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ISSN: 2375-3846

American Journal of Science and Technology

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Frequency Prediction of a Von Karman Vortex Street Based on a Spectral Analysis Estimation

American Journal of Science and Technology
Vol.5 , No. 2, Publication Date: May 30, 2018, Page: 26-34

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Authors

[1]	Rafael Bardera-Mora, National Institute for Aerospace Technology (INTA), Torrejón de Ardoz, Spain.
[2]	Miguel Ángel Barcala-Montejano, Department of Aircraft and Space Vehicles, School of Aeronautics and Space Engineering, Universidad Politécnica de Madrid, Madrid, Spain.
[3]	Ángel Antonio Rodríguez-Sevillano, Department of Aircraft and Space Vehicles, School of Aeronautics and Space Engineering, Universidad Politécnica de Madrid, Madrid, Spain.
[4]	Miguel Ruiz de Sotto, Department of Aircraft and Space Vehicles, School of Aeronautics and Space Engineering, Universidad Politécnica de Madrid, Madrid, Spain.
[5]	Gonzalo González de Diego, Department of Aircraft and Space Vehicles, School of Aeronautics and Space Engineering, Universidad Politécnica de Madrid, Madrid, Spain.

Abstract

Spectral analysis studies the power distribution over frequency of a signal. This allows the characterization of time signals by its harmonics. This article will establish a relationship between the autocorrelation function and the spectrum. The direct implementation of the theory when analyzing a finite time signal results in a raw periodogram or first estimation of the spectrum. However, owing to the biased nature of the autocorrelation function, the periodogram obtained will not be a good estimation. Thus, several estimation techniques are needed in order to acquire a reliable spectrum. Amongst the techniques handled are the averaging Welch method, the use of window functions or tapering and the implementation of Fast Fourier Transform algorithms. To validate the accuracy and improvements made with these techniques, an algorithm is implemented in Matlab. Several synthetic signals are assessed and the classical Kármán Vortex Street is performed in a wind tunnel experiment. The results obtained are proof of the need for a careful study of the different estimation techniques when analyzing a signal.

Keywords

Spectral Analysis, Welch Averaging, Tapering, Resampling, Kármán Vortex Street

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