Air-water flow in bottom outlets

2000 ◽  
Vol 27 (3) ◽  
pp. 454-462 ◽  
Author(s):  
Jürg Speerli ◽  
Willi H Hager
Keyword(s):  
Water Flow ◽  
High Velocity ◽  
Flow Characteristics ◽  
Design Procedure ◽  
Air Entrainment ◽  
Design Guidelines ◽  
Air Concentration ◽  
Tunnel Length ◽  
Mixture Flow ◽  
Bottom Outlets

Bottom outlets involve high-velocity air-water flow. Depending on the tunnel length, both air entrainment and air detrainment processes are significant. These processes are evaluated using a hydraulic model consisting of a long rectangular tunnel with a bottom slope larger than the critical slope. Expressions are presented for the maximum air concentration and its streamwise development along the tunnel. A prediction of mixture flow depth along the tunnel is developed. Design guidelines are presented relating to the flow pattern required, the air supply system, and the downstream submergence. The effect of tunnel length on the development of mixture flow characteristics is also outlined. A typical example shows the design procedure for bottom outlets.Key words: air entrainment, air-water flow, high-velocity flow, tunnel flow.

scholarly journals Aeration and deaeration at bottom aeration devices on spillways

1994 ◽  
Vol 21 (3) ◽  
pp. 404-409 ◽  
Author(s):  
Hubert Chanson
Keyword(s):  
High Velocity ◽  
Flow Characteristics ◽  
Air Entrainment ◽  
Air Concentration ◽  
Concentration Data ◽  
Cavitation Damage ◽  
Downstream Flow ◽  
Bottom Outlets ◽  
The Impact ◽  
Impact Region

Aeration devices are introduced along chute spillways and at bottom outlets to prevent cavitation damage in high velocity flows. Bottom aerators are characterized by large quantities of air entrained along the jet interfaces and also by a strong deaeration process near the impact of the water jet with the spillway bottom. In this paper, the aeration and deaeration occurring respectively in the aeration region and in the impact region are reviewed. A reanalysis of air concentration data obtained on models provides information on the flow characteristics at the end of the impact region. These results enable an accurate initialization of the downstream flow calculations using the method developed by Chanson. Key words: bottom aeration devices, aerators, spillways, air entrainment, detrainment.

Flow over a stepped chute with and without macro-roughness elements

2004 ◽  
Vol 31 (5) ◽  
pp. 880-891 ◽  
Author(s):  
Mehmet Ali Kökpinar
Keyword(s):  
Water Flow ◽  
High Speed ◽  
Length Distribution ◽  
Air Entrainment ◽  
Air Concentration ◽  
Bubble Frequency ◽  
Two Phase ◽  
Air Bubble ◽  
Roughness Elements ◽  
Stepped Chute

High-speed two-phase flows over a 30° stepped flume were experimentally investigated using macro-roughness elements. The roughness elements included combinations of steps and horizontal strips. Local values of air concentration, air bubble frequency, and mean chord lengths were measured by a fiber-optical instrumentation system in the air–water flow region. The range of unit discharge of water was varied from 0.06 to 0.20 m2/s. Three step configurations were studied: (i) without macro-roughness elements, (ii) with macro-roughness elements on each step, and (iii) with macro-roughness elements on each second step (AMR configuration). The results were compared in terms of onset flow conditions and internal air–water flow parameters such as local air concentration, mean air bubble chord length distribution, and air bubble frequency in the skimming flow regime. It was observed that the AMR configuration produced the maximum free-surface aeration among the other configurations. This alternative step geometry has potential for less cavitation damage than conventional step geometry because of the greater air entrainment.Key words: stepped chute, air-entrainment, air-water flow properties, macro-roughness elements, skimming flow.

scholarly journals Sediment Transport and Water Flow Resistance in Alluvial River Channels: Modified Model of Transport of Non-Uniform Grain-Size Sediments

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2038
Author(s):  
Gennady Gladkov ◽  
Michał Habel ◽  
Zygmunt Babiński ◽  
Pakhom Belyakov
Keyword(s):  
Sediment Transport ◽  
Water Flow ◽  
Transport Model ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Field Investigation ◽  
Empirical Modeling ◽  
River Channels ◽  
Channel Deformations ◽  
East European

The paper presents recommendations for using the results obtained in sediment transport simulation and modeling of channel deformations in rivers. This work relates to the issues of empirical modeling of the water flow characteristics in natural riverbeds with a movable bottom (alluvial channels) which are extremely complex. The study shows that in the simulation of sediment transport and calculation of channel deformations in the rivers, it is expedient to use the calculation dependences of Chézy’s coefficient for assessing the roughness of the bottom sediment mixture, or the dependences of the form based on the field investigation data. Three models are most commonly used and based on the original formulas of Meyer-Peter and Müller (1948), Einstein (1950) and van Rijn (1984). This work deals with assessing the hydraulic resistance of the channel and improving the river sediment transport model in a simulation of riverbed transformation on the basis of previous research to verify it based on 296 field measurements on the Central-East European lowland rivers. The performed test calculations show that the modified van Rijn formula gives the best results from all the considered variants.

scholarly journals Flow Characteristics and Grain Size Distribution of Granular Gangue Mineral by Compaction Treatment

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Ran Yuan ◽  
Dan Ma ◽  
Hongwei Zhang
Keyword(s):  
Weight Loss ◽  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Water Flow ◽  
Fine Particles ◽  
Flow Characteristics ◽  
Test System ◽  
Chemical Components ◽  
Gangue Mineral

