Proper orthogonal decomposition analysis of coherent motions in a turbulent annular jet

doi:10.1007/s10483-021-2764-8

摘要/Abstract

摘要： A three-dimensional incompressible annular jet is simulated by the large eddy simulation (LES) method at a Reynolds number Re=8 500. The time-averaged velocity field shows an asymmetric wake behind the central bluff-body although the flow geometry is symmetric. The proper orthogonal decomposition (POD) analysis of the velocity fluctuation vectors is conducted to study the flow dynamics of the wake flow. The distribution of turbulent kinetic energy across the three-dimensional POD modes shows that the first four eigenmodes each capture more than 1% of the turbulent kinetic energy, and hence their impact on the wake dynamics is studied. The results demonstrate that the asymmetric mean flow in the near-field of the annular jet is related to the first two POD modes which correspond to a radial shift of the stagnation point. The modes 3 and 4 involve the stretching or squeezing effects of the recirculation region in the radial direction. In addition, the spatial structure of these four POD eigenmodes also shows the counter-rotating vortices in the streamwise direction downstream of the flow reversal region.

关键词: coherent structure, proper orthogonal decomposition (POD), turbulent annular jet, large eddy simulation (LES)

Abstract: A three-dimensional incompressible annular jet is simulated by the large eddy simulation (LES) method at a Reynolds number Re=8 500. The time-averaged velocity field shows an asymmetric wake behind the central bluff-body although the flow geometry is symmetric. The proper orthogonal decomposition (POD) analysis of the velocity fluctuation vectors is conducted to study the flow dynamics of the wake flow. The distribution of turbulent kinetic energy across the three-dimensional POD modes shows that the first four eigenmodes each capture more than 1% of the turbulent kinetic energy, and hence their impact on the wake dynamics is studied. The results demonstrate that the asymmetric mean flow in the near-field of the annular jet is related to the first two POD modes which correspond to a radial shift of the stagnation point. The modes 3 and 4 involve the stretching or squeezing effects of the recirculation region in the radial direction. In addition, the spatial structure of these four POD eigenmodes also shows the counter-rotating vortices in the streamwise direction downstream of the flow reversal region.

Key words: coherent structure, proper orthogonal decomposition (POD), turbulent annular jet, large eddy simulation (LES)

中图分类号:

76F10

Y. ZHANG, M. VANIERSCHOT. Proper orthogonal decomposition analysis of coherent motions in a turbulent annular jet[J]. Applied Mathematics and Mechanics (English Edition), 2021, 42(9): 1297-1310.

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