## Fluids

Topics relate to Fluent, CFX, Turbogrid and more

#### Expanding Mesh Fluent

• agion
Subscriber

Hi all, I am brand new to the world of ANSYS and any multiphysics modeling in general.  I am trying to set up a simply dynamic mesh problem to simulate crystal growth (I am a geologist by training).  Essentially I have set up a problem with a small cube (a crystal) inside of a large cube (growth medium) and the small cube grows at the expense of the large cube.  I am having problems getting the smaller cube to grow in size.  I've been able to set up the geometry, create a mesh, interfaces etc. but am struggling with the setting up the dynamic mesh. I think I need to use a deforming mesh but I'm not sure.  Are there any tutorials that explain a related problem, or does any know of a simple way to set this up?

• Raef.Kobeissi
Subscriber

Hi,

• agion
Subscriber

Raef,

Thank you for the help.  I watched the video and I had a second question about the velocity profile.  Is it possible to write a profile that results in motion in 6 directions (x,-x,y,-y,z,-z)?  I want to have the mesh grow an equal amount all directions.

• Raef.Kobeissi
Subscriber

Hello yes it is possible writing the right UDF.

• Raef.Kobeissi
Subscriber

It is difficult to help writing it without knowing the parameters

• agion
Subscriber

Raef,

Ideally the I would like the UDF to increase the size of the cube in each direction equally.  For instance if there the cube is 1x1x1 cm at t=0 advancing through, say 5 steps, would result in a cube that is 6x6x6, resulting in a motion 1 cm/s.  This is just an example of the type of thing I am looking for. I was able to write individual udfs for each direction, but I am not able to increase the surface area of the cube.  I wind up with 6 faces separated by a distance.  At some point the model crashes and gives me the error that negative geometry has been detected.  I hope this clarifies things a bit.  I am still getting the basics down so my understanding is still limited.

• Raef.Kobeissi
Subscriber

Did you try to use unstructured mesh? Triangular/tetrahedral?

cheers