# Unsteady aerodynamic effects in small-amplitude pitch oscillations of an airfoil

## TL;DR

This study uses high-fidelity simulations to explore how small-amplitude pitch oscillations affect the unsteady aerodynamics of an airfoil, revealing complex flow behaviors influenced by laminar separation bubbles and transition points.

## Contribution

It provides new insights into the flow physics of oscillating airfoils in sensitive regions, highlighting the impact of laminar separation bubbles on unsteady aerodynamics.

## Key findings

- Large variations in transition points during pitch cycle
- Dynamic changes in laminar separation bubble stability
- Abrupt transition location shifts affecting flow response

## Abstract

High-fidelity wall-resolved large-eddy simulations (LES) are utilized to investigate the flow-physics of small-amplitude pitch oscillations of an airfoil at Re = 100,000. The investigation of the unsteady phenomenon is done in the context of natural laminar flow airfoils, which can display sensitive dependence of the aerodynamic forces on the angle of attack in certain "off-design" conditions. The dynamic range of the pitch oscillations is chosen to be in this sensitive region. Large variations of the transition point on the suction-side of the airfoil are observed throughout the pitch cycle resulting in a dynamically rich flow response. Changes in the stability characteristics of a leading-edge laminar separation bubble has a dominating influence on the boundary layer dynamics and causes an abrupt change in the transition location over the airfoil. The LES procedure is based on a relaxation-term which models the dissipation of the smallest unresolved scales. The validation of the procedure is provided for channel flows and for a stationary wing at Re = 400,000.