Effects of step pool porosity upon flow aeration and energy dissipation on pooled stepped spillways

AbstractThe hydraulics of stepped spillways with flat steps has been studied for the last three decades, including for embankment dam slopes, but studies of alternative stepped designs are limited. In this study, a pooled stepped spillway was investigated in a relatively large-size facility, and three different pool wall porosities were tested. The flow patterns, the macro- and microscopic air-water flow properties, and the energy dissipation performances were recorded; the results were compared with the flat stepped spillway design for the same chute slope (θ=26.6°). The investigations highlighted a close agreement between air-water flow properties on the configurations in terms of void fraction, turbulence levels, bubble count rate, and chord sizes. The interfacial velocity distributions showed larger interfacial velocity on the pooled step configurations of approximately 5–10% linked with a reduced flow depth. On the porous pooled stepped spillways, the interfacial velocities within the cavity highligh...

[1]  Hubert Chanson,et al.  Free-Surface Profiles, Velocity and Pressure Distributions on a Broad-Crested Weir: A Physical Study , 2012 .

[2]  L Peyras,et al.  Flow and Energy Dissipation Over Stepped Gabion Weirs , 1992 .

[3]  António N. Pinheiro,et al.  Inception Point and Air Concentration in Flows on Stepped Chutes Lined with Wedge-Shaped Concrete Blocks , 2008 .

[4]  Nallamuthu Rajaratnam,et al.  Characteristics of Skimming Flow over Stepped Spillways , 2000 .

[5]  Makoto Yamamoto,et al.  Visualization and laser measurements on the flow field and sand movement on sand dunes with porous fences , 2012 .

[6]  Hubert Chanson,et al.  Flow Resistance in Skimming Flows and its Modelling , 2002 .

[7]  Stefan Felder,et al.  Air-water flow properties on stepped spillways for embankment dams: Aeration, energy dissipation and turbulence on uniform, non-uniform and pooled stepped chutes , 2013 .

[8]  Hubert Chanson,et al.  Turbulence and cavity recirculation in air–water skimming flows , 2008 .

[9]  O. G. Martynenko,et al.  Handbook of hydraulic resistance , 1986 .

[10]  Yukio Ishida,et al.  Flow‐Induced Vibrations , 2012 .

[11]  N. Rajaratnam,et al.  Skimming Flow in Stepped Spillways , 1990 .

[12]  Hubert Chanson,et al.  Hydraulics of skimming flows over stepped channels and spillways , 1994 .

[13]  C. Wood,et al.  The Effect of Base Bleed on a Periodic Wake , 1964, Journal of the Royal Aeronautical Society.

[14]  Masayuki Takahashi,et al.  Flow Characteristics of Skimming Flows in Stepped Channels , 2004 .

[15]  Lena Osterhagen,et al.  Flow Induced Vibrations An Engineering Guide , 2016 .

[16]  F. Henderson.  Open channel flow , 1966 .

[17]  Hubert Chanson,et al.  Air Bubble Entrainment in Free-Surface Turbulent Shear Flows , 1996 .

[18]  Hubert Chanson,et al.  Air–water flows down stepped chutes: turbulence and flow structure observations , 2002 .

[19]  Hubert Chanson,et al.  Experimental Investigations of Free-Surface Aeration in the Developing Flow of Two-Dimensional Water Jets , 1998 .

[20]  Hubert Chanson,et al.  Air–water flow measurements in a flat slope pooled stepped waterway , 2013 .

[21]  Mehmet Ali Kökpinar.  Flow over a stepped chute with and without macro-roughness elements , 2004 .

[22]  Hubert Chanson,et al.  Flow aeration, cavity processes and energy dissipation on flat and pooled stepped spillways for embankments , 2013, Environmental Fluid Mechanics.

[23]  Hubert Chanson,et al.  Turbulence, dynamic similarity and scale effects in high-velocity free-surface flows above a stepped chute , 2009 .

[24]  Iwao Ohtsu,et al.  Developing flow in skimming flow regime on embankment stepped spillways , 2012 .

[25]  D. Bung.  Developing flow in skimming flow regime on embankment stepped spillways , 2011 .

[26]  Hubert Chanson,et al.  Energy dissipation, flow resistance and gas-liquid interfacial area in skimming flows on moderate-slope stepped spillways , 2009 .

[27]  Hubert Chanson,et al.  Energy Dissipation down a Stepped Spillway with Nonuniform Step Heights , 2011 .

[28]  Willi H. Hager,et al.  Two-Phase Flow Characteristics of Stepped Spillways , 2003 .

[29]  Luke Toombes,et al.  Experimental Study of Air-Water Flow Properties on Low-Gradient Stepped Cascades , 2002 .

[30]  G. K. Suryanarayana,et al.  Bluff-body drag reduction by passive ventilation , 1993 .

[31]  Hubert Chanson,et al.  Hydraulics of Stepped Chutes and Spillways , 2002 .

[32]  Hubert Chanson,et al.  Hydraulic Design of Stepped Spillways and Downstream Energy Dissipators , 2007 .

[33]  Hubert Chanson,et al.  Aeration, Flow Instabilities, and Residual Energy on Pooled Stepped Spillways of Embankment Dams , 2013 .

[34]  Anton Schleiss,et al.  High velocity aerated flows on stepped chutes with macro-roughness elements , 2004 .

[35]  Anton Schleiss.  Turbulence and cavity recirculation in air–water skimming flows on a stepped spillway , 2009 .