Direct Numerical Simulations of Transonic Flow Around an Airfoil at Moderate Reynolds Numbers

摘要

To reduce friction and wave drag on the wings of more-efficient next-generation aircraft, it is important to understand laminar-turbulent boundary-layer transition and shock-wave interactions. In this contribution, fully resolved direct numerical simulations of Dassault Aviation's V2C profile at transonic conditions and a Reynolds number of half a million are presented. Kelvin-Helmholtz instabilities appear in the shear layers on the pressure and suction sides, followed by a self-sustained laminar-turbulent transition process promoted by the stretching of rib vortices between larger corotating structures. Multiple acoustic structures interacting with the boundary layer are also observed, together with upstream-propagating shock waves. Regions of flow separation on the suction side exhibit unsteadiness with Strouhal numbers in the range of St approximate to 0.5-0.6. This is distinct from a standing wave oscillation in lift at St = 0.12. which agrees well with transonic buffet frequencies reported for experiments on the same airfoil at higher Reynolds numbers. The insensitivity of the principal results to the chosen grid resolution and spanwise domain size is carefully established.