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    AEROACOUSTICS INVESTIGATIONS OF UNSTEADY 3D AIRFOIL FOR DIFFERENT TURBULENCE MODELS USING COMPUTATIONAL FLUID DYNAMICS SOFTWARE
    (Parlar Scientific Publications (P S P), 2019) Kepekci, Haydar; Zafer, Baha; Guven, Hasan Riza
    Noise formation is one of the most important factors taken into consideration in the studies conducted in aviation areas. This paper reviews the flow area studied on the 3D NACA0015 blade profile using different turbulence models as SST k-co, Smagorinsky-Lilly, WALE, and WMLES to calculate the unstable flow field. In addition, the effect of mesh number and time step on the results was analyzed by using CFD program. The mesh files used in the analysis are prepared with the Pointwise program. We inserted the time-dependent flow field variables in Ffowcs-Williams and Hawkings (FW-H) equations as an input and Sound Pressure Level (SPL) values will be computed for different turbulence models from the microphone which is positioned in the computational domain to investigate the effect of augmentation of unsteady 3D airfoil region noise level. The calculated results will be compared with each other and with the experimental data available in the open literature. In the analysis, the Sound Pressure Level (SPL) effect of mesh number was investigated by using different 3 mesh numbers being 2 million, 3 million, and 4 million. In addition, to analyze the effect of the time step on the Sound Pressure Level (SPL), analyzes were made using 2 different time steps being 10(-4) and 10(-5); and the results were compared with each other. As results; calculated Cp values are slightly lower than the experimental value. This difference could be due to the higher Reynolds number of the experimental data. The result obtained from the comparison of the different turbulence models used is the most suitable choice is Smagorinsky-Lilly model for the use of LES method in the study of the mean sound pressure related to the unsteady 3D airfoil. Also, the results obtained from the analysis with the increase in the number of mesh and the reduction of the time step were found to be closer to the experimental data.
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    Three-Dimensional Cfd Modeling Of Thermal Behavior Of A Disc Brake And Pad For An Automobile
    (Oxford University Press, 2020) Kosa, Ergin; Kepekci, Haydar; Ezgi, Cüneyt; Cihan, Ahmet
    The brake system of an automobile is composed of disc brake and pad which are co-working components in braking and accelerating. In the braking period, due to friction between the surface of the disc and pad, the thermal heat is generated. It should be avoided to reach elevated temperatures in disc and pad. It is focused on different disc materials that are gray cast iron and carbon ceramics, whereas pad is made up of a composite material. In this study, the CFD model of the brake system is analyzed to get a realistic approach in the amount of transferred heat. The amount of produced heat can be affected by some parameters such as velocity and friction coefficient. The results show that surface temperature for carbon-ceramic disc material can change between 290 and 650 K according to the friction coefficient and velocity in transient mode. Also, if the disc material gray cast iron is selected, it can change between 295 and 500 K. It is claimed that the amount of dissipated heat depends on the different heat transfer coefficient of gray cast iron and carbon ceramics.