Numerical Simulations of the Flow around a Yawing Truck in Wind Tunnel
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Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Automotive engineering (MPAUT), MSc
Publicerad
2011
Författare
Mu, Xinke
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Ground vehicles such as cars and heavy trucks travelling on road are often exposed to unsteady flows. Particularly, the oscillation of vehicles in the vertical direction (maybe caused by side force from being subjected to strong gusty wind, or bumpy road) can produce time-dependent flow condition. This kind of transient force also occurs in the experiment tests with a rotating vehicle for getting variable yaw angle. Although the oscillation speed in the experiment is fairly low, however the unsteady flow conditions can lead to an intersection between the flow and vehicle movement. This intersection thus will change how the aerodynamic forces and moments will be developed. Therefore, in order to study the effects of vehicle oscillation on flow development and predict the aerodynamic force at steady condition, both steady and transient dynamic simulation were conducted. All simulations are based on the experiment scenario carried out with a Volvo heavy truck in the RUAG wind tunnel. However, the oscillation frequency in the experiment is too low, so a higher oscillation frequency was adopted in the transient dynamic simulation in order to accomplish the simulation in a reasonable time. k − ζ − f eddy-viscosity turbulence model were adopted in all steady and transient simulation due to its accuracy and robustness at high Reynolds number (Re = 6.68 ∗ 106) Surface meshes were repaired and modified in ANSA and AVL-Fire, volume meshes were generated using FAMEHexa provided by AVL List GmbH, and AVL-Fire were used as the CFD solver. For the steady simulations, drag, yaw moment and flow field were estimated for 0 and 5 degree yaw angle. For the transient dynamic simulation, mesh deformation method was used to simulate the vehicle’s yaw movement. The oscillation frequency of f = 2Hz was chosen to correspond to the Strouhal number St = fL/U∞ = 0.18.
Beskrivning
Ämne/nyckelord
Hållbar utveckling , Transport , Strömningsmekanik , Sustainable Development , Transport , Fluid mechanics