Spanish handheld fans have a discrete skeleton,  comprising a periodic arrangement of retractable beam-like elements, covered by a piece of fabric. This structure is reminiscent of the wings of birds,  where the feather is the repetitive unites,  linked to the body by a central rigid shaft (the Rachid).   Fish fins also show a similar structure,  with spines protruding from the body and recovered by a thin layer of skin.  Fans, wings, and fins all have the same purpose of generating a propulsive flow in the surrounding fluid.  We investigate how flapping flexible foils made of heterogeneous discrete structures interact with the surrounding fluid. We developed a precision experimental apparatus to measure and characterize the airflow through particle image velocimetry.  In parallel, we quantify the forces, torques, and instantaneous deformation of the foil. Our results demonstrate the complementary benefits of heterogeneous flexible foils in simultaneously enhancing the air flux while reducing the required power input during flapping.

Handheld fans: the fluid-structure interaction of flapping foils

The Virtual Technical Meeting of the Society of Engineering Science 2020 is the first fully virtual meeting of the SES community to envision and connect during the hiatus created by Covid-19, providing a platform for the exchange of ideas, and to showcase the latest research in the field of engineering science.

[Visit the Programme](https://drive.google.com/file/d/1BoCPBzrr1IQFANuzQI8a-paXCJoOcCkB/view?usp=sharing) | [Visit the Prerecorded Video/Poster List](https://drive.google.com/file/d/1XHLeEXJxEFjCSsNScuLDfMwy1X7oy7oJ/view?usp=sharing) | [View the Session Grid](https://drive.google.com/file/d/1VeDOC-Ev5m_ymYjXnjaXSZHR3_DARiLt/view?usp=sharing)