Hi everyone! I have the following problem. I have a two phase flow in a circular pipe and I want to model it. I need to decide and justify whether the model should be 2D or 3D. For the moment, I can say only one thing: considering z-axis in the lenght direction (that it is the dominant one) I have to neglect x or y. If I do this, I suppose I would loose the circularity of the pipe because I consider x or y as the elongated direction, obtaining something more similar to the flow between two flat plates. Then, probably, I need a 3D approach. What do you think about it? Do you have any suggestions? What other things could I loose if I choose a 2D model? Thank you very much!