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Experimental and Numerical Study of Discharge Capacity and Sediment Profile Upstream of Piano Key Weirs with Different Plan Geometries

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Abstract

Piano key weirs (PKWs) are an improved form of labyrinth weirs, which are becoming popular as a more hydraulically efficient and cost-effective type of weir over its counterparts for both spillway and river flow conditions. More than thirty PKWs are already in construction worldwide, with constructions in India at Swara Kuddu. More than twenty parameters influence the flow over a PKW, and as such, the flow hydraulics near PKW is complex. It is imperative to study the performance of different shapes of PKW to know which shape offers more hydraulically and cost-effective advantages over other shapes. The present study combines the experimental and numerical study of discharge capacity and sediment carrying capacity of the different plan geometries of PKW. The experimental study of the discharging capacity of PKW has been carried out at eighteen discharge points for three plan geometries of PKW. A numerical study using ANSYS FLUENT has also been carried out at five discharges and compared with the experimental results. Vertical velocity near a weir is an essential factor facilitating the uplift of sediment. Sediment profile in the channel has been studied at three discharges experimentally for two types of PKWs: RPKW and TPKW6, all for free-flow conditions. The numerical study has also been carried out at these experimental discharges for studying the vertical component of velocity (v) upstream of PKW. An attempt has been made to isolate critical areas where the sediments are being lifted by the turbulence mechanism, thus helping them pass over the weir. The study shows PKW with a rectangular plan (RPKW) to be more hydraulically efficient than TPKWs with six-degree and thirteen-degree lateral crest variations (TPKW6 & TPKW13). The study also shows RPKW to be more self-cleaning in nature than its trapezoidal counterpart (TPKW6). Numerical study shows a close resemblance to the experimental results with errors well within permissible limits implying its greater use in ascertaining complex flows around hydraulic structures.

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Data Availability

Some or all data, models, or codes that support the findings of this study are available from the corresponding author upon reasonable request. All data, models, and code generated or used during the study appear in the submitted article.

Code Availability

ANSYS-FLUENT has been used for this study, license of which is available at IIT (BHU),Varanasi.

Abbreviations

PKW:

Piano Key Weir

RPKW:

Piano Key Weir with a rectangular plan

TPKW6, TPKW13:

Piano Key Weir with trapezoidal plan and α = 6 & 13 degrees

Relative ratio (r):

Increased discharge ratio (QPKW/QW)

Bi/ Bo :

Length of inlet/outlet cantilever overhang

Bb :

Base length

Ts :

Sidewall thickness

d:

Sand grain diameter (mm)

g:

Acceleration of gravity (m2 = s)

H:

Water head at sufficient distance upstream of PKW (upstream flow depth measured relative to the weir crest) (m)

h:

Water head at middle of the lateral crest of PKW (m)

L:

Total length of the PKW’s spillway front (developed crest length) (m)

P:

Vertical height of PKW (m)

Pi:

Height of inlet of PKW(m)

Q:

Discharge (L/S)

Cd :

Coefficient of discharge

Re:

Reynolds number

V:

Velocity (m/s)

v:

Velocity Component of Velocity(V) along vertical direction (Y) (m/s)

W:

Total width of the weir/channel (m)

We :

Weber number

Wi/Wo :

Inlet/outlet key width ratio

X:

Coordinate along flow direction (m)

Y:

Coordinate in the direction of the vertical depth (m)

Z:

Coordinate along transverse direction (m)

α:

Angle between the lateral crest and the longitudinal direction in the direction of flow (degrees)

B:

Upstream–downstream lateral crest length of PKW

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Acknowledgments

We acknowledge IIT (BHU), Varanasi for infrastructure support, and Main Library IIT (BHU), Varanasi, for paper downloads. We are also thankful to Dr. Bhawana Arora (Assistant Professor (English), Department of applied sciences, REC Sonbhadra, for taking out her precious time in language editing my paper.

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Authors and Affiliations

  1. Department of Civil Engineering, Indian Institute of Technology (BHU), Varanasi, 221005, India

    Amiya Abhash & K. K. Pandey

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  1. Amiya Abhash
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  2. K. K. Pandey
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Contributions

1. Amiya Abhash (Corresponding Author)

Conceptualization; Data curation; Formal analysis; Methodology; Investigation; Validation; Resources; Visualization; Software; Validation; Roles/Writing—original draft; Writing—review & editing.

2. Dr. K.KPandey (Author 2)

Conceptualization; Visualization; Methodology; Investigation; Resources; Supervision; Validation; Writing—review & editing.

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Correspondence to Amiya Abhash.

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Abhash, A., Pandey, K.K. Experimental and Numerical Study of Discharge Capacity and Sediment Profile Upstream of Piano Key Weirs with Different Plan Geometries. Water Resour Manage 35, 1529–1546 (2021). https://doi.org/10.1007/s11269-021-02800-y

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