calculate time scale for mesh deformation analysis

wilsonbrad · October 23, 2009, 06:54

Am performing pressure relief valve analysis, the problem setup is similar to tutorial 21.I did not find any difficulty while perform tutorial 21.Though I use same boundary condition for my case,after two iterations getting overflow error .. The geometry have clearance between piston and outer surface of the valve is 0.039mm (39 micron gap).

I preferred same time scale which is used in tutorial 21. Am not confident about set the time scale for mesh motion analysis.
Generated the unstructured hexa mesh for entire geometry.

can anyone help me to resolve it

ghorrocks · October 23, 2009, 07:44

Overflow errors usually mean the solver has diverged. This could be due to poor mesh quality, unphysical boundary conditions or poor numerics. To address these issues:
1) Check the mesh quality when it is diverging. If the quality is poor you will need to revise your meshing.
2) Check that the boundary conditions you have are correct. Does it converge if you use a stationary mesh? It will need to converge with a stationary mesh before it will work with a moving mesh.
3) Use a smaller time step or ramp the pressure up to the full pressure over a period of time. Also check your convergence tolerance is OK.

October 23, 2009, 06:54	calculate time scale for mesh deformation analysis	#1
wilsonbrad New Member wilsonbrad Join Date: Oct 2009 Posts: 1 Rep Power: 0	Am performing pressure relief valve analysis, the problem setup is similar to tutorial 21.I did not find any difficulty while perform tutorial 21.Though I use same boundary condition for my case,after two iterations getting overflow error .. The geometry have clearance between piston and outer surface of the valve is 0.039mm (39 micron gap). I preferred same time scale which is used in tutorial 21. Am not confident about set the time scale for mesh motion analysis. Generated the unstructured hexa mesh for entire geometry. can anyone help me to resolve it

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October 23, 2009, 07:44		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,864 Rep Power: 144	Overflow errors usually mean the solver has diverged. This could be due to poor mesh quality, unphysical boundary conditions or poor numerics. To address these issues: 1) Check the mesh quality when it is diverging. If the quality is poor you will need to revise your meshing. 2) Check that the boundary conditions you have are correct. Does it converge if you use a stationary mesh? It will need to converge with a stationary mesh before it will work with a moving mesh. 3) Use a smaller time step or ramp the pressure up to the full pressure over a period of time. Also check your convergence tolerance is OK.