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Sudden Movement of Spring Loaded Disc Valve at the Beginning of Simulation

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Old   May 13, 2019, 15:01
Default Sudden Movement of Spring Loaded Disc Valve at the Beginning of Simulation
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Onur
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Recently, for my senior project, I have been practicing the Zero Gap model available in Star CCM+. I need to simulate a spring loaded disc valve in order to see its behavior once the flow is initiated. The valve will be the part of a diaphragm pump system which will provide 15 Bars of pressure to another system. (It will be a micro-pump so the valve is considerably small.)

In order to achieve this, I have began by creating a suitable background, overset(circular) meshes with a volumetric control for a better mesh results. The mesh can be seen below on the pictures. I suppose the mesh seems alright once the interface is initialized(need some opinions on this since I have no expertise on what a good overset mesh looks like). It's also a DFBI motion implemented system in which One-DOF Translating Motion is selected. The zero gap system seems to be working fine as the valve 'accidentally' goes through the hole below it with no errors whatsoever.

Here is where the problem starts. Once I initiate the simulation. The valve suddenly jumps up from its initial position to a ridiculous position(can be seen on jumpofthevalve picture). I've tried changing the initial position of the valve, setting the Pressures on Pressure Outlet and Stagnation Inlet to Zero so that no motion will be present. I've also tried to increase the constant "k" of the spring to prevent the jump but nothing worked. What could be the problem??

Here are my boundary conditions:
  • Stagnation Inlet(below): 15 Bars of pressure
  • Pressure Outlet(above): 10-11 Bars of pressure

And my selected Physical Models (Continua):
  • Const. Density
  • Implicit Unsteady: 0.0005s (1st Order) with 12 inner iters.
  • K-Epsilon Turbulence
  • Liquid(Water)
  • Segregated Flow

Also, for my regions, I have set, as stated before, DFBI Translation (Overset) and DFBI Morphing(Background).

Another Note: I tried setting DFBI motion to Free Motion and the valve shoots off like there is no tomorrow. (I guess the pressure is too high but that 0.0005s time step shouldn't be a problem?)

Thank you for your help and time.
Attached Images
File Type: jpg Overset Mesh Results.JPG (77.1 KB, 25 views)
File Type: jpg Overset Mesh Interface Initialized.JPG (83.1 KB, 23 views)
File Type: jpg JumpoftheValve.JPG (46.4 KB, 22 views)
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Old   December 17, 2019, 07:08
Default Any update available?
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Hello Onur,

Are you able to solve this problem. I am working in something similar for 2 way FSI(I'm a beginner in CFD).
Kindly let me know if any updates or references for your study.
Regards,
Vin
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Old   December 29, 2019, 06:58
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Hey,

I have finished my senior project; yet, this is still a continuing project in my school. I would post you the simulation; yet, I cant considering my old pc decided to retire early by giving me a blue screen. (Couldn't recover the files)

To solve this issue, I first tried to make both my overset mesh and background mesh as uniform as possible and equal to each other to allow the cells to 'communicate' between each other as smooth as possible. You can see how it is not uniform near the ends of the domain.

The boundry conditions are very important as well I had some confusion in that too.
Also, I had to do many things considering DFBI motion/morphing as well but I cant necessarly remember since it has been awhile. (The spring constant was messing up the simulation somewhat)

Hopefully this helps a little; I'll try to re-simulate this as I'm also interested in properly simulating this case. I'll keep in touch once I start.
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Old   December 30, 2019, 10:15
Smile Thank you
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Thank you Mr. Onur.
I appreciate it. I will drop a message here if I have any queries regarding the method.
Regards,
Vinay
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Old   January 4, 2020, 07:25
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Hello Onur,
I am also a CFD beginner and very interested in the progress of this project, i try to slove revervsing valve with zero gap model, may be i can help you
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check valve, dfbi morphing, diaphragm pump, overset dfbi

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