Sdof_obj = Get_SDOF_Object(DT_PU_NAME(dt)) Sdof_prop = 16664*sin(DT_THETA(dt)) /*16,664 is the hydrostatic restoring coefficient*/ Here's a my code:ĭEFINE_SDOF_PROPERTIES(flap, sdof_prop, dt, time, dtime) I've tried writing a UDF for my case so I could apply an external buoyancy force to pull the flap back up to equilibrium, but didn't have any luck. Regarding rotational constraints, I originally set constraints for the rotational angle to -30 and +30 degrees. It's almost like the moment of inertia is causing some sort of torque on the device. I lowered the timestep to 0.001s and still got a negative cell volume because the flap falls over so fast. I changed the water depth to completely submerge the OWSC and the results were even worse. For example, even when I preview mesh motion the flap falls over, so I don't think the waves have an influence on the issue I am experiencing. The only reason I don't believe the natural frequency and wave frequency is the issue is because the flap falls over instantly, even without the presence of waves. I've tried reducing the time step, but nothing seems to be working. The discussion link that I posted above seems to have been inconclusive, and didn't really help my case. However, a moment of inertia this large seems quite unrealistic. When I change the moment of inertia to some large value like 100,000 kgm2, the OWSC doesn’t fall over, and actually begins to act normally by oscillating back and forth as the waves hit it. When I run the simulation with -1500kgm2 as the moment of inertia, the OWSC immediately falls over clockwise.
After trying to isolate the issue, here is what I found: When I run the simulation with +1500 kgm2 as the moment of inertia, the OWSC immediately falls over counter-clockwise. The mass of my device is around 300 kg, and the moment of inertia about the hinge is around 1500 kgm2 according to SolidWorks. The specific issue that I am having is this: whenever I start the simulation using dynamic mesh, the OWSC immediately “falls over” with high velocity. I am currently experiencing an issue with my OWSC model in Fluent 2021, similar to the issue found in this post: Instead of using a UDF, I am using the built in 6DOF solver to assign rotation to the hinge of the OWSC. Hi, I am modeling an OWSC using open channel wave boundary condition and a dynamic mesh.
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