3D circular cylinder

The main objective of the present study is to analyse the turbulence properties in unsteady, strongly detached flows and to provide a database for improvement and validation of turbulence models, concerning the present class of non-equilibrium flows. The flow around a circular cylinder with a low aspect ratio (L/D=4.8) and a high blockage coefficient (D/H=0.208) is investigated. This confined environment is used in order to allow direct comparisons with realisable 3D Navier-Stokes computations avoiding ‘infinite’ conditions. The flow is investigated in the critical regime at Reynolds number 140,000. A cartography of the velocity fields in the near wake of the cylinder is obtained by the 2D Particle Image Velocimetry. Statistical mean (Reynolds averaged) and phase-averaged quantities are determined. Furthermore, POD analysis is performed on the data set in order to extract coherent structures of the flow and to compare the results with those obtained by the conditional sampling technique. The Reynolds stresses, the strain-rate and vorticity fields as well as the turbulence production terms are determined. These physical quantities where not measured in this detail up to now, to our knowledge and they are very useful for the development of advanced turbulence modelling techniques for unsteady flows. Based on the IMFT’s circular cylinder test-case, computations are carried out by advanced statistical turbulence modelling and by DES. The partners involved are IMFT and STPU.