For studying the structures of opposed mixing flow at the outlet of radial centripetal turbine

large eddy simulation was used to simulate the convective mixing flow of the circumferential intake. Flow structures in different modes were extracted and analyzed by the proper orthogonal decomposition (POD) method. The results showed that there existed stagnation zone near the bottom center and a recirculation zone near both sides of the wall

and the flow was approximately symmetrical at the horizontal cross section. The instability of the vortex structure was strengthened due to the effect of the shear force along the streamwise direction. Furthermore

the upstream three-dimensional vortex ring structure was stretched and expanded

breaking into a complex vortex braid or hairpin vortex structure

which enhanced the mixing

and also the momentum and energy exchanged between the fluids. The POD results showed that the first mode had the highest energy weight

indicating that most of the energy in the pulsating field was concentrated in this mode

and the flow structure in this mode acted as the main flow structure.