Effect of Ground Proximity on Aerodynamic Characteristics of NACA 4412 Airfoil.

Ground effect plays a vital role in modulating the flow behavior over any streamlined body. The most widely used wing-in ground effect (WIG) aircrafts and seaplanes utilize this phenomenon in order to enhance the aerodynamic performance during the landing and take-off phases of flight. This paper investigates the aerodynamics of ground effect on a NACA 4412 rectangular wing without end plates. The experiment was conducted in a low-speed wind tunnel at Re=2×105 for the ground clearance of 1 and 0.5 of the chord, measured from the maximum thickness position on the airfoil. The pressure distribution over the chord length was recorded for α=3° and 6° to verify the effect of ground clearance during takeoffs. The results have shown to be in good accordance with the literature, as the coefficient of lift augmented with increase in ground proximity and the induced drag was minimized.

Features of flow around transport aircraft model with running propellers by modelled engine failure in wind tunnel

This paper presents the experiment results of modelling the one engine failure at the landing mode on a model of a light transport airplane in the T-102 TsAGI low speed wind tunnel. The effect of starboard and port engines failure on the aerodynamic characteristics and stability of the model is researched. The model maximum lift coefficient is reduced about ≈8% and there are the same moments in roll and yaw for starboard and port engines failure case. It was found that the failure of any engine has little impact on the efficiency of control surfaces. Approaches of compensation of forces and moments arising in the engine failure case were investigated.

Improvements of a Hard-Wall Closed Test-Section of a Subsonic Wind Tunnel for Aeroacoustic Testing

For achieving accurate aeroacoustic measurements to the aircraft industry, a low-speed wind tunnel, primarily designed for aerodynamic testing, is modified to provide lower background noise environment. Based on data from single microphone at different wind tunnel locations and microphone phased-array measurements inside the test-section, the main noise sources are identified and feasible alternatives are implemented for reducing the background noise such as new acoustically treated corner-vanes and sidewall lining located upstream the drive system. The acoustically transparent concept for the test-section is also investigated showing promising results for further improvements in the wind tunnel. Results are presented for sound pressure levels from single microphone measurements at different locations in the wind tunnel as well as from the beamforming array inside the test-section. Background noise measurements before and after improvements confirm that the ability of performing aeroacoustic tests has significantly increased with noise reduction of 5 dB inside the test-section.

Verification of a chamberless HLFC design with an outer skin of variable porosity

A chamberless HLFC leading edge segment featuring an outer skin with variable porosity has been designed, manufactured and wind tunnel tested under flight Reynolds-number conditions. The aerodynamic design involved the extention of current HLFC design routines to variable pressure loss characteristics of the outer skin. Advanced options for structural design and manufacturing solutions with focus on industrialization, arising from the avoidance of aerodynamically driven chambering, are explored. The leading edge segment has been installed on an existing vertical tail-plane model and tested at the large low-speed wind-tunnel facility DNW-LLF. The design process and some results of the successful verification of the chamberless design are presented herein.