Investigation of the Link between Physics and POD Modes

摘要

The present study aims to clarify the link between vortical structures contained in instantaneous two-dimensional vector fields and their Proper Orthogonal modes. For this purpose, a set of synthetic images is decomposed and analyzed with the aid of a POD algorithm. It is shown that the higher intensity (vector length) of the modes is linked to the ensemble averaged kinetic energy of the corresponding vortices in the vector fields. This energy is correlated to the number of identical vortices in the initial synthetic data set. The algorithm is also applied on a data set obtained from measurements over a rectangular open cavity thanks to Particle Image Velocimetry (PIV). The vortical structures contained in this last flow are conjectured to be statistically equivalent to the leading POD modes of both the vector and the vorticity fields.