The quality of airflow generated by fans is essential for users directly exposed to it. We developed a fan inspired by the flapping motion of bird wings to produce natural-like airflow. Our prototype has two vertically oscillating wings that create airflow. Measurements were performed to analyze wind direction, wind velocity distribution, and power spectrum, and compared with those of conventional propeller fans. The power spectrum of airflow generated by flapping wings closely approximates that of natural wind. This approach offers a promising alternative to traditional fan designs, enhancing user comfort and well-being.

It is known that when fish swim in schools, the fish behind can achieve efficient swimming due to the reverse Kármán vortices generated by the fish in front. Theoretical calculations and experimental demonstrations have been conducted on this phenomenon to date. Apart from the tendency of fish to swim in schools, fish in a water flow have a tendency to stay near objects. On the downstream side of an object in a water flow, regions of recirculation (or flow stagnation) occur, and once the water flow exceeds a certain velocity, Kármán vortices are generated downstream. If fish utilize reverse Kármán vortices for efficient swimming, it can be hypothesized that they may also take advantage of the Kármán vortices generated downstream of objects. In this study, we aim to demonstrate this by conducting CFD (Computational Fluid Dynamics) analysis and experiments using a fish robot.