Flow over a bio-inspired wavy elliptic cylinder at a subcritical Reynolds number of 3 × 103

The unique morphology of seal whiskers can significantly reduce drag and fluctuating lift forces. Inspired by this, large eddy simulations and water tunnel experiments of the flow around a seal-whisker-inspired, simplified wavy elliptic cylinder are conducted at a subcritical Reynolds number of Re = 3 × 103. The spanwise wavelength (λ) of the wavy elliptic cylinder covers a wide range of 0.5 ≤ λ/Dm ≤ 8, with a fixed wave amplitude of a/Dm = 0.1, where Dm is the mean hydrodynamic diameter of the wavy elliptic cylinder. Based on variations with λ/Dm in time-mean drag, fluctuating lift, Strouhal number, vortex formation length, and wake topology, the flow around the wavy elliptic cylinder is classified into four distinct regimes, i.e., I–IV. A comprehensive examination is made for each regime, including instantaneous and time-mean flows, Reynolds stresses, and turbulent kinetic energy distributions. Results indicate that, compared to the baseline straight elliptic cylinder, the wavy elliptic cylinders with λ/Dm = 3 and 4 in flow regime II can reduce time-mean drag and fluctuating lift by 12.5% and 86.6%, respectively; meanwhile, significant force reductions are observed in flow regimes III and IV. The performance is associated with the emergence of hairpin-like vortices in instantaneous flows, significant increases in vortex formation length, distinct flow bifurcations, and substantial reductions in Reynolds stresses and turbulent kinetic energy in the near wake. It is also noted that, similar to the wavy circular cylinder, the spanwise variation rate of the vortex formation length of the wavy elliptic cylinder is a key parameter influencing the near wake flow.