Separation control on airfoil and wing with finite boundary layer trips

The influence of boundary layer trips of various aspect ratios on aerodynamic performance and flow development over a NACA 0018 airfoil and wing is investigated experimentally. Direct force and particle image velocimetry measurements are performed at a chord Reynolds number of 60000 and an angle of attack of 5 degree. The effect of trip length relative to the model span is considered over a range of trip aspect ratios from 0.08 to 1 relative to the model span, with all trips centred at the midspan plane of the models. The baseline stalled flow development is shown to be augmented significantly for all the cases examined, producing substantial changes to aerodynamic performance. The results demonstrate that trip segments affect the flow over a significantly wider spanwise regions compared to the size of the trip. While the trip spanwise extent is shown to have a prominent influence on the overall flow development, comparable gains in aerodynamic performance can be achieved over a relatively wide range of trip aspect ratios.