Particle Image Velocimetry Measurements of Flow Over an Ogee-Type Weir in a Hydraulic Flume
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TECHNICAL NOTE
Particle Image Velocimetry Measurements of Flow Over an Ogee-Type Weir in a Hydraulic Flume Jarosław Biegowski1 • Maciej Paprota2
•
Wojciech Sulisz2
Received: 29 January 2020 / Revised: 8 June 2020 / Accepted: 10 June 2020 Ó The Author(s) 2020
Abstract Laboratory tests of water flowing over a modified ogee weir are carried out in a wave–current flume for two different scales. A model of a weir representing a part of a spillway section of the existing Włocławek dam (Vistula River, Poland) is mounted in a wave–current flume. The Froude similarity law is used to simulate the flow over a real damming structure at 1:25 and 1:50 scales. Particle image velocimetry methods are employed to measure a flow velocity field over the crest of the weir model. The system is capable of providing high fidelity velocity fields at sampling rates of 10 Hz and 50 Hz. Detailed information on flow characteristics is extracted from the instantaneous velocity field measurements to provide a comprehensive description of the kinematics of a weir flow at discharges corresponding to hydrological events with return periods of 100 and 1000 years, revealing some interesting spatial features. The geometry of the weir results in the development of a characteristic circulation cell, which is relatively wide for the lower discharge. When the flow intensity increases, a triangular circulation develops behind the weir crest instead. Moreover, sudden changes in the flow regime lead to the rapid formation of vortex structures, which propagate downstream at speeds ranging from 0.3 to 1 m s-1. The origin of eddy formation is identified at the upstream and downstream ends of the weir crest for respective average velocities at the crest of approx. 0.6 m s-1 and 1.2 m s-1. Keywords Weir flow Particle image velocimetry (PIV) Wave–current flume Vortex structure
1 Introduction Dam engineering structures are widely used to raise the water level and thus secure safe retention and storage of water for a number of fundamental purposes, such as navigation, irrigation, water supply, hydroelectricity, regulation of rivers, flood control, etc.[1]. Weirs constitute a
& Maciej Paprota [email protected] Jarosław Biegowski [email protected] Wojciech Sulisz [email protected] 1
Department of Coastal Engineering and Dynamics, Institute of Hydro-Engineering, Polish Academy of Sciences, Gdan´sk, Poland
2
Department of Wave Mechanics and Structural Dynamics, Institute of Hydro-Engineering, Polish Academy of Sciences, Gdan´sk, Poland
common type of hydraulic damming solutions that either form part of an embankment or a concrete dam, or are built as standalone structures. There is no universal type of a weir, as its configuration differs depending on the local requirements and technical capabilities. Weirs are constructed as sharp-crested and broad-crested structures. Sharp-crested weirs include rectangular, triangular, and trapezoidal notches. Broad-crested weirs are generally constructed as concret
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