Airfoil lift calculation using wind tunnel wall pressures

An experimental method to calculate lift using static pressure ports on the wind tunnel walls and its associated limits has been explored in this article. While the wall-pressure measurement (WPM) technique for lift calculation has been implemented by other researchers, there is a lack of literature on the sensitivity of the WPM method to airfoil chord length, model thickness, surface roughness, and freestream conditions. Chord sensitivity studies showed that the airfoil chord to test section length ratio plays an important role in the accuracy of the measurements. Models need to be appropriately sized for optimum performance of the WPM method. Additionally, choosing the correct scaling ratio also ensures independence of lift measurements from freestream Reynolds number conditions. Finally, a combination of symmetric and cambered airfoils with thicknesses varying from 6% - 21% were tested and successfully validated against reference data for a freestream chord Reynolds number range of 100,000 to 550,000. The WPM method was found to be sensitive to varying surface flow conditions and airfoil thickness and has been shown to be a viable replacement to traditional lift measurement techniques using load balances or airfoils with surface pressure ports.