hi, i use dynamic mesh in my model of a sway tank. the tank is filled with water.

i load a time-dependent angular velocity to the tank walls.

then, i set the time step 4e-5, and after 500 steps, the warning is shown: Warning: negative cell volume detected! Error: Update dynamic mesh failed! Error Object: ()

anyone could tell me what is the problem. thanks in advance!

I'm not quite sure of that. but i guess your dynamic mesh has been deformed or squeezed until the edges of some or all the cells has interfered within the same cell. this is the definitions of the negative cell volume error. you need to improve your initial mesh to be not too angular and use structured mesh if possible. also you may increase the mesh size to account for the deformation displacement during the iteration until reaching the convergence without having negative mesh. I hope this will help

thank you very much! i will have a try.

are you using layering/smoothing or remeshing method for the dynamic mesh?

Try with smaller time step or use a triangular mesh as it is better for MDM simulation. If this still does not work, you have to check your parameters in defining MDM.

Sham

[Amit soni]

Updating mesh to time 2.00000e-02 (step = 00002)...
Dynamic Mesh Statistics:
Minimum Volume =-1.30210e-01
Maximum Volume = 1.37794e+00
Warning: negative cell volume detected!
Error: Update dynamic mesh failed. Negative cell volume detected.
I am also getting this , would you guide regarding this?

[coolmech24]

Originally Posted by Amit soni

Updating mesh to time 2.00000e-02 (step = 00002)...
Dynamic Mesh Statistics:
Minimum Volume =-1.30210e-01
Maximum Volume = 1.37794e+00
Warning: negative cell volume detected!
Error: Update dynamic mesh failed. Negative cell volume detected.
I am also getting this , would you guide regarding this?

Amit I suppose you are using moving mesh.
problem with this is if you solve moving mesh problem once mesh moves and if you discard solution mesh will not retain original state so when you try to solve it again it will give negative mesh error. to remove it you need to reset "solution" using right click in workbench project menu. after reset you can solve again.

[Hooman.Fa]

Hi everyone.
I have a really fatal error in my simulation. i'm working on a submarine with 16.4m model length. I use dynamic mesh for 6-DOF and remeshing (local cell is enabled), layering (split factor=0.5 , collapse factor=0.2) and smoothing (spring constant factor is 1E-5 & number of iteration is 100) are enabled. also my mesh is concluded both structural mesh for far away the model and nonstructural near the submarine model (11724000 mesh elements). I have used a UDF code for 6-DOF to determine the model properties. The time step value is set to 1E-4. URF for pressure is 0.05 and in advanced solution controls for pressure I've used V-cycle with BCGSTAB stabilization method and for x,y,z momentum flexible termination is set.
after 70 time steps (3500th iteration) i got an fatal error : Negative volume cell detected.
can anyone help me please? I'm really stuck in a bad situation.
thank you so much.