Correlation of Entrainment and Lift Enhancement for a Two-Dimensional Propulsive Wing 872325
Results from an experimental investigation of a two-dimensional propulsive wing configuration will be presented and correlated. A low-speed wind tunnel model employing a modified NACA 0025 airfoil section, with a propulsive nozzle exhausting over the upper surface of the airfoil at the 70 percent chord position was tested. Test data were obtained for angles of attack of −5, 0, 5, 10 and 15 degrees, and at wind tunnel dynamic pressures of 0,1,5, and 10 lbf/ft2. The propulsive flow was simulated by a compressed air source with nozzle pressure ratios ranging from 1 to 1.10 and simulated jet momentum coefficients from 0 to 2.8.
A significant entrainment of air preceding the nozzle exhaust station was observed that contributes directly to the lift enhancement. The lift coefficient and entrainment velocity increment were found to correlate directly with the propulsive velocity increment. Linear correlations based on momentum pressure parameters employing a “neutral point” concept were also found to provide an excellent correlation of the lift enhancement and entrainment velocity.
Further testing is planned at extended values of nozzle pressure ratio, various height-to-chord ratios of the propulsive nozzle, and with rounded as well as sharp trailing edges. A theoretical analysis of the mixing and entrainment process is also currently underway.