetup1232]

@@jingzhang9672 Sorry for the late response, and thanks for the clarification. I don't know how I didn't see that mistake before.

[@aleyhaider9038]

Very very thankful to you 🙏🙏🙏🙏

[@ingwilliamsanabria4341]

This modeling is possible in 3D? Thanks for you answers

[@dhrubap-jq6ys]

Great tutorial. Actually new to fluent. How did you find the CG and moment of inertia in ansys?

[@alfaageng]

Do you have any videos of moving nozzle in translation motion?

[@daniyarbossinov5951]

How do you defined moment of Inertia?

[@fluentsetup1232]

In timeline 11:35, you should reeplace the 'inlet1' wall with the 'pendulumwall' wall, otherwise you would be moving the inlet.

[@jingzhang9672]

One more question. There is one tutorial said that "To use the Six DOF solver for this kind of application, the CG must be used as the center of rotation. Fluent evaluates the forces acting on the surface on a cell level, using the distance from each facet center to the CG to calculate the moment. This applies to all forces except gravity." That confused me. How do you understand this? Thanks.

[@fluentsetup1232]

I read it as, in order to compute the moment on the object, the forces are computed in every element, on every wall that is in contact with said object, then multiplied by the distance respect to the center of rotation, then added up. What I find strange is that it says the center of rotation and the center of gravity must coincide, which seems somewhat restrictive on the number of simulations you can actually run on Fluent using the dynamic mesh tool. May I ask where you got that info from?

[@jingzhang9672]

@@fluentsetup1232 KZbin keeping delete my comment with the link. So I added it into the "DISCUSSION" of your channel and my channel. What confused me is that it says Fluent applies to all forces except gravity, which seems a pendulum will stay static if only applying gravity (that is not true obviously). It sounds like it's a bug of Fluent as the tutorial said. We have to add an additional moment to represent the gravity effect for the off-centered case.

[@fluentsetup1232]

@@jingzhang9672 That sounds weird, I've tried the pendulum with gravity and viscous resistance being the only two forces and it seems to work just fine.