In order to reveal the stratified flow characteristics of the viscous bottom layer and logarithmic layer in turbulent boundary layer of the hub endwall of turbine cascades

numerical simulation on the cascade flow field was carried out by using the ANSYS CFX software

based on the Reynolds time averaging Navie-Stokes equations and SST Turbulence model

taking the supercritical carbon dioxide turbine high-pressure static cascade as the study object. Moreover

the flow spectrum analysis and streamwise vorticity analysis were applied to further study the details of endwall boundary layer flow on different axial and circumferential sections

and the mechanism of stratified flow of viscous layer fluid and logarithmic layer fluid in cascades was revealed. The results show that

there are obvious differences in the flow spectrum of the rotating planes at different radial heights in the small area near the hub endwall of the supercritical carbon dioxide stator cascade. The differences indicate that the streamlines of the viscous layer

the logarithmic layer and the mainstream fluid near the hub endwall in the turbine cascades are different

which is stratified flow phenomena in the endwall boundary layer of the cascades. It is found that the opposite streamwise vorticity is obtained by the viscous layer fluid and logarithmic layer fluid when they are passing through the cascades

which eventually leads to the formation of turbine vortex system.