###### Abstract
The concentration overpotential, \(\eta_{C}\), can become the dominant term in this situation. The limiting current density in this limiting case, \(i_{L}\), is then expressed as shown in Equation (2) [4]:  
\[i_{L}=nFk_{m}C_{b} \tag{2}\]  
where \(n\) is the number of electrons in the reaction and \(C_{b}\) is the bulk reactant concentration in mol m\({}^{-3}\). The local mass transfer coefficient, \(k_{m}\), in m s\({}^{-1}\) is a function of convective fluid velocity, \(v\), in m s\({}^{-1}\) as shown in Equation (3) [4]:  
\[\text{k}_{m}=1.6\times 10^{-4}\cdot v^{0.4} \tag{3}\]  
Considerable attention has been devoted to the development of new cell materials, electrodes and reaction mechanisms [5], while electrolyte flow and the associated mass-transfer effects remains to be satisfactorily addressed [6]. Without turbulence or mechanical interventions, diffusion-limited flow conditions result in reactants being depleted close to boundaries. Cell design aimed at this issue predominately use fuel cell-inspired flow fields, particularly interdigitated and serpentine channels [7], despite pressure drop challenges associated with scaling up to industrially relevant battery stack sizes [8]. Commercial scale cells rely on traditional flow-through configurations as the parasitic pressure drop associated with interdigitated and serpentine flow fields remains too high. Assessing larger cells is thus key for implementation, although experimental work on cells at that scale is more difficult, especially when the goal is to examine internal phenomena. Simulation with numerical models provides a more accessible means, and have been used since [PERSON] and co-workers published their dynamic two-dimensional models [9; 10; 11]. Researchers have since developed more versatile coupled mechanical and electrochemical models. [PERSON] et al. [12] published a simplified stationary model, which was then adapted to a three-dimensional domain [13]. Other groups have included considerations such as vanadium crossover and water transport between half-cells [14]. Novel cell geometries, including trapezoidal [15] and radial designs [16], have been explored with the aid of these models, helping to show the potential of design modifications for flow-through cell performance enhancement. Unfortunately, initial research into these particular designs found them to be susceptible to uneven distribution across the cell and increased pressure drop through the cell. An alternative approach, involving progressive reduction of the cross-sectional area to provide increased electrode compression and higher flow rate towards the outlet, showed it is possible to improve both electrochemical and mechanical performance with innovative design [17]. Subsequent experimental testing on laboratory-scale cells demonstrated improved energy efficiencies with wedge shaped cells, and a toroidal stack concept based on this concept was presented at the International Flow Battery Forum [18]. The effect of felt compression has been well documented [19; 20] and other studies have applied the same theory in different ways, such as by modifying the materials instead of the cell geometry [21; 22; 23]. Another group has modified the cell architecture with asymmetric compression to address species crossover and associated capacity decay [24]. The problem of concentration gradients across the half-cell cross-section between the solid current collector and the membrane persists with these innovations and others like the circular concept proposed by [PERSON] at al. [13; 25]. The application of static mixers has been proposed to address this problem [26], but not in conjunction with varied compression. Conductive static mixers have previously been used in experiments with slurry electrode VRBs [27] and other electrochemical flow cells [28]. Subsequent research with inert mixers and conventional electrolytes showed enhanced electrochemical performance with a small pressure differential.