Structure of turbulent flows over two-dimensional bluff bodies inspired by a pickup truck geometry

Highlights: • Locations and sizes of the vortices did not change beyond half of bluff body height. • Vorticity and vortex sizes increased with the back plate height. • The reverse velocity in the wake increased with the cavity depth to a maximum of 17%. • The bulk of turbulence was produced close to the test models and transported away. • Similarity in symmetry suggests "pairing" of the 1st and 2nd POD modes. - Abstract: An experimental investigation of turbulent flow over complex two-dimensional bluff bodies using a particle image velocimetry (PIV) technique is reported. The study obtained extensive data sets and documented the salient features of these complex flows using the mean flow and turbulent quantities as well as proper orthogonal decomposition (POD) analysis. The results indicate that all the turbulent quantities increased with downstream distance and test model distance from the test section floor as well as cavity depth but no significant increase in turbulence with the cavity length. The triple velocity correlations indicate that there is negative transport of turbulence kinetic energy in the streamwise direction close to the test section floor but positive transport away. The bulk of turbulence was produced close to the test models and transported away. The POD modes with the same symmetry appeared to be similar in shape, but shifted in the streamwise direction. This similarity in symmetry suggests "pairing" between the first and second POD modes