On Low-Frequency Pressure Pulsations and Static Pressure Distribution in Open Jet Automotive Wind Tunnels

Arnette, Stephen A.; Buchanan, T. D.; Zabat, Michael

doi:10.4271/1999-01-0813

Cited by 28 publications

(11 citation statements)

References 10 publications

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“…The ratio of this model wind tunnel is 1/7. The main purpose is to test a variety of means to suppress low-frequency buffeting, and also analyze the possible mechanism of pressure pulsation (Manuel et al, 1992;Arnette et al, 1999). The result given by the different jet lengths shows that the low-frequency buffeting phenomenon is related to the distance between the nozzle and the collector.…”

Section: Introductionmentioning

confidence: 99%

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

Jia

Zhu

Bao

et al. 2019

JAFM

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In the present research, a possible generation mechanism of low-frequency buffeting phenomenon based on a 1:15 open jet automotive wind tunnel was investigated. Evolution of vortex structures and pressure field in the plenum chamber have been visualized and analyzed by Large-eddy simulation (LES). It is shown that the low frequency pressure fluctuation is caused by the largescale structures and their interaction. Multiple proper orthogonal decomposition was adopted to analyze the flow field in the plenum chamber. The characteristic frequencies of the vortex-rings after pairing is the same as the dominant resonance of buffeting at this wind velocity.

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Section: Introductionmentioning

confidence: 99%

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

Jia

Zhu

Bao

et al. 2019

JAFM

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“…Low-frequency pulsations can also be an issue in an aeroacoustic wind tunnel and a range of studies have been carried out to minimise these effects. In a study by Arnette et al (1999), it was found that whilst the underlying physics of these pulsations is not fully understood, the pulsations originate as coherent vortex structures generated at the nozzle, which then travel through the test section at a fraction of the jet speed, before impinging on the collector. These can then couple with other acoustic modes Passively, low-frequency buffeting can also be suppressed using a tuned Helmholtz resonator, which was demonstrated to reduce buffeting by 10 dB, from Beland (2007).…”

Section: Aeroacousticsmentioning

confidence: 99%

The Effects of Unsteady On-Road Flow Conditions on Cabin Noise

Oettle¹,

Sims-Williams²,

Dominy³

et al. 2010

SAE Technical Paper Series

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On-road, a vehicle experiences unsteady flow conditions due to turbulence in the natural wind, moving through the unsteady wakes of other road vehicles and travelling through the stationary wakes generated by roadside obstacles. There is increasing concern about potential differences between steady flow conditions that are typically used for development and the transient conditions that occur on-road. This work considers whether steady techniques are able to predict the unsteady results measured on-road, the impact of this unsteadiness on the noise perceived in the cabin and whether minor changes made to the geometry of the vehicle could affect this. Both external aerodynamic and acoustic measurements were taken using a full-size vehicle combined with measurements of the noise inside the cabin. Data collection took place on-road under a range of wind conditions to accurately measure the response of the vehicle to oncoming flow unsteadiness, with steady-state measurements taking place in full-scale aeroacoustic wind tunnels.Overall it was demonstrated that, using a variety of temporal and spectral approaches, steady techniques were able to predict unsteady on-road results well enough to assess cabin noise by correctly taking into account the varying on-road flow conditions. Aerodynamic admittance values remained less than unity in the sideglass region of the vehicle, with the exception of the the region nearest the A-pillar. The reducing unsteady energy at frequencies greater than 10 Hz, combined with the corresponding roll-off in admittance, implies that unsteady frequencies below 10 Hz affect the vehicle most, where the response remains quasi-steady.Quasi-steady cabin noise simulations allowed a subjective assessment of the predicted unsteady cabin noise, where the impact of cabin noise modulations were quantified and found to be important to perception. Minor geometry changes affected the sensitivity of cabin noise to changes in yaw angle, altering modulation and therefore having an important impact on the unsteady wind noise perceived on-road.iii DeclarationThe work in this thesis is based on research carried out at the School of Engineering and Computing Sciences, Durham University, UK. No part of this thesis has been submitted elsewhere for any other degree or qualification and it all my own work unless referenced to the contrary in the text.

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“…Efforts to understand the physics and to reduce the impact of those low frequency fluctuations on data quality and wind tunnel operation have been reported in many recent technical papers (Arnette and Buchanan, 1999;Wickern et al, 2000;Rennie et al, 2004;von Heesen and Höpfer, 2000).…”

Section: Introductionmentioning

confidence: 99%