The cochlea is our fluid-filled organ of hearing with a unique spiral shape.
The physiological role of this shape remains unclear. Previous research has
paid only little attention to the occurrence of transverse flow in the cochlea,
in particular in relation to the cochlea's shape. To better understand its
influence on fluid dynamics, this study aims to characterize transverse flow
due to harmonically oscillating axial flow in square ducts with curvature and
torsion, similar to the shape of human cochleae. Four geometries were
investigated to study curvature and torsion effects on axial and transverse
fluid flow components. Twelve frequencies from 0.125 Hz to 256 Hz were studied,
covering infrasound and low-frequency hearing, with mean inlet velocity
amplitudes representing levels expected for normal conversations or louder
situations. Our simulations show that torsion contributes significantly to
transverse flow in unsteady conditions, and that its contribution increases
with increasing oscillation frequencies. Curvature has a small effect on
transverse flow, which decreases rapidly for increasing frequencies.
Strikingly, the combined effect of curvature and torsion on transverse flow is
greater than expected from a simple superposition of the two effects,
especially when the relative contribution of curvature alone becomes
negligible. These findings could be relevant to understand physiological
processes in the cochlea, including metabolite transport and wall shear
stresses. Further studies are needed to investigate possible implications on
cochlear mechanics.Comment: 26 pages, 7 figure