An experimental study of the flow-induced noise created by a wall-mounted finite length airfoil

AIAA 2014-3290This paper presents the results of an experimental investigation of the sound produced by flow interaction with a wall-mounted finite length airfoil at low-to-moderate Reynolds number. Acoustic measurements have been taken in an anechoic wind tunnel at a range of Reynolds numbers, angles of attack and for a variety of airfoil aspect ratios (airfoil length to chord ratio) with a single microphone and two perpendicular planar microphone arrays. For comparison, measurements have also been taken with a semi-infinite or two- dimensional airfoil and a half-span airfoil with tip flow but no boundary layer impingement. The experimental data is used to examine changes in wall-mounted finite airfoil noise production as a function of Reynolds number, angle of attack and airfoil aspect ratio. Additionally, the data gives insight into the airfoil noise generation mechanisms and the influence of flow at the airfoil tip and wall junction on noise productionDanielle J. Moreau , Zebb Prime and Con J. Doola

Experimental Study on Noise Reduction through Trailing-Edge Brushes

Within an experimental trailing-edge noise reduction study in the Aeroacoustic Wind Tunnel Braunschweig (AWB) both acoustic and aerodynamic effects of trailing-edge brush-devices were examined. Directional microphone and hot-wire measurements were undertaken on a zero-lift generic plate model (Re = 2.1 to 7.9 x 106). Various brush concepts were tested to clarify the functional relationship between design parameters and the ensuing aeroacoustic properties. First results of this ongoing work indicate a significant source noise reduction in excess of 10 dB, thereby revealing two relevant noise reduction mechanisms. In addition to broadband turbulent boundary-layer trailing-edge noise also narrow band contributions due to vortex shedding from the edge were alleviated

Unsteady surface pressure measurements on trailing edge serrations based on digital MEMS microphones

The physics of turbulent flow reaching the airfoil trailing edge is fundamental to the understanding of the Turbulent Boundary Layer (TBL) noise production mechanism. The experimental validation of semi-empirical and computational models requires advances in current experimental techniques and instrumentation to allow accurate determination of turbulent structures. This research investigates the applications of digital MEMS microphones embedded for the experimental determination of unsteady wall pressure in a 3D printed NACA0012 airfoil at chord-based Reynolds number 200,000<Re<700,000. The development of this experimental technique brings challenges regarding the construction since sensors and components must be miniaturized in order to maximize the sensor spatial resolution. This paper discusses the implementation of this novel wall pressure transducer. Results indicate that the proposed approach can be effectively applied to the experimental determination of near-wall turbulence structures and other flow features, which is a major step toward improved TBL noise prediction

Three-Dimensional Computation of Bubbles Near a Free Surface

10.1006/jcph.1998.6042Journal of Computational Physics1461105-123JCTP