Aeroacoustic Investigation of a Single Airfoil Tip Leakage Flow

Abstract

Combined near and far field aeroacoustic measurements have been carried out during an original laboratory scale low Mach number (0-0.3) experiment about the tip leakage flow past a single non-rotating airfoil. Such measurements were made possible by the use of a single airfoil located in the potential core of an open jet flow in the anechoic wind tunnel of the Ecole Centrale de Lyon. The airfoil was mounted between two flat plates. A strong tip clearance flow was achieved without rotation by paying a special attention to the choice of the airfoil which was a 5% camber, 10% thickness NACA5510 airfoil that provided a high lift at a 15°angle of attack. The experiment gave rise to an extensive data set obtained with several flow velocity measurement techniques (HWA, LDA, PIV), steady and unsteady pressure measurements on the airfoil and the casing plate as well as far field pressure measurements. Further, cross-analyses of various velocity and pressure signals allowed to locating sources and identifying their mechanisms. Results showed evidence of two components of tip leakage broadband self noise.

Time-resolved PIV measurements of a tip leakage flow

“…As a result, the angle of attack was set to 16:5 AE 0:5 , that is significantly higher than in the former experiment (15 AE 0:5 Þ. The C p at mid-span shown in Figure 4 fits within 7% the C p reported in Jacob et al 1 LDV measurements in the tip region out in the same region as PIV measurements, namely around the airfoil in the gap region. They provide a useful comparison for the PIV measurements as well as spectral information.…”

“…than 2:5%. This was not the case in Jacob et al, 1 where the interaction source was probably responsible for a large part of the background noise resulting in a very low signal-to-noise ratio for the tip clearance noise.…”

“…The pressure distribution at mid-span helps to determine the angle of attack in order to meet similar airfoil loading conditions as those reported in Jacob et al 1 These are highly dependent Table 1. Boundary layer thickness , displacement thickness à , momentum thickness and shape factor H at four streamwise positions in the incoming flow.…”

Calculation of sound power level of tandem axial fan

“…Many theoretical and experimental works deal with the understanding of the noise formation mechanism in turbomachine elements. In [3], the obtained results allow understanding the nature of acoustic radiation sources in the flow past an isolated fixed profile. Experiments were carried out in the Mach number range of M=0...0.3.…”

Measurement and analysis of radiated sound from a low speed fan with a large tip gap

“…Many successful studies of tip vortex noise have been performed in the inertial frame as it allows for the easiest reduction of competing noise sources (Brooks and Marcolini, 1986;Brooks et al, 1989;Grilliat et al, 2007;Grilliat et al, 2008;Jacob et al, 2010). In each of these cases, it was found to have a comparatively weak contribution to the overall spectrum.…”