توصیف احتمالاتی انتقال بار بستر بعد از آستانه در یک بررسی آزمایشگاهی با استفاده از روش ردیابی سرعت ذره

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری سازه های آبی، گروه علوم و مهندسی آب، دانشگاه فردوسی مشهد

2 دانشیار گروه علوم و مهندسی آب ، دانشگاه فردوسی مشهد

3 استادیار/ دانشکده مهندسی عمران و محیط زیست، دانشگاه گلسگو، گلسگو، اسکاتلند

4 گروه مهندسی سازه‌های آبی، دانشکده آب و خاک، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گلستان، ایران

چکیده

حرکت رسوب با اهمیت فراوانی که در مهندسی و علم هیدرولیک دارد فیزیک کاملاً شناخته شده‌ای ندارد. نادیده گرفتن حرکت نوسانی و طبیعت ناپیوسته انتقال بار بستر، کاربرد روابطی که بر این اساس برای تخمین بار انتقال رسوب ارائه شده‌اند را دچار چالش کرده است. این پژوهش سعی دارد حرکت غیرمعلق (حرکت بار بستر) یک ذره با وزن‌های متفاوت را در شرایط مختلف جریان با استفاده از تکنیک‌های رهگیری ذره، مورد کاوش قرار دهد و آن را در قالب توابع توزیع احتمالاتی توصیف کند. با مشخص شدن رفتار آماری در رابطه با عامل یا عوامل مؤثر انتقال در رژیم‌های مختلف انتقال رسوب، می‌توان اظهار نظر دقیق‌تری داشت. در این راستا با استفاده از تکنیک رهگیری ذره (PTV)، موقعیت ذره در هر سری آزمایش مشخص شد. در نهایت با محاسبه سرعت لحظه‌ای ذره توابع توزیع احتمالاتی مختلف بر داده‌ها برازش داده شد تا بهترین تابع با توجه به معیار سنجش آماری کولموگروف-اسمیرنوف (در سطح اطمینان 5 درصد) انتخاب شود. نتایج نشان داد که انتقال ذره در اعداد رینولدز پایین جریان از تابع توزیع لوگ-نرمال و در اعداد رینولدز جریان بالا از تابع توزیع نرمال تبعیت می‌کند. همچنین به وسیله این مشاهدات در رابطه با عامل حرکت در شرایط مختلف رژیم انتقال رسوب بحث شد که با توجه به ویژگی‌های توابع توزیع احتمالاتی به دست آمده، انتقال رسوب در شرایط آستانه با عاملیت ارتباط ذره-بستر و در شرایط تعادلی تحت نیروهای سیال انجام می‌شود. در انتها با توجه به تفاوت رفتار حرکت رسوب در رژیم انتقال ضعیف و تعادلی می‌توان دو پارامتر آستانه معرفی کرد. با توجه به اهمیت کاربرد نتایج در مهندسی، به دلیل اینکه قالب پژوهش، قالب آماری و توصیف پدیده تصادفی بوده است می‌توان با در نظر گرفتن شرایط مختلف انتقال رسوب (با نمایندگی پارامتر عدد رینولدز ذره) احتمال وقوع سرعت ذرات را با استفاده از توابع توزیع ارائه شده، تخمین زد. همچنین نتایج این پژوهش در شرایط هیدرولیکی مشابه از جمله پژوهش‌های اکو-هیدرولیک و تونل باد قابل استفاده می‌باشد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Probabilistic description of coarse particle motion above threshold by particle tracking velocimetry method in an experimental study

نویسندگان [English]

  • Hamed Farhadi 1
  • kazem Esmaili 2
  • Manousos Valyrakis 3
  • Abdolreza Zahiri 4
1 Phd candidate for hydro structures, Water Science and Engineering Department, Ferdowsi University of Mashhad
2 Associate Professor Department of Water Science and Engineering , Ferdowsi University of Mashhad
3 Assistant professor/School of engineering, University of Glasgow, Glasgow, United Kingdom
4 Water and soil engineering faculty, Water engineering department, Gorgan university of agricultural sciences and natural resources, Gorgan, Iran
چکیده [English]

Sediment motion behavior plays an essential role in sediment and hydraulic engineering, though its physics is still not fully understood. Ignoring the stochastic nature of the sediment transport leads to various equations for bedload transport which are now being challenged due to their results. In this study, the non-suspended particle motion (bedload transport) in different hydraulic conditions was assessed by a particle tracking technique called Particle Tracking Velocimetry (PTV). The results of the PTV were applied to describe the particle behavior throughout the probability distribution functions. Knowing the particle motion behavior would guide learning more about the parameter/s governing the particle transport in different sediment transport regimes. The instantaneous particle velocity was measured after calibrating and validating the frames (resulted from the PTV). Different probability distribution functions were assessed with the Kolmogorov-Smirnov criterion (in 5 percent of the level of confidence) to find the best function which fits the collected data (i.e., the particle velocity). Furthermore, an analysis of the governing parameter for particle entrainment in different transport regimes was conducted. It was found that in a weak transport regime, the particle-bed and higher transport regime, the particle-flow interrelations were the governing factors that make the particle move. It was shown that the probability distribution function is Lognormal for lower particle Reynolds number, and on the other hand, in the higher particle Reynolds number, the Normal distribution best describes the particle velocity. The results of this research also could be applied in similar hydraulic conditions in the eco-hydraulic field, specifically macro-plastic movement as bedload in river courses and Aeolian research. 

کلیدواژه‌ها [English]

  • Bedload
  • Intermittent particle motion
  • Particle Tracking Velocimetry
  • Probability Distribution Function
  • Sediment transport

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نشریه مهندسی عمران امیرکبیر
دوره 54، شماره 4
تیر 1401
صفحه 1591-1606

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