Experimental investigation of a trench weir with T-shaped bars
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TECHNICAL PAPER
Experimental investigation of a trench weir with T‑shaped bars Swati Bhave1 · Sanjeev Kumar2 · Umesh K. Singh3 · Manish Pandey4 · Zulfequar Ahmad5 Received: 24 September 2018 / Accepted: 18 August 2020 / Published online: 23 September 2020 © The Brazilian Society of Mechanical Sciences and Engineering 2020
Abstract The most common type of diversion structure used in boulder streams is a trench weir. It is a simple structure built below the bed level of streams, and the top of it is covered with bottom rack. Bottom rack consists of bars of various shapes like circular, rectangle, T-shaped, etc. It is placed over the trench weir with a desired porosity to control sediment ingestion into trench. In this present study, T-shaped bars are used because sediment ingestion and maintenance in the bottom rack consisting of T-shaped bar shall likely too low as compared to the rounded bars and rectangular bars. As in previous studies, Garcia et al. (Water 10(1035):1–21, 2018a, Water 10(1699):1–21, 2018b) compared the blocking capacity of bottom intakes having circular bars with intakes having T-shaped bars, they claimed that circular bar is inefficient as compared to T-shaped bars. The present study is based on experimental investigation of trench weir consisting of T-shaped bars under free flow condition, and it was found that the coefficient of discharge decreases with an increase in clear spacing of rack, slope of bottom rack, specific energy of approach flow, Froude number and Reynolds number. An equation is also being proposed to calculate coefficient of discharge with a maximum error of ± 20%. Keywords Bottom rack · Diversion channel · Mountainous river · Sediments · Trench weir Abbreviations B Width of channel, m a1 − g1 Coefficients Cd Coefficient of discharge E0 Specific energy of approach flow, m Fr Froude number g Acceleration due to gravity, m/s2 L Length of bottom rack, m Lw Wetted length of bottom rack, m Technical Editor: Jader Barbosa Jr., Ph.D. * Swati Bhave [email protected] 1
Department of Civil Engineering, Visvesvaraya National Institute of Technology Nagpur, Nagpur, Maharashtra 440010, India
2
Department of Civil Engineering, Graphic Era University, Dehradun, Uttarakhand 248002, India
3
Department of Civil Engineering, Koneru Lakshmiah Education Foundation (Deemed to be University), Guntur, Andhra Pradesh 522502, India
4
Department of Civil Engineering, National Institute of Technology, Warangal, Telangana 506004, India
5
Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667, India
Qd Diverted discharge into channel, m3/s Qm Discharge in main channel, m3/s R Hydraulics radius, m Re Reynolds number S Upstream bed slope of main channel s Clear spacing of rack, m sr Rack slope t Thickness of rack, m V0 Approach velocity, m/s Vh Velocity head, m 2 Vh* Dimensionless velocity head, V0 2gE0
y0 Depth of flow in main channel upstream of rack, m ys Submergence depth, m yt Depth of flow in main channe
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