# 6DOF - 1DOF translation large forces

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February 15, 2018, 16:23
6DOF - 1DOF translation large forces
#1
New Member

Emil Pedersen
Join Date: Feb 2018
Posts: 1
Rep Power: 0
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.
Attached Images
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February 18, 2018, 07:19
#2
Member

ram
Join Date: Apr 2013
Posts: 37
Rep Power: 13
Quote:
 Originally Posted by FluidEmil 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?

 March 5, 2022, 09:40 #3 New Member   mohammad Join Date: Dec 2021 Posts: 10 Rep Power: 4 Hi I have the same problem. In every time steps force value going to infinity. I'm so glad if someone help me. Thanks

 March 5, 2022, 18:16 #4 Member   Marcin Join Date: Jun 2016 Posts: 96 Rep Power: 9 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

 May 15, 2024, 06:02 #5 New Member   CFD Join Date: May 2022 Posts: 14 Rep Power: 4 How to use damping in the 1DOF spring case??

 Tags 6dof, check valve, large force