# Numerical Simulation of the Advantages of the Figure-Eight Flapping Motion of an Insect on Aerodynamics under Low Reynolds Number Conditions

## TL;DR

This paper studies how insects' figure-eight wing motion improves flight efficiency at low Reynolds numbers, relevant for small drone design.

## Contribution

The study identifies optimal figure-eight wing motion patterns for efficient lift generation at low Reynolds numbers.

## Key findings

- Motion with smaller initial phase of elevation angle (φe0≤90°) generates lift more efficiently across Reynolds numbers.
- Figure-eight motion is more effective at low Reynolds numbers.

## Abstract

In proceeding with the advanced development of small unmanned aerial vehicles (UAVs), which are small flying machines, understanding the flight of insects is important because UAVs that use flight are attracting attention. The figure-eight trajectory of the wing tips is often observed in the flight of insects. In this study, we investigated the more efficient figure-eight motion patterns in generating lift during the hovering motion and the relationship between figure-eight motion and Reynolds number. For this purpose, we compared the ratios of the cycle-averaged lift coefficient to the power coefficient generated from each motion by varying the elevation motion angle, which is the rotational motion that represents the figure-eight motion, and the Reynolds number. The result showed that the motion with a smaller initial phase of the elevation motion angle (φe0≤90°) could generate lift more efficiently at all Reynolds numbers. In addition, the figure-eight motion was more effective when the Reynolds number was low.