A New Technique to Measure the Aerodynamic Response of Passenger Cars by a Continuous Flow Yawing

Carlino, G.; Cardano, D.; Cogotti, A.

doi:10.4271/2007-01-0902

Cited by 26 publications

(10 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Such devices are capable of generating the large length scales representative of the majority of on-road gusts. In addition, it has been shown that active drag-based devices such as the upstream deployable blades at Pininfarina [20,21] can be used to generate dynamically yawing flow by controlling the relative phasing of the opening and closing of the blades [22].…”

Section: Introductionmentioning

confidence: 99%

A Fully Coupled, 6 Degree-of-Freedom, Aerodynamic and Vehicle Handling Crosswind Simulation using the DrivAer Model

Forbes¹,

Page²,

Passmore³

et al. 2016

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

View full text Add to dashboard Cite

INTRODUCTIONIn the UK, average annual wind speeds fall in the range of 4-5m/s, which at typical vehicle speeds of 100km/h can produce flow yaw angles up to 10° [1]. In contrast, maximum mean hourly wind speeds of up to 24m/s over flat, open, central parts of the UK have been recorded, albeit with a probability of occurring once in 50-year period [1,2]. Whilst data describing instantaneous peak values is rare, values greater than this mean can be expected. Nevertheless, these speeds correspond to a much larger maximum flow yaw angle of approximately 40°. Such high angles and speeds present a safety concern as it will be shown that at these values, the forces acting on the vehicle are large enough to cause a substantial course deviation and in some cases, are large enough for the vehicle to encroach upon adjacent lanes.This issue will become even more prevalent with the current trend towards lighter, more fuel efficient vehicles, in a bid to meet emissions regulations brought about by the `Worldwide Harmonized Light Vehicles Test Procedure' (WLTP) [3].It is generally assumed that as any lateral or yaw accelerations are sensed a driver will be able to provide an adequate counter response to a gust to prevent a significant deviation. However, this is not always the case because when the frequency of the gust is combined with the drivers inputs the driver's response can amplify the vehicle's deviation. This is shown by Wagner and Wiedemann [4], within a frequency range of 0.5-2Hz, to occur as the vehicle motion due to the crosswind and the driver's steering input approach an in-phase state, peaking at a frequency of 1.4Hz. For frequencies <0.5Hz, the driver typically has a positive influence on the vehicle's response, as the gust and loads acting on the vehicle are quasi-steady. Whereas at higher frequencies >2Hz, the driver has little to no influence, as the gust has passed before it is felt.In order to assess the complete vehicle-driver response to such an event, a flow disturbance has to be generated, either naturally or artificially. The aerodynamic response of a vehicle during a crosswind has been investigated using numerous methods. On road vehicle testing [5,6,7,8,9] is often preferred as it places a representative driver and vehicle in a real-world environment, whilst crosswind generators beside test tracks [10,11] offer a degree of control over gust parameters.An International Standard ISO 12021:2010 [13] has been derived in an attempt to standardize such facilities. These guidelines appear to be based on the work of Howell [11], in which a trifurcated tail pipe attached to the exhaust of a jet engine was used to determine the behavior of a small Sports Utility Vehicle (SUV) when passing Adrian P. Gaylard Jaguar Land Rover ABSTRACTIn a real-world environment, a vehicle on the road is subjected to a range of flow yaw angles, the most severe of which can impact handling and stability. A fully coupled, six degrees-of-freedom CFD and vehicle handling simulation has modelled the complete closed loop system. Vary...

show abstract

Section: Introductionmentioning

confidence: 99%

A Fully Coupled, 6 Degree-of-Freedom, Aerodynamic and Vehicle Handling Crosswind Simulation using the DrivAer Model

Forbes¹,

Page²,

Passmore³

et al. 2016

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

View full text Add to dashboard Cite

show abstract

“…While drag devices can produce longitudinal scales at the frequency of operation, they simultaneously produce shorter scales from unsteady flow over the bluff geometries. In the Pininfarina TGS (Figure 11) some modes of operation can be used to generate lateral turbulence (Carlino et al [55]) with wavelengths equivalent to approximately 12-100 vehicle lengths. That work reported dynamic yawing moments at particular conditions which were almost 40% greater than would be predicted by quasisteady theory.…”

Section: Stationary Turbulence -Central Scalesmentioning

confidence: 99%

Cross Winds and Transients: Reality, Simulation and Effects

Sims-Williams

2011

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

View full text Add to dashboard Cite

Additional information:Use policyThe 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. ABSTRACTThis paper provides a published counterpart to the address of the same title at the 2010 SAE World Congress.A vehicle on the road encounters an unsteady flow due to turbulence in the natural wind, due to the unsteady wakes of other vehicles and as a result of traversing through the stationary wakes of road side obstacles. This last term is of greatest significance.Various works related to the characterization, simulation and effects of on-road turbulence are compared together on the turbulence spectrum to highlight differences and similarities. The different works involve different geometries and different approaches to simulating cross wind transients but together these works provide guidance on the most important aspects of the unsteadiness.On-road transients include a range of length scales spanning several orders of magnitude but the most important scales are in the in the 2-20 vehicle length range. There are significant levels of unsteadiness experienced on-road in this region and the corresponding frequencies are high enough that a dynamic test is required to correctly determine the vehicle response. Fluctuations at these scales generate significant unsteady loads (aerodynamic admittance typically 0.6-1.4) and the corresponding frequencies can adversely affect vehicle dynamics.The generation of scales larger than the scale of the vehicle is impractical with passive grids and so active turbulence generation systems are preferred. These can be classified into lift and drag-based devices. Lift-based devices provide better control of the turbulence but can only just reproduce the smaller scales in the 2-20 vehicle length range. Different moving model approaches are also discussed. CFD offers real advantages through its ability to allow arbitrary time-varying boundary conditions.

show abstract

“…It is widely considered, for instance by Cooper and Watkins (2007), that the variation in wind speed Wind at a particular measurement point is normally distributed, follow- angles was also present in the on-road data presented by Carlino et al (2007). This implies that the distribution of wind direction relative to the vehicle is not uniform.…”

Section: On-roadmentioning

confidence: 99%

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

Oettle¹,

Sims-Williams²,

Dominy³

et al. 2010

SAE Technical Paper Series

View full text Add to dashboard Cite

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.

show abstract

A New Technique to Measure the Aerodynamic Response of Passenger Cars by a Continuous Flow Yawing

Cited by 26 publications

References 9 publications

A Fully Coupled, 6 Degree-of-Freedom, Aerodynamic and Vehicle Handling Crosswind Simulation using the DrivAer Model

A Fully Coupled, 6 Degree-of-Freedom, Aerodynamic and Vehicle Handling Crosswind Simulation using the DrivAer Model

Cross Winds and Transients: Reality, Simulation and Effects

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

Contact Info

Product

Resources

About