Experimentalresults are presented for the aerodynamics and acoustics of an unswept wing with a half-span flap and a full-span slat. Concurrent aerodynamic and acoustic measurements were obtained for high-lift riggings representative of landing-approach configurations.Phased microphone array measurements indicate that slat gap noise is most significant for high slat deflections where the slat is lightly loaded. More specifically, the peak noise level for the 25deg slat deflection was 20 dB higher than that of the 9-deg slat deflection. Measurements of intermediate angles indicate a gradual decrease in slat noise as slat deflection is decreased. Strouhal frequency scaling of the 25deg slat configuration suggests that vortex shedding from the slat trailing edge may be an important noise mechanism. However, a non-linear relationship between slat noise level and angle of attack suggests a more complex phenomenon. Computational results detail the strength of the shear layers in the slatcove flow field. Variations in the slat-cove shear layers with slat deflection and angle of attack are presented. From correlations between the computed results and the measured acoustics, it is hypothesized that a KelvinHelmholtz instability develops in the slat cove and a feedback mechanism forms between the slat-cove and slat trailing-edge flow fields. Nomenb 6 wing span wing chord section lift coefficient = P / qc CL total lift coefficient = L / qS CP pressure coefficient = (p -pm) / q d distance from dividing streamline e section lift L total lift LP sound pressure level, dB re 20 pPa

Experimental measurements of surface pressure distributions and wake profiles were obtained for an NACA 4412 airfoil to determine the lift, drag, and pitching-moment coefficients for various configurations. The addition of a Gurney flap increased the maximum lift coefficient from 1.49 up to 1.96, and decreased the drag near the maximum lift condition. There was, however, a drag increment at low-to-moderate lift coefficients. Additional nose-down pitching moment was also generated by increasing the Gurney flap height. Good correlation was observed between the experiment and Navier-Stokes computations of the airfoil with a Gurney flap. Two deploy able configurations were also tested with the hinge line forward of the trailing edge by one and 1.5 flap heights, respectively. These configurations provided performance comparable to that of the Gurney flap. The application of vortex generators to the baseline airfoil delayed boundary-layer separation and yielded an increase in the maximum lift coefficient of 0.34. In addition, there was a significant drag penalty associated with the vortex generators, which suggests that they should be placed where they will be concealed during cruise. The two devices were also shown to work well in concert.

Experimental measurements of surface pressure distributions and wake profiles were obtained for an NACA 4412 airfoil to determine the lift, drag, and pitching-moment coefficients for various configurations. The addition of a Gurney flap increased the maximum lift coefficient from 1.49 up to 1.96, and decreased the drag near the maximum lift condition. There was, however, a drag increment at low-to-moderate lift coefficients. Additional nose-down pitching moment was also generated by increasing the Gurney flap height. Good correlation was observed between the experiment and Navier-Stokes computations of the airfoil with a Gurney flap. Two deploy able configurations were also tested with the hinge line forward of the trailing edge by one and 1.5 flap heights, respectively. These configurations provided performance comparable to that of the Gurney flap. The application of vortex generators to the baseline airfoil delayed boundary-layer separation and yielded an increase in the maximum lift coefficient of 0.34. In addition, there was a significant drag penalty associated with the vortex generators, which suggests that they should be placed where they will be concealed during cruise. The two devices were also shown to work well in concert.

No abstract

Airframe noise generated by commercial aircraft at landing approach is a barrier to the achievement of desired noise reduction goals for the next generation of aircraft.