Numerical modeling of a simplified alkaline water electrolyzer with code_saturne

Purpose This work aims to develop and validate an open-source, multiphysics computational fluid dynamics (CFD) model in Code_Saturne for the numerical simulation of a simplified alkaline water electrolyzer to quantify how electrode–membrane spacing, temperature and gas production affect polarization and efficiency. Design/methodology/approach A segregated, cell-centered finite-volume solver is used with a homogeneous-mixture formulation for gas generation, Tafel electrode kinetics, energy coupling and a cell-centered flux-reconstruction to treat discontinuous conductivities at interfaces. Mesh sensitivity and parametric studies (spacing, temperature, applied voltage / current) are performed. Findings The model reproduces reference polarization curves with high fidelity; pointwise relative error remains below 2% for current densities > 1000A m² and CFD-predicted outlet gas fractions agree with Faraday-based estimates within approximately 3%. A mesh study identified a 100 µm bulk cell (first-cell 100 µm, approximately 7000 cells) as a pragmatic reference. Ohmic losses scale almost linearly with electrode–membrane spacing and thermoneutral efficiency decreases from 75% at low currents to 53%–64%. Originality/value This work presents a validated, open-source implementation of a homogeneousmixture electrolyzer model in Code_Saturne together with practical numerical best-practices and quantitative insight into spacing effects on performance.