code_saturne User's Forum

Hello,

I want to use the ALE method for the simulation of a flow between two cylinders (annular cavity). The mesh is attached above. The problem, is that the program can't start the calculation, in other words it stops at the first time step. The error messages i'm obtaining (2 error messages), are also attached to the mail. Please can you help me to understand more these messages, so i can solve the problem once for all.

Thank you for your help.

Nazir Al Sayed.

Hello,

The problem seems to be due to the fact that at least one cell is so distorted by the mesh deformation that its volume becomes negative (the cell becomes "entangled"). This is not always easy to solve, but you may first try to visualize the deformed mesh to see "how much" it was distorted.

Reducing the time step, increasing the mesh viscosity, and/or changing boundary conditions (prescribing a boundary velocity instead of deformation, or vice versa) may help. Some recent developments (that should appear in version 2.2 I believe) should make the ALE more robust, but for version 2.0, I am not aware of many other solutions.

Best regards,

  Yvan

Hello,
I decreased the time step , as you have reported. It works well now, there is no volumes negative . T hank you very much.

Nazir

Previously Nazir Al Sayed wrote:

Hello,
I am trying to solve your problem , I am getting error (negative control volume) in 1st time step itself
Even I am  decreased the time step as you did. Its not working here , showing "abort due to volumes negative ."
Can you please help me out of this.
T hank you very much.

theja