Olivier Machiels

Experimental observation of flow characteristics over a Piano Key Weir

The Piano Key Weir is a type of labyrinth weir using overhangs to reduce the footprint of the foundation. These are directly placed on a dam crest. Together with its high discharge capacity for low heads, this geometry makes these weirs interesting in dam rehabilitation. However, the Piano Key Weir is a new weir type, first designed in 2001 and built from 2006 by Electricité de France. Even though experimental studies confirmed its appealing discharge capacities, the flow upstream, over and downstream of this complex structure is still not well known. This research presents experimental test results performed on a 1:10 scale model. The experiments aim at determining the flow features along the weir depending on the upstream head. The flow conditions are characterized in terms of specific discharge, velocity, pressure, water level and streamlines along the weir.

Experimental parametric study and design of Piano Key Weirs

ABSTRACT Piano Key Weirs are an effective solution for dam rehabilitation as well as new dam projects with a high level of hydraulic constraints. In order to improve the efficiency of their design, an experimental study of the influence of the main geometric parameters has been performed. Thirty one configurations were tested for a wide range of discharges. The results of the study show the influence of the weir height, the keys widths and the overhangs lengths on the discharge capacity and flow characteristics. Based on hydraulic considerations, optimum values of the main geometric ratios are provided. An analytical formulation is developed to predict the discharge capacity of the weir as a function of its geometry. It shows an accuracy of 10% compared to the experimental results of this study and from other sources.

Discharge coefficient for free and submerged flow over Piano Key weirs

The Authors made an interesting contribution to the assess-ment of the discharge coefficient of Piano Key weirs (PKW).The Discussers were impressed to read that the Authors con-ductedsome600teststherebyproducingnearly3000datapoints.Such systematic test series are helpful for a general descrip-tion of the PKW discharge capacity. Similar investigations arepresently conducted at several institutions. The Discussers vali-dated the Authors’ Eq. (6) with their own physical model data.Furthermore, the application limits of the tests performed bythe Authors are discussed with regard to the characteristics ofexisting prototype PKWs.The Laboratory of Engineering Hydraulics, Universite deLiege (ULG) and the Laboratory of Hydraulic Constructions,Ecole Polytechnique Federale de Lausanne (EPFL) have inde-pendently conducted research projects focused on the hydraulicefficiency of PKWs (Machiels 2012, Leite Ribeiro

Closure to “Parapet Wall Effect on Piano Key Weir Efficiency” by O. Machiels, S. Erpicum, P. Archambeau, B. Dewals, and M. Pirotton

Sebastien Erpicum, Ph.D.; Olivier Machiels, Ph.D.; Michel Pirotton, Ph.D.; Pierre Archambeau, Ph.D.; and Benjamin Dewals, Ph.D. Research Associate, Hydraulics in Environmental and Civil Engineering (HECE), Univ. of Liege (ULg), B-4000 Liege, Belgium (corresponding author). E-mail: s.erpicum@ulg.ac.be Project Engineer, Arcadis Belgium, B-4000 Liege, Belgium. E-mail: O.Machiels@arcadisbelgium.be Professor, Hydraulics in Environmental and Civil Engineering (HECE), Univ. of Liege (ULg), B-4000 Liege, Belgium. Research Associate, Hydraulics in Environmental and Civil Engineering (HECE), Univ. of Liege (ULg), B-4000 Liege, Belgium. Assistant Professor, Hydraulics in Environmental and Civil Engineering (HECE), Univ. of Liege (ULg), B-4000 Liege, Belgium.

Continuous formulation for bottom friction in free surface flows modelling.

Bottom friction modelling is an important step in river flows computation with 1D or 2D solvers. It is usually performed using empirical laws established for uniform flow conditions or a modern approach based on turbulence analysis. Following the definition of the flow validity field of the main friction laws proposed in the literature, an original continuous formulation has been developed. It is suited to model river flows with a wide range of properties (water depth, discharge, roughness...). The efficiency of this new formulation, theoretically established and numerically adjusted, is demonstrated through various practical applications.