Date

2022-2-8

Author

çolak, ılgın

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Turbulence is an important phenomenon in aerospace sciences, but it still has aspects that are not fully illuminated. In order to understand the physical mechanisms of turbulence, it is crucial to consider it in terms of eddies. Eddies are the groups of fluid particles that move together and preserve a certain identity for a while, and they constitute the building blocks of turbulence. The motion of eddies in the course of their life span can be expressed as dispersive wave motion. This requires a dispersion relation, that is the frequency and the wavelength must be related by a quantity having the dimensions of velocity. The dispersion relation that is commonly used in literature is suggested by G.I Taylor based on his Frozen Turbulence hypothesis. However, it has certain limitations such that it represents only the universal equilibrium region of the spectrum to acceptable accuracy. Also, turbulence intensity must be low. Quantic Behavior of Turbulence (QBT), is suggested by Çıray\cite{Ciray_1980} as an alternative and it aims to represent the physics of turbulence more accurately and in a more universal manner without the aforementioned restrictions. Moreover, it asserts that turbulence has both particle and wave-like character, which is why it is called quantic. QBT introduces a new dispersion relation that relates wavenumber with frequency by means of group velocity, which is, at the same time fluctuating component of the instantaneous velocity. This thesis is based on QBT approach of Çıray. The aim of the study is to apply the mathematical consequences of QBT to different experimental data by utilizing a MATLAB code developed for this purpose and to analyze the results considering the physics of turbulence. Using the mathematical procedure of QBT, the code produces energy spectra on frequency out of the experimental data, and using that information obtains wavenumbers that correspond to the frequencies. In this study, two different turbulent flow data are examined. For both of them, spectra on wavenumber is obtained and comparison shows that they are compatible with the studies in the literature. Also, eddie sizes, which are obtained as wavelengths, are quite meaningful when the physical domains are considered. Thus, it is concluded that the QBT and its application in this thesis study can be very helpful to understand the physical mechanism of turbulence.

Subject Keywords

turbulence, convective velocity, dispersion relation, quantic behavior

URI

https://hdl.handle.net/11511/96696

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Graduate School of Natural and Applied Sciences, Thesis