Performance portability of lattice Boltzmann methods for two-phase flows with phase change
Résumé
Numerical codes using the lattice Boltzmann methods (LBM) for simulating one- or two-phase flows are widely compiledand run on graphical process units. However, those computational units necessitate to re-write the program by using a low-levellanguage which is suited to those architectures (e.g. CUDA for GPU NVIDIA ® or OpenCL). In this paper we focus our efforton the performance portability of LBM i.e. the possibility of writing LB algorithms with a high-level of abstraction whileremaining efficient on a wide range of architectures such as multicores x86, GPU NVIDIA ® , ARM, and so on. For such apurpose, implementation of LBM is carried out by developing a unique code, LBM_saclay written in the C++ language, coupledwith the Kokkos library for performance portability in the context of High Performance Computing. In this paper, the LBM isused to simulate a phase-field model for two-phase flow problems with phase change. The mathematical model is composedof the incompressible Navier–Stokes equations coupled with the conservative Allen–Cahn model. Initially developed in theliterature for immiscible binary fluids, the model is extended here to simulate phase change occurring at the interface betweenliquid and gas. For that purpose, a heat equation is added with a source term involving the time derivative of the phase field.In the phase-field equation a source term is added to approximate the mass production rate at the interface. Several validationsare carried out to check step-by-step the implementation of the full model. Finally, computational times are compared on CPUand GPU platforms for the physical problem of film boiling.
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