| Summary: | Numerical simulations are a vital tool for understanding gas-liquid two-phase flows, and robust numerical methods are essential for this purpose. In this regard, a code library was developed using C++ for the numerical simulation of three-dimensional gas-liquid two-phase flows and heat transfer. The code is written based on a framework of numerical methods namely; Volume/Surface Integrated Average-Based Multi- Moment Method (VSIAM3) including Constrained Interpolation Profile-Conservative semi-Lagrangian (CIPCSL) methods, Coupled Level-Set and Volume-of-Fluid (CLSVOF) method, and density scaled CSF model. VSIAM3 is a numerical method for compressible and incompressible flows based on the multi-moment concept. VSIAM3 employs CIP-CSL schemes for solving the conservation equation. The CLSVOF is an interface capturing method that is well suited for two-phase flows with surface tension. The density scaled CSF model is used for the surface tension computation. An efficient implementation of the numerical methods was investigated through the discretisation techniques of the conservation equation in VSIAM3. These techniques were studied through the lid-driven cavity, shock tube problems, two-dimensional explosion test, and droplet splashing on a superhydrophobic substrate. It has been found that the use of a less oscillatory CIP-CSL method is essential for robust numerical simulation of compressible and incompressible flows using VSIAM3 and that the numerical results are sensitive to the discretization techniques of the velocity divergence term in the conservation equation. A parallel code library was also developed using Open MPI (the Message-Passing InAbstract iv terface) for the three-dimensional numerical simulation of gas-liquid two-phase flows and heat transfer. The parallel performance has been evaluated, and a good scalability was obtained. The code library was further validated through the numerical simulation of equilibrium drop, single rising bubble, Kelvin-Helmholtz instability, and turbulent channel flow. The numerical results were reasonable. Validations of VSIAM3 for heat transfer problems were also conducted through singlephase and two-phase Rayleigh-Benard convection. We found that solving the diffusion term of the Navier-Stokes equation and the conduction term of the energy equation for all the moments in VSIAM3 is essential for robust numerical simulation of heat transfer problems using VSIAM3. In addition to that, using Time Evolution Converting (TEC) for computing the boundary values of the temperature in VSIAM3 as suggested in the literature influences the robustness of VSIAM3. In conclusion, an efficient implementation of VSIAM3 for gas-liquid two-phase flows and heat transfer using VSIAM3 and CLSVOF was developed and validated through single-phase and gas-liquid two-phase flows and heat transfer problems. The established code library is suitable for the numerical simulation of gas-liquid two-phase flows and heat transfer.
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