نوع مقاله : پژوهشی
نویسندگان
1 دانشکده فنی و مهندسی - دانشگاه خوارزمی
2 پژوهشکده مهندسی آب و دانشکده ی مهندسی عمران و محیط زیست- دانشگاه تربیت مدرس
3 دانشکده مهندسی عمران و محیط زیست- دانشگاه تربیت مدرس
چکیده
کلیدواژه‌ها
عنوان مقاله [English]
نویسندگان [English]
Spur dikes deflect the approaching flow to the far bank and decreases the sediment deposition. The scour hole formation and flow field features around spur dikes are interesting subjects in hydraulic engineering. In this paper, the flow field around straight spur dikes in a 90\u{1d52} sharp bend was investigated experimentally. Three different experiments were conducted in a prismatic channel with 90\u{1d52} bend at Tarbiat Modares University Tehran, Iran. In each experiment, a straight spur dike was attached to the outer bank in different angles with respect to the beginning of the bend. The flow fields were measured using Vectrino apparatus. In each point, the velocity was measured in 100 HZ frequency for 3 min. Despiking process was done using previous research approach. The spectral analysis, mean flow analysis, higher correlation analysis, bed shear analysis, turbulent intensity analysis, power spectrum analysis, and quadrant analysis were conducted. Results confirm the existence of the secondary flow in the bend, horse shoe vortex, and recirculation flow region. There is no strong difference between the mean flow fields around the spur dikes. Ejection and sweep events have the main role in shear layer regions, and the interactions are the dominant processes in the downstream recirculation zone. The spectral analysis confirms the existence of the inertial subrange for some frequency range. Some peaks are observed in power spectrum graphs that may, due to the vortex shedding process, confirm the ability of the flow for sediment transport. The bed shear stress based on linear relationship between bed shear stress and turbulent kinetic energy and bed shear stress and vertical velocity fluctuation in vertical direction cannot predict the scour potential region accurately. In addition, the contribution of the ejection events in Reynolds stresses may be one of the important reasons in sediment suspension in the initial time of scour process.
کلیدواژه‌ها [English]
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