A comparison of two analytical techniques for observing the energy spectra of a boundary layer was conducted to determine their effectiveness. The techniques used were power spectral density (PSD) and wavelet power spectrum (WPS) analyses. The types of trips include a 3 mm and 5 mm circular protuberance, a 5 mm square protuberance, and fine and rough sandpaper. The boundary layer profiles were acquired using hot-wire anemometry at various plate locations and wall heights. Original data was obtained for two distinct free-stream velocities across three distinct downstream locations and at several wall heights of y~+ = 5, 50 and 150. PSD and WPS plots were generated for a free-stream velocity of U_∞ = 13.5 m/s, at a downstream location 844 mm from the leading edge of the flat plate test rig. The PSD was generated using a Fast-Fourier Transform while the WPS used a numerically computed Continuous Wavelet Transform with the Morse wavelet applied to the transform. The results indicate that the PSD and WPS analyses support each other as their energy curves generally behave in the same manner. Characteristics of the WPS energy curves in the higher wavenumber region appear to have more distinct structure. This seems to imply a more accurate representation of the energy spectrum as a smoothing function was used on the PSD plots to reduce signal noise, and no such smoothing function was used on the WPS. The WPS energy spectra produced turbulence intensity values which are closer to the true value when compared to PSD for corresponding tripping conditions. This also supports the use of WPS over PSD for characterising the turbulent boundary layer as it shows WPS is more effective at representing the physical characteristics of the boundary layer. It is believed these distinct high wavenumber structures can be linked to the coherent structures present in the near wall region of the turbulent boundary layer.
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