# History effects for cambered and symmetric wing profiles

## TL;DR

This study uses large-eddy simulations to analyze how adverse pressure gradients affect turbulent boundary layers on different wing profiles, revealing increased turbulence and altered large-scale structures.

## Contribution

It provides detailed insights into the effects of adverse pressure gradients on turbulent boundary layers for cambered and symmetric wings using LES.

## Key findings

- APG increases turbulent kinetic energy, especially in the outer layer.
- Strong APG causes larger velocity fluctuations throughout the boundary layer.
- APG significantly impacts the largest scales in the boundary layer.

## Abstract

The characteristics of complex turbulent boundary layers under adverse pressure gradients are assessed through well-resolved large-eddy simulations (LES) with the spectral-element code Nek5000. Two wing sections are analysed: a NACA0012 at 0 degree angle of attack which presents a mild adverse-pressure gradient (APG) along the chord and a NACA4412 at 5 degree angle of attack with a strong adverse pressure gradient on the suction side, both profiles at Rec = 400,000. The turbulent statistics show that the mild-APG turbulent boundary layer (TBL) of the NACA0012 presents a slight deviation of the velocity fluctuations in the outer region while the strong-APG TBL of the NACA4412 shows significantly larger fluctuations throughout the wall-normal direction with respect to the zero-pressure-gradient (ZPG) TBL. These differences are more substantial in the outer region of the boundary layer. Spectral analyses show that the APG has a significant impact on the largest scales in the boundary layer. Our results indicate that the APG increases the turbulent kinetic energy (TKE) of the TBL, more prominently in the outer layer, and suggest a different mechanism than the one related to high Re in ZPGs.