Coherent and turbulent process analysis in the flow past a circular cylinder at high Reynolds number

With the aim of providing a database useful for validation and improvement of turbulence models for strongly detached flows, the flow past a circular cylinder at high Reynolds number has been experimentally studied using PIV, stereoscopic PIV and Time Resolved PIV in the very near wake. As the presence of coherent structures and their non linear interactions with the turbulent motion have to be taken into account in a model, a particular attention was paid to the decomposition of the flow into a coherent and a turbulent part. This was achieved using phase averaging and also using Proper Orthogonal Decomposition. In a precedent study, it was found that the POD coefficients could be used to define a phase angle representative of the vortex shedding, and that defining the phase angle from the POD coefficients may alleviate the overestimation of the turbulent stresses due to phase jitter between the trigger signal and the velocity, compared to a definition of the phase angle from a wall pressure time trace. In this paper two new complementary data sets, which are resolved in time and space, are analysed with the objectives of, first, providing an evaluation of the performed conditional averaging and, second, to achieve a more complete description of the flow. The main results presented here are issued from Time Resolved PIV measurements which were carried out in the near wake. Some results of a Detached Eddy Simulation which have been validated against experiment, are also used.