In the annular cascade test

we aim to observe the fluid field behind the annulus blades

focusing on the velocity field and the vortex shedding frequency in particular

and to investigate the effect of fluid incidence and flux on them.In comparison with the cascade with high positive incidene

the high negative incidence cascade has wider separating section

stronger vortex

and slower wake delay

but weaker vortex intensity.As the incidence approaches the designed value

it can be seen obviously that the separation diminishes and dissipates as the vortices quickly blend with the main flow. Additionally

there is a characteristic frequency valued at 723 Hz in the diverse cases.