Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
An Assessment of Detached-Eddy Simulations of Unsteady Crosswind Aerodynamics of Road Vehicle
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aeroacoustics.ORCID iD: 0000-0002-9061-4174
2011 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 87, no 1, 133-163 p.Article in journal (Refereed) Published
Abstract [en]

An extensive study of the mesh requirements when simulating unsteady crosswind aerodynamics for industrial applications is conducted and reported in this article. Detached-Eddy Simulations (DES) of a simple car geometry under headwind, steady crosswind and time-dependent wind gust are analysed for different meshes and flow cases using a commercial software, STAR-CD. The typical Reynolds number of the cases studied is 2.0x106 based on the vehicle length. Mesh requirements for capturing the time development of the flow structures during a gust is provided. While respecting these requirements, the aerodynamic coefficients can be reliably calculated. Using turbulence methods like DES in order to resolve the flow scales provides a significant insight for designing a ground vehicle and, due to the reasonable computational times involved, can be incorporated in a design process in a near future.

Place, publisher, year, edition, pages
2011. Vol. 87, no 1, 133-163 p.
Keyword [en]
Unsteady crosswind aerodynamics, Detached-Eddy Simulation, Wind gust, Mesh, Vehicle aerodynamics
National Category
Vehicle Engineering Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-11323DOI: 10.1007/s10494-011-9333-4ISI: 000291661700006Scopus ID: 2-s2.0-79959308216OAI: oai:DiVA.org:kth-11323DiVA: diva2:273712
Projects
ECO2 crosswind stability and unsteady aerodynamics
Funder
Swedish e‐Science Research CenterTrenOp, Transport Research Environment with Novel Perspectives
Note
QC 20101012 Updated from submitted to published.Available from: 2009-10-23 Created: 2009-10-23 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Numerical Investigation of Unsteady Crosswind Aerodynamics for Ground Vehicles
Open this publication in new window or tab >>Numerical Investigation of Unsteady Crosswind Aerodynamics for Ground Vehicles
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Ground vehicles are subjected to crosswind from various origins such as weather, topography of the ambient environment (land, forest, tunnels, high bushes...) or surrounding traffic. The trend of lowering the weight of vehicles imposes a stronger need for understanding the coupling between crosswind stability, the vehicle external shape and the dynamic properties. Means for reducing fuel consumption of ground vehicles can also conflict with the handling and dynamic characteristics of the vehicle. Streamlined design of vehicle shapes to lower the drag can be a good example of this dilemma. If care is not taken, the streamlined shape can lead to an increase in yaw moment under crosswind conditions which results in a poor handling.

The development of numerical methods provides efficient tools to investigate these complex phenomena that are difficult to reproduce experimentally. Time accurate and scale resolving methods, like Detached-Eddy Simulations (DES), are particularly of interest, since they allow a better description of unsteady flows than standard Reynolds Average Navier-Stokes (RANS) models. Moreover, due to the constant increase in computational resources, this type of simulations complies more and more with industrial interests and design cycles.

In this thesis, the possibilities offered by DES to simulate unsteady crosswind aerodynamics of simple vehicle models in an industrial framework are explored. A large part of the work is devoted to the grid design, which is especially crucial for truthful results from DES. Additional concerns in simulations of unsteady crosswind aerodynamics are highlighted, especially for the resolution of the wind-gust boundary layer profiles. Finally, the transient behaviour of the aerodynamic loads and the flow structures are analyzed for several types of vehicles. The results simulated with DES are promising and the overall agreement with the experimental data available is good, which illustrates a certain reliability in the simulations. In addition, the simulations show that the force coefficients exhibit highly transient behaviour under gusty conditions.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. xi, 39 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2009:68
Keyword
Aerodynamics, Vehicle Aerodynamics, Unsteady Aerodynamics, Crosswind, Unsteady Crosswind Aerodynamics, Detached-Eddy Simulations, DES
National Category
Vehicle Engineering Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-11311 (URN)978-91-7415-446-7 (ISBN)
Presentation
2009-11-12, E52, Oscars Backe 14, 3tr, KTH-Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
ECO2 Crosswind Stability and Unsteady Aerodynamics for Ground Vehicles
Available from: 2009-10-23 Created: 2009-10-21 Last updated: 2010-10-12Bibliographically approved
2. Aerodynamics simulations of ground vehicles in unsteady crosswind
Open this publication in new window or tab >>Aerodynamics simulations of ground vehicles in unsteady crosswind
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ground vehicles, both on roads or on rail, are sensitive to crosswinds and the handling, travelling speeds or in some cases, safety can be affected. Full modelling of the crosswind stability of a vehicle is a demanding task as the nature of the disturbance, the wind gust, is complex and the aerodynamics, vehicle dynamics and driver reactions interact with each other. 

One of the objectives of this thesis, is to assess the aerodynamic response of simplified ground vehicles under sudden strong crosswind disturbances by using an advanced turbulence model. In the aerodynamic simulations, time-dependant boundary data have been used to introduce a deterministic wind gust model into the computational domain. 

This thesis covers the implementation of such gust models into Detached-Eddy Simulations (DES) and assesses the overall accuracy. Different type of grids, numerical setups and refinements are considered. Although the overall use of DES is seen suitable, further investigations can be foreseen on more challenging geometries. 

Two families of vehicle models have been studied. The first one, a box-like geometry, has been used to characterize the influence of the radius of curvature and benefited from unsteady experimental data for comparison. The second one, the Windsor model, has been used to understand the impact of the different rear designs. Noticeably, the different geometries tested have exhibited strong transients in the loads that can not be represented in pure steady crosswind conditions.

The static coupling between aerodynamics and vehicle dynamics simulations enhances the comparisons of the aerodynamic designs. Also, it shows that the motion of the centre of pressure with respect the locations of the centre of gravity and the neutral steer point, is of prime interest to design vehicles that are less crosswind sensitive. Recommendations on the future work on crosswind sensitivity for ground vehicles are proposed at the end of this thesis.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. xx, 67 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2011:82
Keyword
Detached-Eddy Simulations; Crosswind; Aerodynamics;
National Category
Aerospace Engineering Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-50242 (URN)978-91-7501-196-7 (ISBN)
Public defence
2011-12-16, E1, Lindstedsvägen 3, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Projects
crosswind stability and unsteady aerodynamics
Note

QC 20111206

Available from: 2011-12-06 Created: 2011-12-03 Last updated: 2013-06-25Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Authority records BETA

Efraimsson, Gunilla

Search in DiVA

By author/editor
Favre, TristanEfraimsson, Gunilla
By organisation
AerodynamicsVinnExcellence Center for ECO2 Vehicle designAeroacoustics
In the same journal
Flow Turbulence and Combustion
Vehicle EngineeringFluid Mechanics and Acoustics

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 370 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf