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An Assessment of Detached-Eddy Simulations of Unsteady Crosswind Aerodynamics of Road Vehicle
KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aerodynamik. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Aeroakustik.ORCID-id: 0000-0002-9061-4174
2011 (engelsk)Inngår i: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 87, nr 1, s. 133-163Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
2011. Vol. 87, nr 1, s. 133-163
Emneord [en]
Unsteady crosswind aerodynamics, Detached-Eddy Simulation, Wind gust, Mesh, Vehicle aerodynamics
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-11323DOI: 10.1007/s10494-011-9333-4ISI: 000291661700006Scopus ID: 2-s2.0-79959308216OAI: oai:DiVA.org:kth-11323DiVA, id: diva2:273712
Prosjekter
ECO2 crosswind stability and unsteady aerodynamics
Forskningsfinansiär
Swedish e‐Science Research CenterTrenOp, Transport Research Environment with Novel Perspectives
Merknad
QC 20101012 Updated from submitted to published.Tilgjengelig fra: 2009-10-23 Laget: 2009-10-23 Sist oppdatert: 2017-12-12bibliografisk kontrollert
Inngår i avhandling
1. Numerical Investigation of Unsteady Crosswind Aerodynamics for Ground Vehicles
Åpne denne publikasjonen i ny fane eller vindu >>Numerical Investigation of Unsteady Crosswind Aerodynamics for Ground Vehicles
2009 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Stockholm: KTH, 2009. s. xi, 39
Serie
Trita-AVE, ISSN 1651-7660 ; 2009:68
Emneord
Aerodynamics, Vehicle Aerodynamics, Unsteady Aerodynamics, Crosswind, Unsteady Crosswind Aerodynamics, Detached-Eddy Simulations, DES
HSV kategori
Identifikatorer
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 (engelsk)
Opponent
Veileder
Prosjekter
ECO2 Crosswind Stability and Unsteady Aerodynamics for Ground Vehicles
Tilgjengelig fra: 2009-10-23 Laget: 2009-10-21 Sist oppdatert: 2010-10-12bibliografisk kontrollert
2. Aerodynamics simulations of ground vehicles in unsteady crosswind
Åpne denne publikasjonen i ny fane eller vindu >>Aerodynamics simulations of ground vehicles in unsteady crosswind
2011 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2011. s. xx, 67
Serie
Trita-AVE, ISSN 1651-7660 ; 2011:82
Emneord
Detached-Eddy Simulations; Crosswind; Aerodynamics;
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-50242 (URN)978-91-7501-196-7 (ISBN)
Disputas
2011-12-16, E1, Lindstedsvägen 3, KTH, Stockholm, 14:00 (engelsk)
Opponent
Veileder
Prosjekter
crosswind stability and unsteady aerodynamics
Merknad

QC 20111206

Tilgjengelig fra: 2011-12-06 Laget: 2011-12-03 Sist oppdatert: 2013-06-25bibliografisk kontrollert

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