Experimental Investigation of Generation Mechanism of Aerodynamic Noise. 1st Report. On a Coherent Structure of Surface Pressure Fluctuation on a Circular Cylinder.

明由, 飯田; 肇, 藤田; 千幸, 加藤; 靖, 高野

doi:10.1299/kikaib.61.4371

Cited by 9 publications

(3 citation statements)

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“…Since it is considered that the aerodynamic sound highly depends on the flow structures, it is very important to investigate them. It is reported that the correlation length of a large scale vortex in the spanwise direction, which is one of factors in evaluating a scale of the flow structure, plays an important role for analyzing the aerodynamic noise (Iida, et al, 1995, Kato, et al, 1994. Moreover, Shirakashi et al (1986) have experimentally investigated the structure of Karman's vortex shedding from a yawed cylinder in a uniform flow, and reported that a secondary flows along the axis of the cylinder lead to the reductions in the frequency and the regularity of the vortex shedding as the inclined angle increases.…”

Section: Introductionmentioning

confidence: 99%

Visualization of three-dimensional flow structures in the wake of an inclined circular cylinder

Matsuzaki

Shingai

Haramoto

et al. 2004

J Vis

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In the previous measurements of the aerodynamic sound generated from an inclined circular cylinder, it is reported that the sound pressure level (SPL) changes with the aspect ratio and the inclined angle. Therefore, we have investigated the changes in the vortex structure of the wake considered as one of the causes of the SPL variation. Using the low-noise wind tunnel, the velocity fluctuation in the wake is measured to obtain the correlation length. Moreover, the flow visualization is performed with a hydrogen bubble method and a numerical analysis method in order to clarify how the wake structure changes by variations of aspect ratio and inclined angle. As a result of this investigation, it is shown that the spanwise structure of Karman's vortex is highly influenced by the interference of Karman's vortex with the bottom endplate, and that the influence on the spanwise structure in the wake becomes greater as the aspect ratio decreases and the inclined angle increases.

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Section: Introductionmentioning

confidence: 99%

Visualization of three-dimensional flow structures in the wake of an inclined circular cylinder

Matsuzaki

Shingai

Haramoto

et al. 2004

J Vis

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“…at ~ =20 ° is smaller than one at ~u--0 °. (1)(2)(3) In the case of A=10, the compensated Strouhal number at ~ = 20 ° is smaller than one at ~u =0O, particularly near the bottom of the cylinder.…”

Section: Discussionmentioning

confidence: 92%

Relation between the three-dimensional flow structure and aerodynamic sound generated from inclined circular cylinder

et al. 2004

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The major causes of the sound pressure level (SPL) variation due to the changes of the inclined angle of a circular cylinder and the aspect ratio (ratio of distance between endplates to cylinder diameter) were investigated. The velocity fluctuation of the wake and the surface pressure fluctuati6n of the cylinder were measured in a low noise wind tunnel to fred the correlation length, coherent output power and Strouhal number. The results show that the changes of these values qualitatively correspond with the change of SPL. Flow visualization tests are performed to clarify the variation of wake in relation with inclined angle and aspect ratio. It is found that the spanwise structure of Karman's vortex street is broken down by the upward flows generated around the bottom endplate, and the degree of the interference between the upward flow and Karman's vortex street is smaller when the aspect ratio is larger.

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“…Some reports were presented for the inclined cylinder to make clear the effects of the three-dimensional characteristics to the wake vortex [7][8][9][10] . It was pointed out that the flow turned to the direction normal to the circular cylinder.…”

Section: Introductionmentioning

confidence: 99%

Relationship between Aeolian tone and Wake Vortex from Inclined Flat Blade (Characteristics of Vortex Shedding in Spanwise Direction)

Yoshitake

Hayashi

Sasaki

et al. 2009

JFST

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The three dimensional structure of the wake vortex was investigated in relating to the aeolian tone from the inclined blade. It was pointed out that the aeolian tone is largest not at zero, but at ten degree of the inclined angle. The correlation length of the wake vortex in span becomes large at small inclined angles. The large scale structures of the wake vortex are generated in zero and ten degree of inclined angle. The shape of the structure is influenced with the span-wise velocity in the dead air region. There are small scale spots of the pressure fluctuation at the trailing edge. The spots are interacted each other and make a large cluster of the pressure fluctuation. It is proposed that the scale of it is decided by the timing of the wake vortex formation. And the shape of the wake vortex structure is closely related with the scale of it. The correlation length of the wake vortex is calculated from the shape of the structure. The estimation of aeolian tone by using the length with Fukano's model is well coincided to experiments.

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Experimental Investigation of Generation Mechanism of Aerodynamic Noise. 1st Report. On a Coherent Structure of Surface Pressure Fluctuation on a Circular Cylinder.

Cited by 9 publications

References 0 publications

Visualization of three-dimensional flow structures in the wake of an inclined circular cylinder

Visualization of three-dimensional flow structures in the wake of an inclined circular cylinder

Relation between the three-dimensional flow structure and aerodynamic sound generated from inclined circular cylinder

Relationship between Aeolian tone and Wake Vortex from Inclined Flat Blade (Characteristics of Vortex Shedding in Spanwise Direction)

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