Affiliations: Energy and Process Engineering, Tampere University of
Technology, PO Box 589, 33101 Tampere, Finland | Measurement and Information Technology, Tampere
University of Technology, PO Box 589, 33101 Tampere, Finland. e-mail: mika.
[email protected]
Abstract: A new method to apply spatial two-dimensional power spectral density
(2D PSD) analysis to the data measured with Particle Image Velocimetry (PIV)
has been introduced. Applying the method to a set of the velocity vector fields
characteristic turbulence length scales can be estimated. In this method the
computation of 2D PSD has been performed to two kinds of pre-processed data. In
the first set, the local average has been spatially subtracted (Spatial
decomposition) and in the second set the time-average has been subtracted
(Reynolds decomposition). In the computation of 2D PSD the 2D FFT with the
variance scaling has been used. Besides 2D spectral analysis this paper uses
the distribution analysis of the various turbulence quantities and a structure
analysis method to estimate the dimensions of coherent structures in the flow.
Another method to analyse turbulence length scales is the estimation of the
spatial 2D Auto Correlation Coefficient Function (2D ACCF). All these methods
applied side by side to the PIV data increase the understanding of the
turbulence, its scales and the nature of the coherent structures.