Turbulent dispersion of particulates in the Ahmed body wake and effects of moving ground

This study investigates the influence of wind tunnel ground conditions on smoke particle dispersion and concentration fields in the near wake of a simplified vehicle model (Ahmed body). The effects of wind tunnel ground conditions are investigated with the implementation of a rolling road and boundary layer suction system inside the wind tunnel. In experiments, smoke particles were released from a source and illuminated with a laser sheet. The concentration of smoke particles was measured using a Mie-scattering-based concentration measurement technique. Concentration fields and particle dispersion were measured at six downstream positions in the near wake of Ahmed body at Rel=1.21×105 (based on model length). The concentration fields obtained were used to calculate dispersion parameters, such as the smoke spread in vertical (Sy) and lateral (Sz) directions. The findings indicate that the concentration fields and dispersion parameters in the near wake are highly dependent on the wind tunnel ground conditions. Particularly enhancing vertical spread under stationary ground conditions while showing minimal effect on lateral spread. It was observed that the maximum increase in the vertical spread is ≈29% for the stationary case. Notably, the lateral spread (Sz) is consistently greater than the vertical spread (Sy), regardless of downstream location or ground condition. The results underscore the critical influence of the correct choice of wind tunnel ground conditions in dispersion studies.