<p>With conventional flow visualization/measurement techniques and methods, it is challenging and difficult to study&nbsp;the&nbsp;complex unsteady/3D flow around&nbsp;flying insects. In the absence of a clear understanding about the complex flow in the complete spatial and temporal domain, the aerodynamic mechanisms&nbsp;and flow physics about the flying insects are not fully understood and new flow physics or mechanisms may be overlooked. Therefore, to reveal the full flow field around flying insects, novel experimental methods and techniques are highly desired.</p><p>In this study, two newly introduced methods of flow visualization and measurement on flying insects are implemented to investigate the complex flow around flying houseflies. The high-speed schlieren photography is implemented on tethered and free flying houseflies inside a clear container which has a stable vertical temperature gradient established inside. The container is heated from the top and cooled from the bottom to create a density/refraction index gradient inside. When insects flap their wings and disturb the flow, the density/refraction index field deforms accordingly, which is visualized through a high speed schlieren photography. Moreover, a physics based optical flow method is implemented on the derived schlieren images to quantify the averaged velocity field. On the other hand, the Shake-the-Box (Particle Tracking Velocimetry) system is implemented on tethered houseflies with a flow measurement volume of 30 mm×30 mm×6 mm, which covered the most region of the wake. The Shake-the-Box system successfully captured the detailed 3D flow field in the wake of the insects that is analyzed and compared with the results derived from the schlieren photography experiments.</p>

Volumetric Flow Visualization and Measurement on Housefly Using High Speed Schlieren Photography and Shake-the-Box System

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

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