POD analysis of a vortex rope with transient boundary conditions

The paper presents the results of a POD analysis of the flow in a swirl generator. The generator has two separate inlets - one straight axial inlet and one tangential inlet ended by a spiral case. This allows to set different operating points, which are in turn connected with different shapes of the vortex rope present in the flow field. In this case, the investigation is aimed at linearly varying flow rates at the boundaries, namely, the ratio of the tangential flow rate is increased from 40 % up to more than 80 % of the total flow rate, which is maintained constant. Substituting the POD modes into the energy equation provides additional insight into the energy fluxes between the modes and consequently into a major part of the turbulent flow energy cascade as the input data were gained from a CFD simulation using scale-resolving Stress-Blended Eddy Simulation model. The POD modes can be used to construct a simplified model of the vortex rope dynamics covering a wider operating range rather than just one point.