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Assessing the Aeroacoustic Response of a Vehicle to Transient Flow Conditions from the Perspective of a Vehicle Occupant

Oettle, N.R.; Sims-Williams, D.B.; Dominy, R.G.

Assessing the Aeroacoustic Response of a Vehicle to Transient Flow Conditions from the Perspective of a Vehicle Occupant Thumbnail


Authors

N.R. Oettle

R.G. Dominy



Abstract

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. Separated flow structures in the sideglass region of a vehicle are particularly sensitive to unsteadiness in the onset flow. These regions are also areas where strong aeroacoustic effects can exist, in a region close to the passengers of a vehicle. The resulting aeroacoustic response to unsteadiness can lead to fluctuations and modulation at frequencies that a passenger is particularly sensitive towards. Results presented by this paper combine on-road measurement campaigns using instrumented vehicles in a range of different wind environments and aeroacoustic wind tunnel tests. A new cabin noise simulation technique was developed to predict the time-varying wind noise in a vehicle using the cabin noise measured in the steady environment of the wind tunnel, and a record of the unsteady onset conditions on the road, considering each third-octave band individually. The simulated cabin noise predicted using this quasi-steady technique was compared against direct on-road cabin noise measurements recorded under the same flow conditions to assess the response of the vehicle to oncoming flow unsteadiness. The technique predicted the modulation of the wind noise under unsteady on-road conditions with good fidelity. This is because the cabin noise response to oncoming flow unsteadiness remained generally quasi-steady up to fluctuation frequencies of approximately 2 to 5 Hz, with fluctuations at higher scales having a progressively smaller impact, and because most of the onset flow fluctuation energy on the road occurs at frequencies below this threshold. The relative impact of the baseline level of cabin noise and the sensitivity of the cabin noise to changes in yaw angle were assessed in terms of occupant perception and this highlighted the importance of modulation. This can provide guidance when assessing the on-road wind noise performance of vehicle geometry modifications and of different vehicles.

Citation

Oettle, N., Sims-Williams, D., & Dominy, R. (2014). Assessing the Aeroacoustic Response of a Vehicle to Transient Flow Conditions from the Perspective of a Vehicle Occupant. SAE International Journal of Passenger Cars - Mechanical Systems, 7(2), 550-558. https://doi.org/10.4271/2014-01-0591

Journal Article Type Article
Online Publication Date Apr 1, 2014
Publication Date Jan 4, 2014
Deposit Date Dec 31, 2014
Publicly Available Date Jan 30, 2015
Journal SAE International Journal of Passenger Cars - Mechanical Systems
Print ISSN 1946-3995
Electronic ISSN 1946-4002
Publisher SAE International
Peer Reviewed Peer Reviewed
Volume 7
Issue 2
Pages 550-558
DOI https://doi.org/10.4271/2014-01-0591
Public URL https://durham-repository.worktribe.com/output/1414858

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