Investigating image velocimetry by spectrum analysis
Date Issued
2015
Date
2015
Author(s)
Cheng, Kai-Yin
Abstract
In recent years, debris-flow hazards occur frequently in Taiwan and cause casualties and property loss in many residential areas. In order to minimize the effect of such hazard, it requires more understanding of debris-flow’s behavior. The research is aim to develop an innovative image velocimetry, using spectrum analysis in the flow field. We took both celerity and water velocity into account to analyze the signal reflected from the water surface. After the images were transformed to gray level, the gray value represents the information of fluid motion. We first consider the spatial information of flow field as composite waveform and then transfer it to the frequency domain by using Fourier transformation. Afterwards, the dispersion relationship of wave theory was adopted to analyze the signal. For doing the velocity analysis, we first capture the signal of deep water wave and applied the inverse Fourier transformation to turn it into spatial domain. In this research, the issue existing in current image velocimetry that the flow field lacks of analyzable particle can be improved. However, there is still a room for waveform identification. The average error is 26% comparing to the results obtained via the instrument.
Subjects
image processing
signal processing
Fourier transform
spectrum analysis
Type
thesis
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