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6DOF - 1DOF translation large forces

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Old   February 15, 2018, 16:23
Default 6DOF - 1DOF translation large forces
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Emil Pedersen
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Hi all,

So im new to fluent, and i want to simulate the opening of a check valve by simulating a spring force on one face of the valve and the fluid pressure on the other. I want to do this in 2D
I have set this up with the 6DOF solver and set it to 1DOF translation with a small spring constant of 20N/m. The fluid is water, and i've set a velocity inlet based on a UDF where the flow is = 10*current_time, up until 0.02s when the flow is 0.2m/s. The outlet is a pressure outlet with 0pa static pressure.

My problem is that unless i use very very small time steps of 1e-10 s, even at very small flow rates, the solver spits out huge resulting forces on the face of the valve. This only happens for fluids with high densities, if i use air for example, i am able to simulate the valve movement just fine.

What could the issue be?

i have uploaded a pic of the pressure contour. The inlet is to the left. This is at a time step in the order of 1e-09 seconds.
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Old   February 18, 2018, 07:19
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Quote:
Originally Posted by FluidEmil View Post
Hi all,

So im new to fluent, and i want to simulate the opening of a check valve by simulating a spring force on one face of the valve and the fluid pressure on the other. I want to do this in 2D
I have set this up with the 6DOF solver and set it to 1DOF translation with a small spring constant of 20N/m. The fluid is water, and i've set a velocity inlet based on a UDF where the flow is = 10*current_time, up until 0.02s when the flow is 0.2m/s. The outlet is a pressure outlet with 0pa static pressure.

My problem is that unless i use very very small time steps of 1e-10 s, even at very small flow rates, the solver spits out huge resulting forces on the face of the valve. This only happens for fluids with high densities, if i use air for example, i am able to simulate the valve movement just fine.

What could the issue be?

i have uploaded a pic of the pressure contour. The inlet is to the left. This is at a time step in the order of 1e-09 seconds.
hi
show boundary conditions on the picture
when you used air, have you seen the valve seat moves?
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Old   March 5, 2022, 09:40
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Hi
I have the same problem. In every time steps force value going to infinity.
I'm so glad if someone help me.
Thanks
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Old   March 5, 2022, 18:16
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Marcin
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Try solution stabilization.
In dynamic mesh panel, for the selected zone (I guess, wall absorbing the pressure forces), you will have a panel called Solution stabilization, try the volume based, starting from small Scale factor values
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Old   May 15, 2024, 06:02
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How to use damping in the 1DOF spring case??
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