Date

2021-8

Author

Bekoğlu, Elif

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The knowledge of the energy contents, sizes, and lifetimes of eddies is necessary to understand the structure of turbulent flows. The spectral approach can provide the frequency-dependent energy spectrum, which helps to find out this structure. The present study focuses on finding eddy sizes or wavelengths using the frequency-dependent energy spectrum, which is consistent with the physics of turbulence. This is because the eddy size is related to wavenumber. The turbulence studies in the literature use a dispersion relation that connects frequency to wavenumber. The mentioned dispersion relation is generally used based on Taylor’s hypothesis, and examples of this usage are frequently encountered in the literature. Nevertheless, this approach has some deficiencies and limitations. As a result of this, several studies in the literature have tested and made corrections to this hypothesis. Some of them have tried to find alternative methods. The present thesis study includes the application of an alternative approach named Quantic Behavior of Turbulence (QBT) proposed by Çıray. With this approach, the nature of turbulence is explained with a dual character, including particle and wavy character. The mathematical procedure offered by this approach finds wavenumber to corresponding frequency. Within this study, the first step has been an implementation of this method to a Matlab code. This computer code uses the spectral approach to obtain the spectrum in the frequency domain. After that, the wavenumbers are provided by pursuing the mathematical procedure of QBT. Then, several different types of turbulent flows have been analyzed by this code. As a consequence of these analyses, the spectrum in the wavenumber domain is obtained in accordance with the data from the literature. With this approach, results such as sizes, lifespans, and energy contents of eddies are calculated in conformity with physical behavior. It is aimed that this approach and this study can contribute to more accurate understandings and solutions of turbulence problems.

Subject Keywords

the physics of turbulence, length scales, eddy sizes, energy spectrum

URI

https://hdl.handle.net/11511/92156

Collections

Graduate School of Natural and Applied Sciences, Thesis