Effect of wavelength in seal-whisker inspired undulated cylinders

While hunting for prey, seals are able to use their whiskers for hydrodynamic trail following, a skill partly attributed to the unique shape of the whiskers themselves. The whisker's undulated topography has thus been investigated for its hydrodynamic properties, demonstrating reduced drag and oscillating lift forces when compared to flow over a smooth cylinder however the exact mechanisms are not well understood. The current investigation parameterizes the seal whisker inspired undulated geometry into seven non-dimensional parameters and shows that individual modifications to the geometric parameters can strongly impact the overall flow response. In particular, simulations are performed for flow over five geometries with various undulation wavelengths (λ=1, 2, 3.4, 5, 6.9) and a comparable smooth elliptical cylinder. The effect on wake patterns and spanwise variation is investigated through comparison of Reynolds stresses and turbulent kinetic energy calculations. Changes in the flow response vary nonlinearly with respect to topography wavelength with minimal drag and oscillating lift occurring at a biologically relevant wavelength, λ=3.4. The analysis highlights the redirection of energy along the span and the resulting effect on wake structure and vorticity.