"Demonstration of wavelet techniques in the spectral analysis of bypass transition data"

Lewalle, J., Ashpis, D.E. and Sohn, H.-K.


We develop and illustrate a number of wavelet-based techniques for the analysis of experimental data. We used the data of Sohn & Reshotko (NASA CR 187068, 1991), which consists of simultaneous hot wire velocity traces in bypass boundary layer transition on a heated flat plate. Our purpose is to demonstrate that the results of multiscale analysis apply to the modeling of related industrial flows. From the dataset of Sohn & Reshotko, we excerpt a pair of traces (2 components of velocity) at one location, and we calculate a number of statistics related to dominant time scales for energy and for momentum transport, their quadrant distributions, and their intermittency. We find that energy-dominant time scales inside spots are poorly identified, whereas transport-dominant scales inside spots accouidentified, whereas transport-dominant scales inside spots account for the largest part of the Reynolds stress. We also observe that momentum transport is much more intermittent than energetic fluctuations, translating into very rare rare contributions to transport at between spots.

NASA TP # 3555, 1997.

Jacques Lewalle, jlewalle@syr.edu