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Abaqus co-simulation - pressure instability

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Old   January 10, 2015, 06:36
Default Abaqus co-simulation - pressure instability
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Josef Camilleri
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Hi all,

I am trying to model the impact of a 2D elastic plate (a slice of the panel representing the centre span) with water using Star CCM+ coupled with Abaqus. The plate, inclined at an angle of 10 degrees, is fixed in space and the free surface moves with a constant upwards velocity (1m/s) towards the plate. The free surface is initially 1cm below the plate.

I am using the mesh morphing model to account for the plate deflections. I applied a symmetry BC condition at the front and back faces and the LHS tank wall of the fluid domain (2D slice), velocity inlet at the bottom, pressure outlet at the top and a wall BC at the RHS wall of the tank and the plate. I am using a fixed plane morpher condition at the bottom, top and tank wall RHS and an Abaqus co-simulation BC on the plate. The symmetry BCs automatically adapts a symmetry-plane condition for the morpher.

I first run the simulation with the Abaqus Co-simulation and Mesh Morpher solvers switched off until the pressure field stabilizes (when I start the simulation, the pressure field is very unstable and the probes on the bottom of the plate record very high pressure values, which I think is because of some sort of singularity in the solution?). After that, I stop the solution, clear it (with the Fields and Reset Mesh boxes unticked), switch on the Abaqus Co-simulation and Mesh Morpher solvers, initialize the solution and run it again. The problem is, when I run it again, the pressure field looks very unstable (see Figures). At this point the free surface is still way below the plate and no plate deflections take place (hence minimal or no mesh deformation). After the plate impacts the free surface (at about 1/3 immersion) the pressure field becomes extremely high and the solution crashes because of negative volumes. The negative volumes part I can understand, and need to work on it, but the unstable pressure field while the plate is in air, that I can't figure out what is causing the problem. I have tried different pressure, velocity and grid flux URFs, 1st and 2nd order time schemes but nothing seems to work.

Does anyone have an idea of what might be causing the problem? If you need more information about my model please do not hesitate to ask. Please not that I have run both CFD and Abaqus models independently and both work fine. Thank you for your time.

Best regards,

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File Type: jpg Instable pressure field (1).jpg (28.6 KB, 17 views)
File Type: jpg Instable pressure field (2).jpg (30.2 KB, 13 views)
File Type: jpg Instable pressure field (3).jpg (29.5 KB, 14 views)
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Old   July 9, 2015, 08:07
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are you working on Mesh morphing using abaqus co simulation ? Actually im working on the same problem. But in my case im using displacement values in table format and giving that as input for morphing.

I would like to ask you, is it possible to specify the required deformation in abaqus and then simulate in starccm+?
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