Experimental and Numerical Investigations of a Turbulent Flow Behaviours in Isolated and Non Isolated Conical Diffusers

This work presents an experimental and numerical investigation of a confined turbulent flow behavior across a conical diffuser (2α = 16°). The role of a perturbation caused by the presence of an elbow in the test-section, upstream of the progressive enlargement, was studied. The main measurements were the static pressure, and the instantaneous velocity fields using the Particle Image Velocimetry (PIV). Post-processing of these PIV measurements were adopted using the Γ₂ criterion for the vortices detection, and the Proper Orthogonal Decomposition (POD) technique to extract the most energetic modes contained in the turbulent flow and to the turbulent flow filtering. A data base has been also constituted, and was used to test the validity of the most models of turbulence, and in particular, a variant of the SST model.