# Numerical Study into the Spanwise Effects for the Three-Dimensional Unsteady Flow over a Bio-Inspired Corrugated Infinite Wing at Low Reynolds Number

## TL;DR

This study explores how corrugated wings, inspired by insects, behave aerodynamically at low speeds, revealing how their 3D flow patterns change with speed and angle.

## Contribution

The study extends flow regime classification for corrugated wings and highlights limitations of 2D assumptions in low Reynolds number aerodynamics.

## Key findings

- At low Reynolds numbers, flow remains steady and two-dimensional with localized recirculation.
- Higher Reynolds numbers or angles of attack induce periodic vortex shedding and three-dimensional flow structures.
- Root corrugation delays flow separation in transitional regimes but does not improve lift-to-drag ratios.

## Abstract

Corrugated insect wings inspire biomimetic aerodynamic design, yet their behaviour at low and transitional Reynolds numbers remains not fully understood. This study presents a three-dimensional computational analysis of flow over an infinite corrugated wing across Reynolds numbers from 10 to 10,000 and angles of attack from −5 to 20°, with emphasis on spanwise effects. An expanded verification and validation procedure ensured numerical reliability. At the lowest Reynolds numbers, the flow is steady and largely two-dimensional, with localised recirculation zones. As Reynolds numbers or angles of attack increase, the flow transitions to periodic vortex shedding, and three-dimensional structures appear. At a Reynolds number of ten thousand, periodic shedding occurs at zero degrees incidence, indicating a shift toward turbulent or bluff body-like behaviour. The examined corrugated profile does not exhibit a lift-to-drag benefit over smooth aerofoils in steady gliding, although root section corrugation helps delay separation in transitional regimes. This behaviour reflects mechanisms used by dragonflies to maintain stable gliding despite textured wings. By extending flow regime classification, the study identifies conditions where two-dimensional assumptions fail and highlights the influence of spanwise flow structures. These findings deepen understanding of insect wing aerodynamics and support biomimetic design of future wings.