Flow structures in the near-wake of the Ahmed model

The time-averaged and time-dependent nature of the Ahmed model near- and far-wake has been investigated experimentally. The use of a new multi-hole probe allowed for measurement in regions exhibiting large flow angles (including flow reversals), and high levels of unsteadiness, allowing examination of flow regions previously difficult to investigate. Although time-averaged results of the far-wake showed good agreement with previously published work, the near-wake structure was found to be somewhat different, with much of the inconsistency being found in the interaction between a separated region over the slant and the recirculatory flows behind the model. Time-dependant analysis revealed that the shedding behind the model is analogous to vortex shedding behind bluff bodies, with most of the fluctuations confined to the axial direction. In addition, the shedding characteristics on the slant showed very similar behaviour to the vertical base, indicating strong turbulent mixing between the two regions, emphasizing time-averaged findings.

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