On the Low Frequency Pressure Fluctuation in a 3/4 Open Jet Automotive
                        Wind Tunnel

Jia, Qingxuan; Zhu, Yunqing; Bao, Di; Rashidi, Mohammad Mehdi; Yang, Zhi

doi:10.29252/jafm.12.05.29530

Cited by 7 publications

(9 citation statements)

References 15 publications

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“…The results show that these deflectors can effectively reduce the air separation in pipe and increase the flow field uniformity in the test section. Jia Q used LES to simulate the vortex structure in the jet shear layer at the nozzle when the low-frequency pressure fluctuation occurs, which is in good agreement with the particle image velocimetry test results 27 . The above simulation methods can provide some reference for the numerical simulation study of pulsation phenomenon in this study.…”

Section: Introductionsupporting

confidence: 54%

The low frequency pressure pulsation and control of the open-jet wind tunnel

Luo

Leng

et al. 2022

Sci Rep

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An open jet wind tunnel has low-frequency pressure pulsation in common wind speed range due to its unique structural form, which seriously damages the quality of flow field in the test section. The low-frequency pressure fluctuation performance and control mechanism of Jilin University open jet and return flow wind tunnel are investigated by experiments and numerical simulation. The results show that the low-frequency pressure fluctuation is a narrow pulse phenomenon that only occurs in certain intervals, and several velocity intervals may be found in the same wind tunnel. The reliability of the numerical simulation is verified by comparing the peak frequency and amplitude of pressure fluctuation in numerical simulation and wind tunnel tests. A simplified model similar to and amplifying the phenomenon is established. The flow structure and vortex evolution are analyzed via detached eddy simulation. In the test section, large-scale shedding vortices are formed at the nozzle exit, introducing periodic pulsating instantaneous velocity and acting with the collector to form an edge-feedback. This acoustic feedback forms resonance with the pipeline circuit, resulting in poor flow field quality. In accordance with the mechanism of nozzle jet, two methods of controlling pulsation are proposed: spoiler and flow-follow device. The study shows that the effects of two methods are abrupt, and the frequency of pressure pulsation is changed. The spoiler destroys the complete structure of vortex ring in free jet and develops into a complementary double vortex ring structure, which is highly sensitive to size factors. The flow-follow device supplements the velocity loss of the free jet at the nozzle and develops into a double vortex ring with master–slave structure in the middle of the test section. Its vibration reduction effect is greatly affected by the flow velocity. It takes effect in an appropriate range where the flow velocity is higher than the nozzle velocity. If the follow velocity is extremely low, the flow-follow device cannot change the original jet structure. If the follow velocity is extremely high, the momentum of the fan will be greatly reduced, the flow field will be unstable, and another order of pulsation may be induced. This work lays a solid foundation for further understanding the aerodynamic characteristics and optimization mechanism of open jet wind tunnel.

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Section: Introductionsupporting

confidence: 54%

The low frequency pressure pulsation and control of the open-jet wind tunnel

Luo

Leng

et al. 2022

Sci Rep

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“…Low-frequency pressure fluctuation is a common phenomenon in open-jet wind tunnels, characterized by periodic low-frequency pressure oscillations within a certain range of test wind speeds [5,8,[13][14][15][16]. The acoustic wavelength corresponding to the pulsating frequency is usually close to one order of magnitude of the plenum scale.…”

Section: Low-frequency Pressure Fluctuation In Open-jet Wind Tunnelmentioning

confidence: 99%

“…Low-frequency pressure fluctuations are also prevalent in automotive wind tunnels, which usually use 3/4-opening jet wind tunnels (square jets, and one side of the jet is at ground level, while the other three sides are free jet surfaces) [5,7,8,[13][14][15]26,27]. The S2A automotive wind tunnel located in Montigny-le-Bretonne, France, identified four distinct oscillation zones within the wind speed range of 10 m/s to 60 m/s.…”

