Hi. Could you tell me the process of building dynamic mesh as well as what I should pay attention to. why does nagative volume exist in mesh motion which I can't understand. Hope u out difficulty.

Hi. My current undergrad thesis employs dynamic meshing, but I'm afraid my scope of knowledge might be limited because I have no idea what you want to model. Anyway, negative cell volumes arise because your amount of deformation in the dynamic zone is too large compared to the size of the adjacent cells in the adjacent zones. When a node or edge or face deforms extensively it might flatten/quash the cell to the extent where the moving entity passes through one of the cell's faces, when that happens you get negative cell volumes. The mesh update methods of SMOOTHING(spring), DYNAMIC LAYERING(collaspe or split adj layer based on min height) and LOCAL REMESHING is what Fluent has to offer to get around this problem, but there are inherent limitations to all these algorithms FLUENT employs. The best bet is to reduce your timestep size and increase your number of timesteps, essentially this means more and finer instances of mesh updates within the same physical time change. I hope this helps, for further information, you should read the fluent manual on dynamic meshing. Good luck and enjoy!