A coupled finite volume-lattice Boltzmann method for incompressible internal flows

We present, test and validate a two-way framework that couples macroscopic and mesoscopic methods to simulate incompressible internal flows spanning a range of spatial and temporal scales. Specifically, the unstructured finite volume method (FVM) is coupled to the structured lattice Boltzmann method (LBM). The multi-resolution domain is resolved through two strategies, i.e., non-Cartesian FVM meshes and multi-level refinement LBM using octree-like Cartesian grid points. The coupled approach divides the entire computational domain into sub-regions, each solved independently. Information exchange between these sub-regions is facilitated by a coupling library that introduces spatial interpolation and temporal iteration schemes for different scales. The effectiveness of the proposed coupled strategy is assessed against well-documented benchmark tests and further examined in scenarios involving flow over artificial porous media. The results obtained by the new coupled framework show excellent agreement with reference data and exhibit strong parallel performance for tests on up to 32768 CPU cores, demonstrating the potential of the approach for large-scale investigations. Program summary: Program Title: code_saturne-LUMA-coupling CPC Library link to program file: https://github.com/yangzhou-10/code_saturne-LUMA-coupling LUMA licensing provisions: Apache License 2.0 LUMA programming language: C++ code_saturne licensing provisions: GNU General Public License v2.0 code_saturne programming language: C, C++ Nature of problem: Traditional single CFD numerical methods face significant challenges in multiscale flow simulations. Numerical methods, relying on the continuum medium hypothesis, often overlook or approximate microscale effects using empirical schemes. Conversely, micro/mesoscopic methods are constrained by the computational resources required to simulate the entire domain comprehensively. Solution method: A coupled FVM-LBM scheme is developed wherein the computational domain is partitioned into macroscopic and microscopic sub-regions, solved independently using the FVM and LBM, respectively. Communication between these sub-regions is facilitated via a coupling interface implemented using the PLE coupling library. The LBM code is developed within the LUMA package, while the FVM code is integrated into the framework of code_saturne. The PLE coupling library is embedded within the code_saturne package.