توسعه زمانی آب‌شستگی موضعی در پایین‌دست حوضچه آرامش با شیب معکوس

نویسندگان

چکیده

در این بررسی،‏ پیشرفت زمانی نیمرخ‌های حفره آب‌شستگی موضعی در پایاب حوضچه آرامش با شیب معکوس بر‌اساس نتایج برداشت نیمرخ‌های حفره در محدوده گسترده‌ای از اعداد فرود،‏ دانه‌بندی ذرات رسوبی،‏ عمق پایاب،‏ طول و شیب حوضچه بررسی شد. انجام یک آزمایش 54 ساعته نشان داد نزدیک به 5‎/87% از عمق بیشینه،‏ 3‎/86% از فاصله عمق بیشینه تا انتهای کف‌بند در پایان 54 ساعت آزمایش،‏ در مدت زمان 24 ساعت از شروع آزمایش به دست می‌آید. همچنین،‏ معادله توانی ارتباط دهنده عمق حفره با مقیاس زمانی و هندسه سازه بالادست ارائه و ضریب‌ها و توان‌های این معادله به‌صورت توابعی از شیب حوضچه درنظر گرفته شد. تأثیر پارامترهای مختلف بر ابعاد حفره بررسی و معادلاتی برای تخمین ابعاد حفره با زمان و در شرایط تعادل نسبی ارائه شد. برداشت نیمرخ‌های آب‌شستگی نشان دهنده وجود نوعی تشابه در شکل حفره در پایاب هر شیب است. همچنین نتایج نشان داد افزایش طول و شیب حوضچه معکوس سبب شکل‌گیری حفره‌ای با عمق کمتر و گستره طولی بیشتر می‌شود و حجم نسبی رسوبات انتقال یافته از واحد عرض حفره به ازای افزایش شیب حوضچه تا 15% در حدود 30% افزایش خواهد یافت.

کلیدواژه‌ها


عنوان مقاله [English]

Time-dependent local scour downstream of adverse stilling basin

نویسندگان [English]

  • Hossein Khalili Shayan
  • Javad Farhoudi
چکیده [English]

The paper describes the evolution of local scour hole downstream of an adverse stilling basin. The research was conducted using a wide range of the Froude number, sediment size, tailwater depth, length and slope of stilling basin. The results showed that 87.5% of maximum depth of scour and 86.3% of its distance from the stilling basin were occurred in the first 24 hours when the experiment was continued for 54 hours. A power equation was adopted to describe the characteristic dimensions of the scour-hole, time scale as well as the geometry of stilling basin and sluice gate. The effects of different parameters on the dimension of the scour-hole were investigated and some equations were presented for estimating the variation of scour-hole dimensions with time under relative equilibrium condition. The results also showed a certain similarity among the scour profiles developed at different times. However, the shape of the holes was influenced by the change in length and slope of stilling basin. As the slope of stilling basin increased by 15%, the volume of sediment removed from the unit width of the hole, was increased by 30%.
The paper describes the evolution of local scour hole downstream of an adverse stilling basin. The research was conducted using a wide range of the Froude number, sediment size, tailwater depth, length and slope of stilling basin. The results showed that 87.5% of maximum depth of scour and 86.3% of its distance from the stilling basin were occurred in the first 24 hours when the experiment was continued for 54 hours. A power equation was adopted to describe the characteristic dimensions of the scour-hole, time scale as well as the geometry of stilling basin and sluice gate. The effects of different parameters on the dimension of the scour-hole were investigated and some equations were presented for estimating the variation of scour-hole dimensions with time under relative equilibrium condition. The results also showed a certain similarity among the scour profiles developed at different times. However, the shape of the holes was influenced by the change in length and slope of stilling basin. As the slope of stilling basin increased by 15%, the volume of sediment removed from the unit width of the hole, was increased by 30%.
The paper describes the evolution of local scour hole downstream of an adverse stilling basin. The research was conducted using a wide range of the Froude number, sediment size, tailwater depth, length and slope of stilling basin. The results showed that 87.5% of maximum depth of scour and 86.3% of its distance from the stilling basin were occurred in the first 24 hours when the experiment was continued for 54 hours. A power equation was adopted to describe the characteristic dimensions of the scour-hole, time scale as well as the geometry of stilling basin and sluice gate. The effects of different parameters on the dimension of the scour-hole were investigated and some equations were presented for estimating the variation of scour-hole dimensions with time under relative equilibrium condition. The results also showed a certain similarity among the scour profiles developed at different times. However, the shape of the holes was influenced by the change in length and slope of stilling basin. As the slope of stilling basin increased by 15%, the volume of sediment removed from the unit width of the hole, was increased by 30%.
The paper describes the evolution of local scour hole downstream of an adverse stilling basin. The research was conducted using a wide range of the Froude number, sediment size, tailwater depth, length and slope of stilling basin. The results showed that 87.5% of maximum depth of scour and 86.3% of its distance from the stilling basin were occurred in the first 24 hours when the experiment was continued for 54 hours. A power equation was adopted to describe the characteristic dimensions of the scour-hole, time scale as well as the geometry of stilling basin and sluice gate. The effects of different parameters on the dimension of the scour-hole were investigated and some equations were presented for estimating the variation of scour-hole dimensions with time under relative equilibrium condition. The results also showed a certain similarity among the scour profiles developed at different times. However, the shape of the holes was influenced by the change in length and slope of stilling basin. As the slope of stilling basin increased by 15%, the volume of sediment removed from the unit width of the hole, was increased by 30%.

کلیدواژه‌ها [English]

  • Hydraulic jump-Scour profile-Sluice gate-Adverse stilling basin-Temporal dependence.-