Assessment of the lattice Boltzmann method for simulating real-world multiphase flows
Understanding the hydrodynamics of multiphase flows is attractive subject not only for fundamental researches but also for many engineering applications. An accurate simulation of a multiphase system requires tracking interface motion during movement and computing momentum transfer across the interface. Therefore, the development of an effective numerical model can have a large impact on the simulation results. The so-called pseudopotential lattice Boltzmann model (PP-LBM) is extensively applied in multiphase modeling due to its straightforward and computationally efficient algorithm. In order to model a real-world fluid flow when using the LBM, we have to map the physical properties to the lattice (dimensionless) units. This mapping may influence the stability of the model and/or leads to unphysical behavior of the simulated flow (see Fig 1). This is the main reason that the most of the studies available in the literature have selected arbitrary lattice parameters to have stable results. Therefore, the modeled systems are not equivalent with real-world systems.
 
In this project, we aim to explore the capability of the PP-LBM for modeling of a real-world multiphase system. For this purpose, we focus on falling/rising of a physical droplet/bubble with low-density ratio and map the physical properties to the computational parameters to have exact modeling. In order to overcome the drawbacks of the model, the performance of the effective computational factors (such as forcing term, viscosity, 2D vs 3D modeling, and etc.) are examined.
 
Fig 1: Shape time evaluation of a falling nitrobenzene droplet in water with initial size 3mm. According to the experimental results, the nitrobenzene droplet should reach steady state condition with a spherical shape. However, the PP-LBM modeling predicts non-spherical shape.
 
The project is done using developed in-house FORTRAN codes for simulating 2D and 3D multiphase systems. This project is available from September 2016.

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