# Assessment of turbulent boundary layers on a NACA4412 wing section at moderate Re

## TL;DR

This study uses DNS to analyze turbulent boundary layers on a NACA4412 wing at moderate Reynolds number, revealing effects of adverse pressure gradients on flow structure, turbulence, and energy distribution.

## Contribution

First detailed DNS analysis of turbulent boundary layers on a NACA4412 wing at Re=400,000, highlighting APG effects on turbulence and flow structures.

## Key findings

- APG causes a more prominent wake and steeper logarithmic region.
- Development of outer velocity fluctuation peaks under APG.
- Enhanced turbulence production and energy in large-scale motions.

## Abstract

The results of a DNS of the flow around a wing section represented by a NACA4412 profile, with Rec = 400, 000 and 5 degree angle of attack, are presented in this study. The high-order spectral element code Nek5000 was used for the computations. The Clauser pressure-gradient parameter ? ranges from 0 and 85 on the suction side, and the maximum Re_theta and Re_tau values are around 2,800 and 373, respectively. Comparisons between the suction side with ZPG TBL data show a more prominent wake, a steeper logarithmic region and lower velocities in the buffer region. The APG also leads to a progressively increasing value of the inner peak in the tangential velocity fluctuations, as well as the development of an outer peak, which is also observed in the other components of the Reynolds stress tensor. Other effects of strong APGs are increased production and dissipation profiles across the boundary layer, together with enhanced viscous diffusion and velocity-pressure-gradient correlation values near the wall. All these effects are connected to the fact that the large-scale motions of the flow become energized due to the APG, as apparent from spanwise premultiplied power spectral density plots.