Effects of flapping kinematics on odor plume dynamics in low Reynolds number settings

Insects rely on their olfactory systems to detect odors and locate odor sources through highly efficient flapping-wing mechanisms. While previous studies on bio-inspired unsteady flows have primarily examined the aerodynamic functions of flapping wings, they have largely overlooked the effects of wing-induced unsteady flows on airborne odor stimuli. This study aims to explore how flapping kinematics influence odorant transport. Computational fluid dynamics simulations were employed to investigate unsteady flow fields and odorant transport by solving the Navier–Stokes and odor advection–diffusion equations. Both two-dimensional (2D) and three-dimensional (3D) simulations were conducted to visualize the flow fields and odor concentration distributions generated by pitching–plunging airfoils. Our findings reveal that higher Strouhal numbers, characterized by increased flapping frequency, produce stronger flow jets that enhance odor advection and dissipation downstream, while reducing odor concentration on the airfoil surface. In 2D simulations, symmetry breaking at high Strouhal numbers causes oblique advection of vortices and odor plumes. In contrast, 3D simulations exhibit bifurcated horseshoe-like vortex rings and corresponding odor plume bifurcations. These findings highlight the intricate coupling between unsteady aerodynamics and odor transport, offering valuable insights for bio-inspired designs and advanced olfactory navigation systems.