The Effect of Free Stream Turbulence on A-pillar Airflow

Howell, Jeff; Fuller, Joshua Baden; Passmore, Martin A.

doi:10.4271/2009-01-0003

Cited by 9 publications

(12 citation statements)

References 11 publications

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“…This investigation was extended to visualise flow using PIV and found that increased turbulence intensity alters the nature of the flow separation. Further work by Howell et al (2009) and found that oncoming unsteadiness reduced the vortex suction, but increased the RMS pressure fluctuations, although not the peak pressures. Mean pressures are related to door loads and can change the sealing properties of the door, leading to increased leak noise.…”

Section: Aeroacousticsmentioning

confidence: 96%

“…Sound intensity probe with microphones with nose cones in parallel set-up above the exterior mirror of a passenger vehicle [8]…”

Section: Fig 13mentioning

confidence: 99%

“…Sound intensity level along the side of a passenger vehicle with an exterior loudspeaker integrated into the door which reflects towards the outside; loudspeaker output: tone at 5 kHz; distance from vehicle surface: 300 mm [8] 1 As sound is deflected by the airflow, the probe must be positioned further downstream compared to a measurement without flow. Moreover, the microphone which is more distant to the loudspeaker must be displaced a small distance further back compared to the other microphone according to the sound deflection angle, in order to adapt the measuring direction of the probe.…”

Section: Fig 14mentioning

confidence: 99%

“…For example, work byHowell et al (2009) and Baden Fuller (2009) used grids to generate turbulence during a vehicle A-pillar study. Using 25 mm bars, length scales of up to 37 mm were generated.…”

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confidence: 99%

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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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Section: Aeroacousticsmentioning

confidence: 96%

“…Sound intensity probe with microphones with nose cones in parallel set-up above the exterior mirror of a passenger vehicle [8]…”

Section: Fig 13mentioning

confidence: 99%

Section: Fig 14mentioning

confidence: 99%

mentioning

confidence: 99%

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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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“…The subsequent pressure loading in the region affects door loads and can change the sealing properties of the door. Larger scale flow unsteadiness (eg: as experienced on-road) will tend to increase pressure fluctuations and modulations of wind noise [47][48][49][50] .…”

Section: Vehicle Formmentioning

confidence: 99%

Automotive aeroacoustics: An overview

Oettle

Sims-Williams

2017

Proceedings of the Institution of Mechanical Engineers, Part D:

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractVehicle aeroacoustic performance has a strong influence on customer perception and also has importance for safety and comfort. Wind noise performance was once differentiated by the quality of sealing. Today, achieving competitive wind noise performance also depends on minimising aeroacoustic noise sources generated by the vehicle form, and on attenuation in the noise pathway from sources on the exterior to the vehicle interior. Attenuation in the noise pathway from sources on the exterior to the vehicle interior, especially through glazed surfaces, will continue to play an important role in controlling cabin noise, with a particular emphasis on achieving attenuation efficiently in terms of component mass. The human brain is not only sensitive towards the level of steady broadband noise, but distinctive features such as tonality or modulation draw the attention of the vehicle occupant and impact negatively on perception. Complex indices are often required to define good wind noise performance. This includes the consideration of multiple frequency bands and effects of the range of yaw angles experienced on-road. A key to achieving future vehicle refinement is bringing together an understanding of unsteady onset flow conditions, their impact on cabin sound pressure level and modulation and in turn the impact of noise level and modulation on psychoacoustic perception.

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