  Given their capability of spreading active chemical species and collecting
electricity, porous media made of carbon fibers are extensively used as
diffusion layers in energy storage systems, such as redox flow batteries. In
spite of this, the dispersion dynamics of species inside porous media is still
not well understood and often lends itself to different interpretations.
Actually, the microscopic design of efficient porous media which can
potentially and effectively improve the performances of flow batteries, is a
still open challenge. The present study aims to investigate the effect of
fibrous media micro-structure on dispersion, in particular the effect of fiber
orientation on drag and dispersion dynamics. Several Lattice-Boltzmann
simulations of {flows through} differently-oriented fibrous media coupled with
Lagrangian simulations of particle tracers have been performed. Results show
that orienting fibers preferentially along the streamwise direction minimizes
the drag and maximizes the dispersion, which is the most desirable condition
for diffusion layers in flow batteries applications.
