Regular Article

Mode and regime identification for a static NACA0012 airfoil at transitional Reynolds numbers

Department of Mechanical and Aerospace Engineering Royal Military College of Canada Kingston, Ontario K7K 7B4, Canada

^* e-mail: benaissa-a@rmc.ca

Received: 21 February 2020
Accepted: 25 November 2020

Abstract

This work examines the flow structure modes in the boundary layer and in the wake of a NACA0012 airfoil in static conditions at transitional chord-based Reynolds numbers (Re_c), for small angles of attack (α). A laminar mode, with a laminar separation of the boundary layer and laminar Kármán streets in the wake, was first observed for Re_c < 61400 and α = 0°. For 77 000 < Re_c < 118600, which corresponds to a regime between laminar and transitional mode called subcritical mode, the boundary layer exhibited a long separation bubble reattached close to the trailing edge, and the wake showed a turbulent Kármán street. Finally, for higher Re_c and α, a critical transition mode consisted of a long bubble followed by a turbulent separation, and a less structured vortex street in the wake of the airfoil.