Shell-side friction and mass transfer along bundles of undulated fibers

Computational results are presented for steady, laminar, longitudinal flow along a bundle of parallel, sinusoidally undulating, fibers. In each plane orthogonal to the mean flow direction, the fibers are supposed to be arranged in a regular hexagonal lattice. For a Schmidt number of 500, representative of several solutes, the influence of bundle porosity and of undulation amplitude and wavelength on fluid flow (with special regard to hydraulic permeability) and fiber-fluid mass transfer is investigated by highly accurate and grid-independent finite volume CFD simulations. Although the study is necessarily partial, due to the large number of independent parameters involved, the results indicate a complex and non-monotonic influence of the undulation shape parameters. In particular, moderate undulation amplitudes, of the order of one fiber diameter, yield an enhancement of both permeability and Sherwood number, which can be as high as ∼1.2 and ∼2, respectively, at the lowest porosity investigated (∼0.3).