What is the difference between alpha.water and alpha.water.orig in the files of the i
 

Hello, I'm new to openfoam. What is the difference between alpha.water and alpha.water.orig in the files of the interfoam decoder and what is setFieldsdict and how can I customize this file?
I will be grateful if you could help me :)

Hello,

setFields is an utility to initialize fields values. It is typically used with VOF solvers to define a volume of water inside the domain. (eg: set alpha.water to 0 everywhere in the domain, and define a box where you will set alpha.water to 1 in order to have a volume of water as your initial state)

When doing something like this, setFields will update the alpha.water file according to what is defined in system/setFieldsDict. If you want to preserve the original file before it gets updated by setFields, you need to make a copy of it. This is what alpha.water.orig is. The original alpha.water file that you can use to start over.

Cheers,
Yann

Thank you very much for the information.

I have a complex geometry file with .stl and .step extensions. I want to put this geometry into a boundary volume and perform VOF analysis. I want the object to move in this limit volume. How will I define the complex geometry here into the setFieldsdict file? This is easy for simple geometries, but how can I achieve this in complex geometries?

setFields is only used to define fields values, not a geometry.

You will have to mesh your object according to the simulation you want to perform. Depending on the motion of your object, you might need to use different mesh motions techniques and it will have an impact on how you should create your mesh.

Can you elaborate on the simulation you try to achieve?

Consider a boundary volume entirely covered with water, which eventually opens into the atmosphere, or the boundary volume may be half filled with water and half filled with air. I want to place a complex part in the water-filled part of the boundary volume and run this analysis. This piece will move at a certain speed and reach the atmosphere

Alright, then I suggest to have a look to dynamic mesh.

There are different techniques implemented in OpenFOAM to deal with object/mesh motion. The proper technique depends on the simulation you want to do. (what kind of motion if involved? Do you want to prescribe the motion of the aircraft or to simulate its motion due to buoyancy?)

Anyway, setFields has nothing to do with that.

I want to determine the movement of the piece and at the same time I want to view where this piece will fall. So I don't need to define this part in the setfieldsdict file, right? Another question I have is that I am applying the following mesh process in Salome. Do I need to remove my piece from the boundary volume? I would really appreciate it if you could help me and guide me in this context.

Let me explain my problem again. Imagine that the inside of a boundary volume is air, and there is a solid object inside. This object should not be deformed as it moves. I want to calculate where this piece will move and fall within the boundary volume. I want to apply the mesh operation on Salome.

Let me know if I understand well: you want to compute the motion of your object free falling, right?

I have a certain speed on the x and y axis, I want to calculate where it will fall.

At the same time, I want to display the movement of this object depending on time on paraview.

If you have large motion of the object relatively to your domain, or complex motion, you may have to go for overset (https://doc.openfoam.com/2306/tools/...erics/overset/)

If motion is not to big, morphing mesh might do the job.
Search for dynamic meshes on OpenFOAM, there are some resources online explaining the different techniques.

If you go for overset, the meshing process won't be straightforward and you probably won't find an example doing exactly what you want. If you are totally new to OpenFOAM you will probably have to understand the basics before being able to setup your case.