Search

Aerodynamic performance of aircraft wings vary with flight path conditions and depend on efficiency of high lift systems. In this work, a study on high lift devices and mechanisms that aim to increase maximum lift coefficient and reduce drag on commercial aircraft wings is discussed. Typically, such extensions are provided to main airfoil along span wise direction of wing and can increase lift coefficient by more than 100% during operation. Increasing the no of trailing edge flaps in chord wise direction could result in 100% increment in lift coefficient at a given angle of attack but leading edge slats improve lift by delaying the flow separation near stall angle of attack. Different combinations of trailing edge flaps used by Airbus, Boeing and McDonnel Douglas manufacturers are explained along with kinematic mechanisms to deploy them. The surface pressure distribution for 30P30N airfoil is evaluated using 2D vortex panel method and effects of chord wise boundary layer flow transitions on aerodynamic lift generation is discussed. The results showed better agreements with experiment data for high Reynolds number (9 million) flow conditions near stall angle of attack.

Experimental measurements to assess the aeroacoustic capabilities of 30P30N airfoil fitted with two different types of serrated slat cusps were carried out at the aeroacoustic wind tunnel at the University of Bristol. The results from the simultaneous surface pressure measurement within and close to the slat cove region and far-field noise measurements above the slat trailing edge are presented to gain a deeper understanding of the noise generation mechanism of the slat and other presented configurations. The far-field noise measurement results showed that significant noise reduction at the vortex shedding frequency can be achieved by the use of serration-2 and No-Cusp configuration. The coherence results for all the frequencies are almost zero for the No-Cusp configuration and the coherence was notably reduced for the Serration-2 configuration. Further higher-order statistical and spectral analysis showed that even the serration-1 with small serrations reduces the energy within the norrowband peaks to some level.

Experimental measurements were carried out to assess the aeroacoustic characteristics of 30P30N airfoil fitted with two different types of slat cove fillers at the aeroacoustic facility at the University of Bristol. The results are presented for the angle of attack α = 18◦ at a free-stream velocity of U∞ = 30 m/s which corresponds to a chord-based Reynolds number of Rec = 7 × 10◦ . Simultaneous measurements of the unsteady surface pressure were made at several locations in the vicinity of slat cove and at the far-field location to gain a deeper understanding of the slat noise generation mechanism. The results are analyzed using a higher-order statistical approach to determine the nature of the broadband hump seen at low-frequency for the 30P30N high-lift airfoil observed in recent studies and also to further understand the tone generation mechanism within the slat cavity. A series of cross-correlation and coherence of the unsteady pressure measurements are carried out to identify and isolate the low-frequency hump. Wavelet analysis is performed to investigate the nature of the slat-wing resonant intermittent events in both time and frequency domains. The far-field noise measurement results showed that significant noise reduction can be achieved by the use of slat cove fillers. A series of far-field and near-field correlation are also presented to show the propagated noise from the slat.

The results of numerical simulations on a generic high-lift configuration are shown. The high-lift airfoil features a finite slat, where the slat-end creates strong longitudinal vortices interacting with the flow along the suction side. For the simulations, two computational grids with varying density are created. The properties of the grids are presented. The simulations are performed with the DLR TAU-Code at different angles of attack up to stall. The Menter-SST eddy viscosity turbulence model and the JHh-v2 Reynolds-Stress-Model are applied. Two vortices exist at the spanwise end faces of a slat and the corresponding clean-nose, they trail downstream on the suction side of the wing and influence the high-lift behavior of the configuration. A strong interaction between both vortices is observed for higher angles of attack. The behavior of the vortex system and the stall mechanism is characterized. In particular the effect of the turbulence models of different types on the vortex behavior is shown.