A test system for water flow in granular gangue mineral was designed to study the flow characteristics by compaction treatment. With the increase of the compaction displacement, the porosity decreases and void in granular gangue becomes less. The main reason causing initial porosity decrease is that the void of larger size is filled with small particles. Permeability tends to decrease and non-Darcy flow factor increases under the compaction treatment. The change trend of flow characteristics shows twists and turns, which indicate that flow characteristics of granular gangue mineral are related to compaction level, grain size distribution, crushing, and fracture structure. During compaction, larger particles are crushed, which in turn causes the weight of smaller particles to increase, and water flow induces fine particles to migrate (weight loss); meanwhile, a sample with more weight of size (0–2.5 mm) has a higher amount of weight loss. Water seepage will cause the decrease of some chemical components, where SiO2 decreased the highest in these components; the components decreased are more likely locked at fragments rather than the defect of the minerals. The variation of the chemical components has an opposite trend when compared with permeability.

scholarly journals Modeling of Kinetics of Air Entrainment in Water Produced by Vertically Falling Water Flow

2014 ◽  
Vol 20 (3) ◽  
Author(s):  
Adelė VAIDELIENĖ ◽  
Arvaidas GALDIKAS ◽  
Paulius TERVYDIS
Keyword(s):  
Water Flow ◽  
Air Entrainment ◽  
Kinetics Of

Analysis of Runback Water Flow on Anti-Icing Surface Using Volume-of-Fluid Method

2017 ◽  
Author(s):  
Mei Zheng ◽  
Wei Dong ◽  
Zhiqiang Guo ◽  
Guilin Lei
Keyword(s):  
Heat Transfer ◽  
Water Flow ◽  
Thin Liquid Film ◽  
Flow Characteristics ◽  
Volume Of Fluid ◽  
Complex Model ◽  
Two Phase ◽  
Flow And Heat Transfer ◽  
Liquid Film Flow ◽  
The Mathematical Model

The runback water flow and heat transfer on the surface of aircraft components has an important influence on the design of anti-icing system. The aim of this paper is to investigate the water flow characteristics on anti-icing surface using numerical method. The runback water flow on the anti-icing surface, which is caused by the impinging supercooled droplets from the clouds, is driven by the aerodynamic shear forces and the pressure gradient around the components. This is a complex model of flow and heat transfer that considers flow field, super-cooled droplets impingement and runback water flow simultaneously. In this case of gas-liquid two phase flow, the Volume-of-Fluid (VOF) method is very suitable for the solution of thin liquid film flow so that it is applied to simulate the runback water flow on anti-icing surfaces in this paper. Meanwhile, the heat and mass transfer of the runback water flow are considered in the calculation using the User-Defined Functions (UDFs) in ANASYS FLUENT. The verification is conducted by the comparison with the results of the experimental measurement and the mathematical model calculation. The effect of the airflow velocity and contact angle on the water flow are also considered in the numerical simulation.

scholarly journals ANALYTICAL VERIFICATION OF OUTLET DEVICES CAPACITY OF LUBACHÓW STORAGE RESERVOIR ON THE BYSTRZYCA RIVER

2013 ◽  
Vol 35 (2) ◽  
pp. 49-66
Author(s):  
Jerzy Machajski ◽  
Dorota Olearczyk
Keyword(s):  
Water Flow ◽  
High Potential ◽  
Potential Threat ◽  
Storage Reservoir ◽  
Hydraulic Regime ◽  
Bottom Outlets ◽  
Analytical Verification ◽  
Discharge Curves

Abstract The Lubachów storage reservoir was built in the 1920’s. It is equipped with a relatively complex outlet installation, operating in variable hydraulic regime. The discharge deviations curves elaborated by German engineers for individual devices, after verification turned out to be burdened with a comparatively big error. This concerns especially the front spillway as well as intermediate outlets, and to a smaller degree the bottom outlets. The authors made a detailed analytical verification of the outlet installations and found great deviations from the currently valid discharge curves for these devices. Based on the analysis of conditions of computational discharges passage through the reservoir, they proved a high potential threat of water flow over the dam crest.

scholarly journals Hybrid Artificial Intelligence Methods for Predicting Air Demand in Dam Bottom Outlet

2021 ◽  
Author(s):  
Aliakbar Narimani ◽  
Moghimi ◽  
Amir Mosavi
Keyword(s):  
Artificial Intelligence ◽  
Economic Value ◽  
Air Entrainment ◽  
Operating Conditions ◽  
Successful Operation ◽  
Volume Rate ◽  
Hydraulic Equipment ◽  
Bottom Outlets ◽  
Hybrid Artificial Intelligence ◽  
Bottom Outlet

In large infrastructures such as dams, which have a relatively high economic value, ensuring the proper operation of the associated hydraulic facilities in different operating conditions is of utmost importance. To ensure the correct and successful operation of the dam's hydraulic equipment and prevent possible damages, including gates and downstream tunnel, to build laboratory models and perform some tests are essential (the advancement of the smart sensors based on artificial intelligence is essential). One of the causes of damage to dam bottom outlets is cavitation in downstream and between the gates, which can impact on dam facilities, and air aeration can be a solution to improve it. In the present study, six dams in different provinces in Iran has been chosen to evaluate the air entrainment in the downstream tunnel experimentally. Three artificial neural networks (ANN) based machine learning (ML) algorithms are used to model and predict the air aeration in the bottom outlet. The proposed models are trained with genetic algorithms (GA), particle swarm optimization (PSO), i.e., ANN-GA, ANN-PSO, and ANFIS-PSO. Two hydrodynamic variables, namely volume rate and opening percentage of the gate, are used as inputs into all bottom outlet models. The results showed that the most optimal model is ANFIS-PSO to predict the dependent value compared with ANN-GA and ANN-PSO. The importance of the volume rate and opening percentage of the dams' gate parameters is more effective for suitable air aeration.

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