Experimental study on flow and noise characteristics of NACA0018 airfoil

The purpose of this paper is to propose a sound localization method as an alternative of the time-resolved particle image velocimetry (PIV) system for detecting the aerodynamic sound source of a circular cylinder in a uniform flow. The sound source intensity of a circular cylinder in a uniform flow is evaluated by measuring the time-derivative of instantaneous velocity field in the flow field using a pair of planar PIV system. It allows the visualization of the sound source intensity distribution, which is the time-derivative of the vector product of vorticity and velocity. The experimental results indicate that the aerodynamic sound is generated from the separation point and the velocity fluctuation in the separating shear layer from the circular cylinder. These results agree qualitatively with the previous findings from experiment and numerical simulation, which supports the validity of the present experimental method for evaluating the sound source intensity distribution.

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“…Note that the mean velocity in the test section was uniform within an accuracy of ±1%, and the free-stream turbulence level was about 1% [14].…”

Section: Experimental Apparatusmentioning

confidence: 99%

Measurement of Aerodynamic Sound Source around a Circular Cylinder by Particle Image Velocimetry

Oguma

Yamagata²,

Fujisawa³

2014

JFCMV

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“…1(a)) indicates that the stagnation pressure appears near the lower side of the leading edge of the airfoil, while the low pressure region prevails over the suction side of the airfoil and the pressure increases gradually along the airfoil surface downstream. In order to confirm the validity of the mean pressure coefficient Cpw on the airfoil surface, the present measurement is compared with that of the direct pressure measurement by Nakano et al (2007), which is shown in Fig. 1(b).…”

Section: Resultsmentioning

confidence: 93%

Measurement of pressure field around a NACA0018 airfoil from PIV velocity data

Fujisawa

Oguma

2008

J Vis

Self Cite

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“…They compared the flow pattern with the schematic of natural transition introduced by White (White, 1991) and rearranged the figure to adapt the schematic to separated flow transition ( Figure 5 and 6). (Lock, 2007) Laminar separation bubble may cause adverse effects, such as decreasing of lift force, increasing of drag force, reducing stability of the aircraft, vibration, and noise (Nakano et al, 2007;Ricci et al, 2005;2007;Zhang et al, 2008). Characteristics of LSB must be understood well to design control system to eliminate to LSB or design new aerofoils which do not affect from adverse effects of LSBs.…”

Section: Separated Flow Transitionmentioning

confidence: 99%