Numerical Simulation and Proper Orthogonal Decomposition of the Flow in a Counter-Flow T-Junction

Large eddy simulations (LES) of the turbulent mixing in a T-junction have been carried out with the spectral element code Nek5000 at two inlet velocity ratios. Numerical results have been compared with an available experiment. Proper orthogonal decomposition (POD) has then been used to identify the most energetic modes of turbulence for both the velocity and temperature fields. Since POD was also performed on the experiment particle image velocimetry (PIV) data, a further means of verification and validation was available. The structure of the numerical POD modes and the time histories of the projection of each mode on the velocity field offer additional insight into the physics of turbulence in T-junctions. In particular, in the case of identical inlet velocities (T-junction velocity ratio equal to 1.0) the dynamics appears to be richer than might be expected and additional diagonal modes are present.