Abstract:
Proper Orthogonal Decomposition (POD) is widely used in the field of Reduced Order Modeling (ROM). Based on a large data set of a turbulent flow, a few POD modes are sufficient to characterize the dynamics of the underlying flow. Instability waves that grow in turbulent shear layers are usually represented by two coupled POD modes. The corresponding Fourier coefficients can be  used to reconstruct the relative phase angle and to per-form a phase average. This method will be demonstrated for the turbulent swirling jet undergoing vortex breakdown. This particular flow configuration is dominated by strong helical instabilities located in the inner and outer shear layer of the swirling jet. The phase reconstruction based on an ensemble of PIV snapshots will give access to the radial amplitude function, the phase velocity and the spatial growth rate of the dominating instabilities.

More information: Prof. V. Tesař