نوع مقاله : مقاله پژوهشی
نویسندگان
1 دانشکده مهندسی مکانیک - دانشگاه یزد.
2 دانشکده مهندسی مکانیک - دانشگاه صنعتی اصفهان
3 مجتمع دانشگاهی مکانیک - دانشگاه صنعتی مالک اشتر
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
A turbulent flow over a finite height square cylinder placed vertically on a wind tunnel floor is experimentally investigated. All experiments were conducted with a single-component hot-wire anemometry in an open subsonic wind tunnel. The test section of the wind tunnel has a cross section of 457mm*457mm and a length of 1200 mm. The square cylinder has a side of 15mm and its aspect ratio is selected as 3 and 7. The model was mounted on the wind tunnel floor and its blockage ratio is 3.3 %. The model was placed 550 mm downstream from the entrance of the test section. The Reynolds number based on the cylinder side and inlet velocity is selected between 11000 to 22000 (free stream velocity is chosen between 11-22 m/s). The maximum turbulence intensity of flow in the wind tunnel is less than 0.2 %. Significant flow parameters, such as mean and rms velocity, dissipation rate, Kolmogorov length scale, frequency analysis and Strouhal number, are measured and calculated for different Reynolds numbers. The formation of the different types of vortices around the cylinder is observed by measurements of the present study. For example, it is observed that a vortex forms in the upstream of the cylinder close to the junction of the model and wall. Researchers also reported occurrence of this type of vortex for different geometries. The results indicate that the
variation of Strouhal number is independent of the Reynolds numbers considered and is, approximately, equal to 0.11. The results also show that the energy dissipation rate varies directly with the turbulence intensity, while it varies
indirectly with the Kolmogorov length scale. The experimental results are compared with the available data of the researchers and a reasonable agreement is observed. Furthermore, an accurate uncertainty analysis is applied to
determine the errors in the obtained experimental results. The maximum errors for instantaneous velocity and turbulence intensity are found equal to 7 % and 12%, respectively.
کلیدواژهها [English]
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