Abstract: Addressing global challenges such as the depletion of fossil fuels and environmental pollution requires the development of clean energy for sustainable development. Hydrogen energy, with its zero-carbon emission and broad applicability, is considered a key pathway to reshape the future energy landscape. Alkaline water electrolysis, a key technology for clean energy production, is widely used due to its low equipment cost and relatively mature technology. However, conventional electrolyzer designs still face significant challenges, including liquid separation efficiency, high polarization losses, and uneven flow distribution, which limit the overall energy efficiency and operational stability of the system. Therefore, optimizing the electrode structure and fluid flow configuration to reduce local overpotential and enhance bubble detachment efficiency is crucial for improving the performance of the electrolyzer. The expanded mesh turbulence-inducing structure has attracted widespread attention in alkaline water electrolyzers due to its excellent flow-guiding capability and ease of fabrication. The shape, size, and arrangement of its mesh openings determine the flow path of the electrolyte, influence bubble generation and migration, thereby regulating the uniformity of the electrochemical reactions and overall system performance. The major axis length, minor axis length, and height of the mesh units are easily adjustable parameters in both flow channel design and mesh fabrication, forming the basis for structural optimization and parametric investigation of expanded mesh. To gain deeper insights into the coupled mechanisms of mass transfer, heat transfer, and electrochemical reactions within alkaline electrolyzers, and to enhance both system performance and structural design, this study examines electrolyzers with expanded mesh structures. This study systematically investigates key design parameters, including geometric factors (mesh opening slope length, minor axis length, and mesh height) and flow configurations (flow direction), using a multiphysics coupling approach. A three-dimensional multiphysics model is developed that integrates two-phase gas–liquid flow, heat transfer, and electrochemical reaction processes to clarify the interactions among the complex physical phenomena inside the cell. The numerical study consists of three main steps: electrochemical initialization, coupled simulation of the flow and thermal fields, and post-processing analysis. The results reveal the influence of structural variables on bubble removal efficiency, local current density distribution, and system pressure drop. Reducing both the major and minor axis lengths increases current density; moderately lowering the mesh height enhances flow disturbance and gas removal; and adopting counter-flow configurations promotes bubble detachment, thereby improving electrolysis performance. At an applied voltage of 2 V, the counter-flow arrangement achieved a 6.2% higher current density than the co-flow configuration, demonstrating superior electrochemical performance. Reducing the major and minor axis lengths increased the current density to 417 mA·cm⁻² and 422 mA·cm⁻², corresponding to improvements of 9.1% and 13.7%, respectively. The optimal mesh height yielded a current density of 420 mA·cm⁻², representing enhancements of 14.4% and 11.4% compared to excessively high and low mesh heights, respectively.