Flow over NACA-0009 and Eppler-61 Airfoils at Reynolds Numbers 5000 to 60,000

摘要

The flow about NACA-0009 and Eppler-61 airfoils at (chord-based) Reynolds numbers between 5000 and 60,000 is studied using flow visualizations and incompressible, time-accurate, two-dimensional, laminar Navier-Stokes simulations. Good agreement is found between experimental and numerically simulated flow patterns, as long as the flow remained nonturbulent. The study outlines three phases of angle-of-attack-dependent transition from fully laminar to partly turbulent flow around the airfoils, which are universally applicable at these Reynolds numbers. The first phase is characterized by a laminar wake that appears stable for at least a few chords behind the airfoil; in the second phase, the wake reforms into a well-ordered vortex street; in the third phase, this street becomes unstable and a separation bubble is formed on the suction side of the airfoil. The pattern of the flow changes phases as the angle of attack increases; the exact angles at which the change occurs are airfoil- and Reynolds-number-dependent.