Air-water flow in bottom outlets

Speerli, Jürg; Hager, Willi H.

doi:10.1139/cjce-27-3-454

Cited by 6 publications

(4 citation statements)

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“…Harshbarger et al compared data obtained from a 1:20 scale gated structure model with field measurements [6]. In their study where they analyzed the air-water flow of the bottom outlets in the conduits, Speerli and Hager presented results showing the maximum air concentration and the development of these concentrations in terms of stream wise through the tunnel [7]. Unsal et al investigated the aeration performance of freesurface conduits [8].They emphasised that the free surface conduits were very effective for oxygen transfer in waters.…”

Section: Introductionmentioning

confidence: 99%

Estimating The Aeration Performance Of Venturi-Conduit By Artificial Bee Colony Programming

2022

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 Aeration performance of venturi-conduit was modeled by Artificial Bee Colony Programming.  Functions that can model aeration performance are defined for 2 different contraction ratios, 0.75 and 0.90.  Defined functions can predict the ventilation performance of conduits with venture-conduit without the need to build an experimental setup. Using these functions, the outputs (aeration performance) of different input values (Reynold, beta and length) can be calculated without the need for a training step.  The average RMSE value of the developed functions was measured as 1.64 for the contraction ratio 0.75, and 2.66 for 0.9.

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Section: Introductionmentioning

confidence: 99%

Estimating The Aeration Performance Of Venturi-Conduit By Artificial Bee Colony Programming

2022

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“…Experimental studies on air‐demand ratio and the oxygen transfer efficiency in closed conduits were carried out by investigators (e.g. Campbell & Guyton, 1953; Escarameia, 2007; Haindl & Sotornik, 1957; Kalinske & Robertson, 1943; Mahmoudi‐Rad & Najafzadeh, 2021; Mortensen, 2009; Mortensen et al, 2011, 2012; Oveson, 2008; Ozkan et al, 2006, 2014, 2015; Rajaratnam, 1962; Shamsaei & Soleymanzadeh, 2006; Sharma, 1976; Speerli, 1999; Speerli & Hager, 2000; Speerli & Volkart, 1997; Stahl & Hager, 1999; Tuna et al, 2014; Unsal et al, 2008, 2009; USACE, 1964; Wisner, 1965). The comprehensive literature search did not identify any published analytical or physical studies investigating the role of cross‐sectional geometry of high‐head gated conduit in oxygen transfer efficiency.…”

Section: Introductionmentioning

confidence: 99%

The role of cross‐sectional geometry of high‐head gated conduit in oxygen transfer efficiency

Baylar

Özkan

Yıldırım

et al. 2022

Water & Environment J

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The concentration of dissolved oxygen is an important indicator of water quality because aquatic life lives on the dissolved oxygen in the water. This can be achieved by using hydraulic structures because of substantial air bubble entrainment at these structures. Closed conduit aeration is a particular instance of this. In the present study, experiments were carried out to investigate the role of cross‐sectional geometry of high‐head gated conduit in oxygen transfer efficiency. In the first part of this study, the role of cross‐sectional geometry of high‐head gated conduit in air‐demand ratio was investigated. In the second part, the role of cross‐sectional geometry of high‐head gated conduit in oxygen transfer efficiency was investigated. Results pointed that the cross‐sectional geometry of the high‐head gated conduit had an important effect on the air‐demand ratio and the oxygen transfer efficiency. Moreover, a design formula was obtained for the conduit having the highest oxygen transfer efficiency relating the oxygen transfer efficiency to air‐demand ratio, Froude number, gate opening, conduit length and gate opening ratio. There was good agreement between the measured and the predicted values. The obtained results will be useful in future modelling processes and aid the practicing engineer in predicting oxygen transfer efficiency of high‐head gated conduits.

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“…Cavitation is one of the destructive phenomena that happen because of such negative pressure. Aeration by aerator tube is usually employed in order to control this phenomenon [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic Performance and Cavitation Analysis in Bottom Outlets of Dam Using CFD Modelling

Yamini

Mousavi

Kavianpour

et al. 2021

Advances in Civil Engineering

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Bottom outlets are significant structures of dams, which are responsible for controlling the flow rate, operation, or removal of reservoir sedimentation. The service gate controls the outlet flow rate, and whenever this gate is out of order, the emergency gate which is located at upstream is utilized. The cavitation phenomenon is one of the common bottom outlets’ problems due to the rapid flow transfer. The present research is a numerical study of the flow pattern in a dam’s bottom outlet for different gate openings by the use of Flow-3D software and RNG k-ε turbulence model. The investigation is carried out on the Sardab Dam, an earth dam in Isfahan (Iran). The maximum velocity for 100% opening of the gate and Howell Bunger valve is about 18 m/s in the section below the gate, and the maximum velocity for 40% opening of the gate is equal to 23.1 m/s. For 50% opening of the service and emergency gate in the valve’s upstream areas, the desired pressure values are reduced. Moreover, in the areas between the two emergency and service gates, the pressure values are reduced. The possibility of cavitation in this area can be reduced by installing aerators. The flow pattern in Sardab Dam’s bottom outlet has relatively stable and proper conditions, and there are no troublesome hydraulic phenomena such as local vortices, undesirable variations in pressure, and velocity in the tunnel, and there is no flow separation in the critical area of flow entering into the branch.

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Air-water flow in bottom outlets

Cited by 6 publications

References 0 publications

Estimating The Aeration Performance Of Venturi-Conduit By Artificial Bee Colony Programming

Estimating The Aeration Performance Of Venturi-Conduit By Artificial Bee Colony Programming

The role of cross‐sectional geometry of high‐head gated conduit in oxygen transfer efficiency

Hydrodynamic Performance and Cavitation Analysis in Bottom Outlets of Dam Using CFD Modelling

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