Analysis and low order modeling of the inhomogeneous transitional flow inside a T-mixer

A direct numerical simulation of the transitional flow (Re=300 to Re=700) inside a T-mixer configuration has been carried out. Time records were collected and used to perform a proper orthogonal decomposition (POD) of the flow. Changes of the flow characteristics in the frequency spectra and extracted coherent spatial structures indicate flow transition across the investigated Reynolds numbers. The POD modes were used to derive a low-order model of the flow. An a priori test limits the possibilities of the modeling; for the periodic case it demonstrates that the flow can be reduced to a system of a few degrees of freedom, while for the turbulent ones this results to be extremely difficult because of the large number of degrees of freedom that are necessary to describe the flow.