Section: Low-frequency Pressure Fluctuation In Open-jet Wind Tunnelmentioning

confidence: 99%

“…The plenum of an open-jet wind tunnel used for acoustic testing is typically equipped with sound-absorbing wedges on its interior walls and is commonly referred to as either an anechoic plenum or a chamber [2]. Open jet wind tunnels find extensive applications in automotive wind tunnels [5][6][7][8], acoustics wind tunnels [7,[9][10][11], and certain specialized wind tunnels [12] due to their low blockage ratio, ease of test model installation and implementation, and large variable angle range of models compared to closed wind tunnels.…”

Section: Introduction 1open Jet Wind Tunnelmentioning

confidence: 99%

See 1 more Smart Citation

Review of Mechanisms and Suppression Methods for Low-Frequency Pressure Fluctuations in Open-Jet Wind Tunnels

Jin,

Deng,

Wang

et al. 2023

Applied Sciences

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Low-frequency pressure fluctuations are common in open-jet wind tunnels, affecting test accuracy and posing safety risks to the wind tunnels. These oscillations can be caused by different mechanisms in different wind tunnels, and it is often necessary to identify the specific mechanism responsible for the oscillation and develop appropriate control methods. This paper presents a comprehensive review of the current state of research on low-frequency pressure fluctuations in subsonic open-jet wind tunnels, with a particular emphasis on their generation mechanisms and control strategies. The primary source of excitation is attributed to the edgetone feedback formed by the impingement of the jet on the collector. The sound wavelength corresponding to the edgetone frequency is close to that of the plenum scale, facilitating resonance with both plenum-associated vibration modes and specific-order standing wave modes within the circuit loop, resulting in significant low-frequency pulsations. Passive control methods such as nozzle vortex generators and collector breathing gaps have been extensively employed due to their cost-effectiveness and efficiency. The concluding section highlights some unresolved issues that require further investigation in this field.

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“…In China, Jia et al at Tongji University have done a lot of experimental research in a 3/4 open-jet wind automobile tunnel. The mechanism of low frequency pressure oscillation was explained by investigating the sound pressure spectrum, pressure oscillation coefficient, and the migration of the main frequency of the low frequency oscillation with the wind speed [9,10].…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Low Frequency Oscillation in an Aeroacoustic Wind Tunnel

Li²,

Han³

et al. 2022

J. Phys.: Conf. Ser.

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The low frequency pressure oscillation in an aeroacoustic wind-tunnel seriously affects the flow quality and acoustic measurement. At present, there are many measures to suppress pressure oscillation, but due to the lack of in-depth understanding of its generation mechanism, these methods are not of general significance. In this paper, based on the open-source software OpenFOAM, the SA-DDES method is used for the unsteady computations for the two-dimensional simplified wind-tunnel model. The steady and unsteady fields inside and outside the jet flow are showed. The computational results show that the nonlinear interaction between the large scale vortices rolled up by the instabilities of the shear layer and the front wall of the collector of the wind-tunnel is the main reason responsible for the low frequency oscillation in an aeroacoustic wind-tunnel. In addition, it is concluded that in the feedback loop path of the excitation-feedback effect, the pressure waves produced by the large scale vortex structures inside the shear layer impinging on the front wall of the collector are reflected by the rear wall of the plenum chamber. The end of the path that the pressure waves travel upstream is where vortex shedding happens, not the nozzle exit.

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On the Low Frequency Pressure Fluctuation in a 3/4 Open Jet Automotive Wind Tunnel

Cited by 7 publications

References 15 publications

The low frequency pressure pulsation and control of the open-jet wind tunnel

The low frequency pressure pulsation and control of the open-jet wind tunnel

Review of Mechanisms and Suppression Methods for Low-Frequency Pressure Fluctuations in Open-Jet Wind Tunnels

Numerical Simulation of Low Frequency Oscillation in an Aeroacoustic Wind Tunnel

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