The turbulent radial flow between parallel annular plates of finite span is studied with a focus on instabilities induced by a periodically modulated swirling source inflow. This investigation utilizes a combination of theoretical modeling along with simplified two- and three-dimensional numerical simulations. Different levels of complexity gradually evolve in the radial diffuser model to identify the different instabilities and to trace back the instabilities to different physical mechanisms. First, a linear stability analysis is performed for a two-dimensional core-flow instability mechanism on a one-dimensional basic state, considering the flow to be inviscid and homogeneous in the azimuthal $\theta$ direction. Following this, several two-dimensional numerical simulations are conducted, including viscous effects, nonlinear effects, and inflow modulation in the azimuthal direction. Finally, three-dimensional numerical simulations are carried out to evaluate the impact of the boundary layer on the instabilities.

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• Flow instability
• Rotating turbulence
• Wakes & jets