نوع مقاله : پژوهشی
نویسندگان
1 دانشکدهی فنی و مهندسی، گروه مهندسی عمران، دانشگاه قم
2 پژوهشکده ی مهندسی مکانیک،سازمان پژوهش های علمی و صنعتی ایران. تهران
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
In this study the fluctuating loads of the control gate in the experimental model of the bottom outlet of a dam was evaluated. The production, transportation, and dissipation of turbulent flow eddies based on Kolmogorov theory were investigated by image processing of the flow under the control gate, time series of velocity and static pressure fluctuations. According to the results: 1- the flow turbulence at 10% opening of the control gate can be related to large eddies of middle and lower half streamlines of the upstream conduit. 2- The flow turbulence at 30% opening of the control gate can be related to large eddies of lower half streamlines of the upstream conduit. 3- The flow turned turbulent at 50% and 70% opening of the control gate can be related to large eddies of upper half streamlines of the upstream conduit. It can be concluded that the middle and lower streamlines of the upstream conduit play a major role in eddies production and flow turbulence at smaller openings of the control gate. In contrast, the upper streamlines of the upstream conduit play a major role in eddies production and flow turbulence at larger openings of the control gate. Large eddies are produced by shear layers created by velocity gradient at the guide slots of gate. The large eddies are transported by side guide slots toward the gate create strong secondary flows. After the collision of strong secondary flows with the main flow, the resulting turbulence leads to fluctuating static pressures. These fluctuations lead to the fluctuating loads on the control gate. Wavelet analysis of the time series provides the magnitude and frequency of pressure waves. Then, wavelet analysis and imaging of the gate flow reveal the causes of the turbulent flow formation process. The size and frequency of these large eddies range from 7.5 mm to 25 mm and 0.1 Hz to 2 Hz, respectively.
کلیدواژهها [English]
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