In this paper, we present a coupled level set moment of fluid method (CLSMOF) for simulating multiphase flows. This method combines the advantage of the sharp interface representation of level set with the highly accurate interface reconstruction from moment of fluid (MOF) method (Dyadechko & Shashkov, JCP, 2008). The MOF method is a superset of conventional VOF method wherein it uses both liquid volume fraction and centroids of each phase in a given computational cell to reconstruct the liquid/gas interface. This method of reconstruction results in a second-order accuracy and also eliminates the necessity of the neighbor cell data requirement for interface reconstruction.

The use of phase centroids helps in determining the orientation of the interface normal which otherwise would have been inaccurate by using only volume fraction or level set functions in under-resolved regions. A directionally split advection algorithm is used for transporting the liquid volume fraction (Weymouth & Yue, JCP, 2010) and the phase centroids are also advected in a directionally split manner using Eulerian Implicit-Lagrangian Explicit (EI-LE) method in our solver ARCHER. A consistent mass and momentum flux computation (Vaudor et al, C&F, 2017) is implemented in our ARCHER.

It has been shown that MOF method (Asuri Mukundan et al, ICCFD10, 2018; Asuri Mukundan et al, ICLASS, 2018) performs better than CLSVOF method (Ménard et al, IJMF, 2007) in terms of accuracy. But due to high computational cost of MOF method, it is imperative to develop a method that has same accuracy and less cost. To this end, we have implemented a new CLSMOF method that uses MOF interface reconstruction method only for those under-resolved thin liquid structures such as liquid ligaments and filaments while using a conventional level set function to reconstruct liquid/gas interface in the domain.

In this work, we have applied this new method for various conventional test cases that include deformation of 2D and 3D droplet, Rayleigh-Taylor instability, and double shear layer with infinite Reynolds number. We have also simulated turbulent round diesel jet using this method. Furthermore, we have shown in this work that CLSMOF method outperforms CLSVOF method. And finally, the CLSMOF method is shown to be computationally less expensive and as accurate as a full MOF method in a given domain of interest in simulating multiphase flows.