An experimental study on aerodynamic sound generated from wake interaction of circular cylinder and airfoil with attack angle in tandem

Munekata, Mizue; Koshiishi, Ryuta; Yoshikawa, Hiroyuki; Ohba, Hideki

doi:10.1007/s11630-008-0212-9

Cited by 13 publications

(6 citation statements)

References 11 publications

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“…They observed the fluids resonant oscillations when the interval is varied. Munekata et al (2008) further investigated the effects of the attack angle of the airfoil located downstream on the characteristics of the aerodynamic sound and wake structure at a given interval between the cylinder and the airfoil. It was found that the SPL decreases with increasing attack angle of the airfoil because of the diffusive wake structure caused by the blocking effect of the airfoil.…”

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confidence: 99%

Numerical investigation on body-wake flow interaction over rod–airfoil configuration

et al. 2015

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Numerical investigations of body-wake interactions were carried out by simulating the flow over a rod-airfoil configuration using high-order implicit large eddy simulation (HILES) for the incoming velocity U ∞ = 72 m s −1 and a Reynolds number based on the airfoil chord 4.8 × 10 5 . The flow over five different rod-airfoil configurations with different distances of L/d = 2, 4, 6, 8 and 10, respectively, were calculated for the analysis of body-wake interaction phenomena. Various fundamental mechanisms dictating the intricate flow phenomena including force varying regulation, flow structures and flow patterns in the interaction region, turbulent fluctuations and their suppression, noise radiation and fluid resonant oscillation, have been studied systematically. Due to the airfoil downstream, a relatively higher base pressure is exerted on the surface of the cylinder upstream, and the pressure fluctuation on the surface of the rod-airfoil configuration with L/d = 2 is significantly suppressed, resulting in a reduction of the fluctuating lift. Following the distance between the cylinder and airfoil strongly decreases, Kármán-street shedding is suppressed due to the blocking effect. The flow in this interaction region has two opposite tendencies: the influence of the airfoil on the steady flow is to accelerate it and the counter-rotating vortices connecting with the leading edge of the airfoil tend to slow the flow down. There may be two flow patterns associated with the interference region, i.e. the Kármán-street suppressing mode and the Kármán-street shedding mode. The primary vortex shedding behind the cylinder upstream, and the shedding wake impingement onto the airfoil downstream, play a dominant role in the production of turbulent fluctuations. When primary vortex shedding is suppressed, the intensity of impingement is weakened, resulting in a significant suppression of the turbulent fluctuations. Due to these factors, a special broadband noise without a manifestly distinguishable peak is radiated by the rod-airfoil configuration with L/d = 2. The fluid resonant oscillation within the flow interaction between the turbulent wake and the bodies was further investigated by adopting a feedback model, which confirmed that the effect of fluid resonant oscillation becomes stronger when L/d = 6 and 10.The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to the body-wake interaction.

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confidence: 99%

Numerical investigation on body-wake flow interaction over rod–airfoil configuration

et al. 2015

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“…They varied the spacing between the rod and the airfoil, such as L/d =2, 4, 6, 8, and 10. They showed that when the spacing is small (L/d = 2), the vortex shedding of the rod upstream, the pressure fluctuation, and the noise radiation are suppressed as shown by Munekata et al [10][11] and when the spacing is large (L/d = 6, 10), the pressure fluctuation, the noise radiation, and the fluid resonant oscillation due to the feedback loop between the rod and the airfoil become stronger.…”

Section: Introductionmentioning

confidence: 94%

“…In this model, a rod is immersed upstream of the blade or airfoil, the wake formed behind the rod interacts with the leading edge of the blade or airfoil. Many studies concerned with the rodairfoil model have been done both experimentally and numerically [9][10][11][12][13][14][15][16][17][18][19][20][21]. Jacob et al [9] measured the flow field of the rod-NACA0012 airfoil model at the fixed spacing between the rod and the airfoil with varying the inflow velocity, and also measured the far field radiated noise spectra that are generated mainly by the bodywake interaction.…”

