Aerodynamic pressure measurements are usually
interpreted through statistical tools involving modal representations. The most
popular approach is based on the Principal Component Analysis (PCA), which
provides the theoretical basis of the well-known concept of coherent structure
is derived. In order to overcome theoretical and practical limitations of PCA, alternative
approaches can be formulated adapting techniques developed in the feature-recognition
field to the description of pressure fields. In this sense, the Independent
Component Analysis (ICA) can be conceived as an evolution of PCA in which
high-order statistics are used to identify statistical independent sources; ICA
has been used to solve the Blind Source Separation (BSS) problem as well as to
extract features from random data. Both PCA and ICA shows severe limitations
when applied to represent (and interpret) propagating phenomena such as the
pressure field due to a vortex shedding
and its advection by the mean flow. The explicit description of the time
evolution is introduced through two techniques presented herein, Dynamic-PCA
and Dynamic-ICA, and the novel concept of dynamic coherent structure is
presented. The application of the above-mentioned methods is demonstrated
referring to the aerodynamic pressure field measured on a bluff body immersed
in a turbulent boundary layer.
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