Online Seminar on Owls’ aerodynamics during flapping flight by Prof. Roi Gurka
Abstract
Owls’ silent flight have inspired engineers to find solutions for noise reduction applications. The associated mechanisms are partially attributed to their unique wing morphology. During flappingflight, the fluid-structure interaction results in a complex three-dimensional unsteady wake. The coupling between the turbulent wake and the wing motion governs the aerodynamic forces acting on the owl. Understanding of the wake-flow dynamics can elucidate the aerodynamic mechanisms employed by owls during flight and provide insight to the potential reduction of the aerodynamic noise. We study the aerodynamic of owls using various experimental approaches complemented by numerical simulations. Initially, we have flown owls in a wind tunnel. Two owl species were tested: boobook and great horned owl. Both are nocturnal predators, differ in size and habitats. During free flight, the near wake flow field were measured using long-duration time-resolved PIV system and the owls’ kinematics were characterized using high-speed imaging, simultaneously.
Large lift and drag variations over the wingbeat cycle were observed, whilst the drag appeared to be relatively high. The owls near wake did not exhibit any apparent shedding. Instead, a more chaotic wake pattern was observed. Turbulent energy budget at the wake depicted low values of turbulence production compared to relatively high values of dissipation. The pressure field at the wake appears to be suppressed, indicating the presence of a passive control mechanism. In addition, we have simulated the owl flight using DNS. This provided a macroscopic view on the aerodynamic loads exerted during flight as well as microscopic view on the flow manifestation at the boundary layer region in the presence of the owls’ unique features (i.e.: leading edge serrations). Finally, we tested 3D printed models of several owls’ wing species in a wind tunnel using 3D-PTV to shed light on the impact of leading and trailing edge features on the near wake dynamics as well as validate the DNS results. We suggest that owls manipulate the near wake to suppress the aeroacoustics signal by controlling the size of vortices generated and increasing the turbulence dissipation rate at the near wake region.
Short Bio
B.Sc. and M.Sc. at the Faculty of Agricultural Engineering and Ph.D. at the Faculty of
Mechanical Engineering at the Technion IIT, Haifa, Israel; Post-Doc at JHU; Currently, Professor at CCU.
Notice: This event is open to public in respect with the VKI eligibility criteria.
Event Information
Event Date | 06-12-2022 2:00 pm |
Event End Date | 06-12-2022 3:00 pm |
Cut off date | 06-12-2022 11:00 am |
Location | von Karman Institute for Fluid Dynamics |