F. Obermeier, O. Schürmann

Experimental results of a parametric study on two-dimensional blade vortex interaction noise are presented in this paper. Experiments were performed in a transonic wind-tunnel, the airfoil was a NACA 23012 profile. The angle of attack of the airfoil was varied systematically between oo and 1 oo and the miss distance of the vortex between 0 mm and 46 mm. The Mach-number was always M = 0.57. The vortices were produced by a vortex generator ahead of the airfoil, only vortices with a well defined structure were used in the experiments. Results are presented. The absolute density distribution just ahead of the airfoil was measured by means of a Mach-Zehnder interferometer. A sufficient high time solution was made possible by the use of a CranzSchardin camera. The instantaneous pressure distribution at the airfoils surface was recorded by a set of KULITE-transducers mounted in the leading edge region. These simultaneous measurements allow to check the validity whether the pressure can be determined from the density by means of an adiabatic equation of state. The angle of attack turns out to be a very important parameter. An increasing angle leads to a stronger compressibility wave while the transonic wave becomes weaker. This also affects the directional pattern of the emitted sound. For very small miss distance both the compressibility and the transonic waves seem to get weaker. From the surface pressure measurements the sound radiation was calculated by an integral method proposed by Farassat. It indicates - like in the interferometric flow visualization - that the transonic effects are much stronger than the compressible effects. This might be due to the vortex structure obtained by the special vortex generator used in our experiments.

First Joint CEAS/AIAA Aeroacoustics Conference, München, 1995

Conference Paper

englisch

21,0 x 29,7 cm, 8 Seiten

DGLR-Bericht, 1995, 1995-01, First Joint CEAS/AIAA Aeroacoustics Conference - Proceedings; S.357-364; 1995; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aeroacoustics

Bibliothek

1995