Extraction and analysis of turbulent large scales based on pod method

Proper orthogonal decomposition (POD) was used to deal with the databases obtained by direct numerical simulation in an orthogonally rotating turbulent duct flow. The turbulent large-scale structures and energy distribution in POD modes were extracted and analyzed. For every case studied, 200 turbulent instantaneous axial velocity snapshots with the same time interval were taken as samples. In order to investigate the influence of buoyancy on turbulent large-scale structures and the energy distributions in POD modes, four cases with different Grashof numbers were studied. The results show that the turbulent large-scale structures mainly locate in the unstable wall (y=0) and near the side walls; with the increase of the Grashof number, the most of the turbulent kinetic energy distributes into more POD modes.