This 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.
Cross Winds and Transients: Reality, Simulation and Effects
Sae International Journal of Passenger Cars. Mechanical Systems
Sae Int. J. Passeng. Cars – Mech. Syst
SAE 2011 World Congress & Exhibition ; 2011
Sae International Journal of Passenger Cars - Mechanical Systems ; 4 , 1 ; 172-183
2011-04-12
12 pages
Aufsatz (Konferenz)
Englisch
2011-01-0172 Cross Winds and Transients: Reality, Simulation and Effects
British Library Conference Proceedings | 2011
|Cross wind and transients: reality, simulation and effects
Kraftfahrwesen | 2011
|Passenger Vehicles in Unsteady Cross Winds
British Library Conference Proceedings | 1994
|Software Simulation for Hydraulic Transients
SAE Technical Papers | 1988
|Numerical simulation of side winds effects on high speed trains
Kraftfahrwesen | 1997
|