An LES investigation of the near-wake flow topology of a simplified heavy vehicle

Artikel i vetenskaplig tidskrift, 2019

Recent experimental investigations of McArthur et al (2016) in the wake of a simplified heavy vehicle or commonly known as the ground transportation
system (GTS) model has shown that the flow topology is invariant over a large range of Reynolds numbers [2.7 × 104 − 2 × 106]. Numerical simulations are performed to investigate the initial flow topology at a Reynolds number of 2.7× 104, using well-resolved large eddy simulations (LES). In the vertical midplane behind the GTS, a flow state which is anti-symmetric to that reported in McArthur et al (2016) is observed here, thereby, confirming the possibility of occurrence of the complementary bi-stable flow state. The occurrence of this bi-stable state does not depend on the ground clearance between the GTS and the ground plane, as a similar flow topology is observed at both small and large gap heights. Furthermore, the flow topology in the vertical midplane is also found to be insensitive to the incoming flow for small yaw angles. However, complex flow behaviour is observed in the wake for larger yaw angles, where the flow topology in the vertical midplane becomes nearly symmetric, while an asymmetric flow topology is now observed in the lateral midplane in the near wake. Furthermore, the corner vortices which originate from either side at the front of the model merge in the far wake, leading to a large vortex structure nearly equal to the height of the model. The near-wake topology of the GTS is analysed and compared with previous studies for a range of scenarios, and the forces on the GTS are computed.