The Bandwidth of Transient Yaw Effects on Vehicle Aerodynamics

Mankowski, Oliver; Sims-Williams, David; Dominy, Robert; Duncan, Bradley D.; Gargoloff, Joaquin

doi:10.4271/2011-01-0160

Cited by 8 publications

(5 citation statements)

References 12 publications

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“…At smaller angles, the elements act as lift devices, whilst at larger angles, the flow becomes separated and acts as a 1.4 The Unsteady Environment drag device. This approach attempts to bridge the gap between simulating longer and shorter length scales, although as stated by Mankowski et al (2011), it is the intermediate scales that still provide the greatest challenges.…”

Section: The Unsteady Environmentmentioning

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: The Unsteady Environmentmentioning

confidence: 99%

“…Therefore transient aeroacoustic simulations are not currently widespread. This contrasts with transient force investigations, which, owing to their more moderate computational requirements are becoming more common, including those ofTsubokura et al (2010),Gaylard et al (2010) andMankowski et al (2011).…”

mentioning

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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“…Operating in this mode allows operation at up to 10 Hz with aerofoil amplitude continuously variable up to ±15°. Mankowski et al [29] showed that non-linearities in bluff body response mean that it is not sufficient to consider yaw harmonics individually and independently. Therefore incorporating programmed non-harmonic motion was important in the specification and implementation of the system.…”

Section: Methodsmentioning

confidence: 99%

A Wind Tunnel Simulation Facility for On-Road Transients

Mankowski¹,

Sims-Williams²,

Dominy³

2014

SAE Int. J. Passeng. Cars - Mech. Syst.

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“…[16]. On the contrary, the aerodynamic development of vehicles typically takes place in wind tunnels or with the use of CFD techniques assuming ideal conditions (e.g., uniform flow), thus introducing discrepancies vis-à-vis the actual aerodynamic performance of a vehicle driven on the road [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo Simulation Methodology to Assess the Impact of Ambient Wind on Emissions from a Light-Commercial Vehicle Running on the Worldwide-Harmonized Light-Duty Vehicles Test Cycle (WLTC)

Zachiotis

Giakoumis

2021

Energies

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A Monte Carlo simulation methodology is suggested in order to assess the impact of ambient wind on a vehicle’s performance and emissions. A large number of random wind profiles is generated by implementing the Weibull and uniform statistical distributions for wind speed and direction, respectively. Wind speed data are drawn from eight cities across Europe. The vehicle considered is a diesel-powered, turbocharged, light-commercial vehicle and the baseline trip is the worldwide harmonized light-duty vehicles WLTC cycle. A detailed engine-mapping approach is used as the basis for the results, complemented with experimentally derived correction coefficients to account for engine transients. The properties of interest are (engine-out) NO and soot emissions, as well as fuel and energy consumption and CO2 emissions. Results from this study show that there is an aggregate increase in all properties, vis-à-vis the reference case (i.e., zero wind), if ambient wind is to be accounted for in road load calculation. Mean wind speeds for the different sites examined range from 14.6 km/h to 24.2 km/h. The average increase in the properties studied, across all sites, ranges from 0.22% up to 2.52% depending on the trip and the property (CO2, soot, NO, energy consumption) examined. Based on individual trip assessment, it was found that especially at high vehicle speeds where wind drag becomes the major road load force, CO2 emissions may increase by 28%, NO emissions by 22%, and soot emissions by 13% in the presence of strong headwinds. Moreover, it is demonstrated that the adverse effect of headwinds far exceeds the positive effect of tailwinds, thus explaining the overall increase in fuel/energy consumption as well as emissions, while also highlighting the shortcomings of the current certification procedure, which neglects ambient wind effects.

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The Bandwidth of Transient Yaw Effects on Vehicle Aerodynamics

Cited by 8 publications

References 12 publications

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

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

A Wind Tunnel Simulation Facility for On-Road Transients

Monte Carlo Simulation Methodology to Assess the Impact of Ambient Wind on Emissions from a Light-Commercial Vehicle Running on the Worldwide-Harmonized Light-Duty Vehicles Test Cycle (WLTC)

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