Three Dimensional Dynamics in the Wake of an Ahmed Body

Overview & Synopsis

A flow around a squareback Ahmed body is simulated with a DNS using the 3D parallel in-house code SUNFLUIDH. A penalization method is applied for the body. The DNS recovers the deviation of the wake observed experimentally [1]. POD is first applied in a plane section in the near wake at mid-height of the body and allows a comparison with experiments. The spatial modes and the histograms of the amplitudes are similar and two main frequencies are extracted, which are related to vortex shedding and wake pumping phenomena. A 3-D POD is then applied to the full velocity field and leads to a better understanding of the deviation phenomenon, linked to the second mode. Moreover, a POD-based low dimensional model captures the main frequencies of the modes in the simulation and correctly estimates the energetic content. This shows the predictive ability of the model.