 In recent years, the development of new electrochemical cells for redox flow batteries (RFBs) has been of great interest. This paper presents the design and hydrodynamic evaluation of differing RFBs geometries, via computational tools, considering that experimental optimization is expensive and highly time consuming. A new geometry, similar to an electrochemical reactor that has a net-like spacer, is proposed as an alternative to conventional design. We applied a theoretical framework provided by the fluid dynamics equations of Navier–Stokes and Brinkman, considering a porous electrode in typical and modified cell geometries. The mass transport was evaluated via tracer molecule distribution at different time points after the tracer injection. The proposed geometry exhibited a more homogeneous flow distribution featuring an increased mean electrolyte velocity inside the electrode (six times higher than in a typical geometry featuring an interdigitated flow field). The increased velocity resulted in shorter retention times. Based on these results, the proposed geometry featuring a net-like spacer is a promising configuration for RFB applications. This work also provides a new approach for developing and characterizing RFBs.