Meeting Abstract
The fluid dynamics of the flapping flight of owls is studied experimentally and numerically. We analyzed a great horned owl, a tawny owl, and a Harris hawk. The latter was chosen to carry out a comparative analysis with the similarly-sized great horned owl. We conducted high-speed, long-duration time-resolved PIV experiments in an open wind tunnel. A perch-to-perch flight style was chosen, and multiple flights were performed for all the birds. High-speed cameras synchronized with the PIV were utilized to capture the kinematics of the birds from different views during flight. The kinematic images display a similar flight path for the three birds, while a comparison of the wake characteristics shows similarities between the two owls and a distinct difference for the hawk in terms of wake flow patterns and turbulence features (intensity and kinetic energy). In conjunction to the experiments, we performed direct numerical simulations (DNS) of the flow generated by an owl in the flapping flight. The wing geometry was extracted from the planform image of the owl wing and a triangulated 3D model was reconstructed. The kinematics were extracted from the trajectories of a set of markers placed along the wing span, which were recorded during the wind tunnel flight. The motion of the markers was transferred to the triangulated surface model by means of an image-registration technique based on the large deformation diffeomorphic metric mapping (LDDMM) framework, allowing alignment of the surface meshes at various phases of the flapping cycle. The derived position and velocity of each point were used as a boundary condition for the computations. The latter were conducted utilizing an immersed boundary (IB) method, which is a cost/efficient approach to conduct DNS with large boundary displacements.
