The major two phase flow regime in the micro tubes is the Slug flow regime. In this case there is one or few bubbles inside the channel. Hence, it is usually using surface tracking techniques for simulation of two-phase flow in micro tubes.
Many different phenomena in industry or nature include a deformable interface for example the water falling from a spillway. The simulation of such events is essential to better understanding of two-phase flow behavior, in order to optimize the design or to calculate hydrodynamic coefficients. The precise and correct modeling of the interface is the key parameter in the simulation of a free surface. There are different interface tracking methods such as VoF (volume of fluid), LS (level set), and FT (front tracking). Each method has its own advantages and disadvantages, however, VoF is becoming the most common interface tracking method due to its ease of implementation and mass conservation. OpenFOAM VoF solver is interFoam. The solver uses a technique called MULES to compress the interface and return the sharp interface. The interFoam is suitable for two-phase isothermal incompressible system. The derived solvers from interFoam is:
As a part of my Ph.D. thesis, I extended an OpenFOAM solver interFoam to consider mass transfer due to boiling and condensation, new solver is called phaseChangeHeatFoam. It is available in git, it can be downloaded and compiled with the following commands in a Linux terminal.
git clone https://github.com/NimaSam/phaseChangeHeatFoam/
chmod +x All*
I wrote the first edition of OpenFOAM book around 5 years ago in Persian. The book was based on OpenFOAM-1.6. The aim of that book was to shorten the process of OpenFOAM learning. It was 5 chapters that included some simple and introductory examples. It covered different parts of OpenFOAM utilities, solvers and programming.