Section: Introductionmentioning

confidence: 99%

“…They also performed numerical calculations using the Reynoldsaveraged Navier-Stokes (RANS) and the large eddy simulation (LES) approaches and compared numerical results with the measured data. Munekata et al [10][11] measured the flow field of the rod-airfoil model to research the effects of the spacing between the rod (cylinder) and the airfoil and the characteristics of the flow-induced sound generated by the flow around rod-airfoil. They showed that the roll up of the shear layer separated from the upstream rod is suppressed when the spacing between the rod and the airfoil is small, and the interaction between the wake from the rod upstream and the airfoil downstream becomes weak and it results in decreasing the level of the noise radiation.…”

Section: Introductionmentioning

confidence: 99%

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Wake-Body Interaction Noise Simulated by the Coupling Method Using CFD and BEM

Mori¹

2020

Vortex Dynamics Theories and Applications

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In many engineering applications, obstacles often appear in the wake of obstacles. Vortices shed from an upstream obstacle interact with downstream obstacle and generate noise, for example blades in a turbomachinery, tubes in a heat exchanger, rotating blades like a helicopter and wind turbine and so on. This phenomenon is called wake-body interaction or body-vortex interaction (BVI). The rod-airfoil and airfoil-airfoil configurations are typical models for the wake-body interaction. A rod and an airfoil are immersed upstream of the airfoil. In this chapter, we review the noise mechanism generated by the wake-body interaction and show the numerical results obtained by the coupling method using commercial CFD and acoustic BEM codes. The results show that depending on the spacing between the rod or airfoil and the airfoil, the flow patterns and noise radiation vary. With small spacing, the vortex shedding from the upstream obstacle is suppressed and it results in the suppression of the sound generation. With large spacing, the shear layer or the vortices shed from the upstream obstacle impinge on the downstream obstacle and it results in the large sound generation. The dominant peak frequency of the generated sound varies with increase in the spacing between the two obstacles.

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“…It was found that the periodicity of shedding vortices was consistent with the frequency of noise generation. In 2008, Munekata et al [32] studied the influence of airfoil-cylinder interference on aerodynamic noise of the airfoil shedding vortex by an experimental method. The influence of pressure fluctuation on the sound pressure level of the airfoil surface was obtained through the flow visualization and detection experiments of sound source.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Analysis of the Effect of a New Lightning Protection System on Lightning Protection and Aerodynamic Noise Performance of Wind Turbine Blades

Guo

Chen

et al. 2019

Electronics

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In order to tackle the problem of the high failure rate of blades of large wind turbine units due to lightning damage, a new lightning protection system (NLPS) for wind turbine blades is proposed based on the lightning damage mechanism of blades. Firstly, 10 high-voltage discharge tests are performed for blades with and without the NLPS to study the effect of lightning protection. The results show that when the surface of the blade without the NLPS is struck by lightning 10 times, the damage rate of the blade is 100%; for the blade with the NLPS and the lightning attachment position is always on the NLPS in 10 discharge tests, the damage rate of blades is 0% and the lightning protection rate of blades is 100%, indicating that the lightning protection effect for blades with the NLPS is greatly improved. Moreover, the static electric fields of the blades with and without the NLPS are calculated. The results show that the NLPS can shield the electric field around the lower lead wire of the blade, thus effectively reducing the electric field intensity. The NLPS initiates the upward leader more easily than the lower lead wire; therefore, the lightning attachment point is located on the NLPS, thus protecting the blade. Secondly, the aerodynamic and aero-noise characteristics of the blade with and without the NLPS are calculated. The results indicate that the NLPS has little influence on the aerodynamic performance of the blade but has some influence on the aero-noise of the blade. The aero-noise of the airfoil can be reduced at angles of attack of 4°, 8°, 11°, and 15°, but the influence of different phase angles of the airfoil on the amplitude of the sound pressure level (SPL) varies. The aero-noise of the airfoil with the NLPS decreases by 16% and 8% at angles of attack of 4° and 8°, respectively. In general, the design of the NLPS reaches the desired requirements, but it still needs to be further optimized in combination with the blade manufacturing process.

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An experimental study on aerodynamic sound generated from wake interaction of circular cylinder and airfoil with attack angle in tandem

Cited by 13 publications

References 11 publications

Numerical investigation on body-wake flow interaction over rod–airfoil configuration

Numerical investigation on body-wake flow interaction over rod–airfoil configuration

Wake-Body Interaction Noise Simulated by the Coupling Method Using CFD and BEM

Experimental and Numerical Analysis of the Effect of a New Lightning Protection System on Lightning Protection and Aerodynamic Noise Performance of Wind Turbine Blades

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