scholarly journals Numerical modeling of spillway aerators in high-head dams

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
M. Cihan Aydin ◽  
Ercan Isik ◽  
A. Emre Ulu
Keyword(s):  
Numerical Analysis ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Air Entrainment ◽  
Experimental Results ◽  
Entrainment Rate ◽  
Viscous Effects ◽  
Cavitation Damage ◽  
Air Entrainment Rate ◽  
High Head

AbstractDue to high flow velocity, the spillway surfaces of high-head dams can expose to cavitational damage. The most effective and economical method of protection from this damage is aerated to flow using aerators. In this study, a spillway aerator of the roller-compacted concrete dam of 100 m height was analyzed using two-phase computational fluid dynamic model to overcome the cavitation damage on the spillway surface. The numerical analysis with prototype dimensions was performed for various flow conditions (5223, 3500, 1750 and 1000 m3/s of flow rate), and obtained results were compared with some experimental observation in the literature. Numerical and experimental results indicated that the cavitation occurs on the surface after a certain downstream point based on cavitation indices. The air entrainment rate and air concentrations supplied by means of the aerator were determined to avoid the cavitational damage. While the experimental results can contain considerable scale effect in terms of air entrainment rate owing to, e.g., viscous effects especially for small scales, the numerical models with prototype dimensions gave much more accurate results. In other words, it can be also mentioned that the actual aeration amount is much greater than that obtained from the model experiments. The results based on numerical analysis showed that the aerator device meet air demand to prevent the cavitation damage.

The Effect of Nozzle Type on Air Entrainment by Plunging Water Jets

2002 ◽  
Vol 37 (3) ◽  
pp. 599-612 ◽  
Author(s):  
Tamer Bagatur ◽  
Ahmet Baylar ◽  
Nusret Sekerdag
Keyword(s):  
Penetration Depth ◽  
Oxygen Transfer ◽  
Free Water ◽  
Air Entrainment ◽  
Water Jet ◽  
Transfer Efficiency ◽  
Entrainment Rate ◽  
Water Jets ◽  
Air Entrainment Rate ◽  
Oxygen Transfer Efficiency

Abstract In this study, for the plunging water jet aeration system using various inclined nozzle types, bubble penetration depth, air entrainment rate, water jet expansion, effect of water jet circumference at impact point, oxygen transfer coefficient and oxygen transfer efficiency which changed depending on the water jet velocity, were researched in an air-water system. Numerous studies were conducted with circular nozzles. The present study describes new experiments performed with different nozzle types. Three types of nozzles were examined, i.e., those with circular, ellipse and rectangle duct with rounded ends. Experimental results showed that water jets produced with ellipse and rectangle duct with rounded ends nozzles have very different flow characteristics, entrainment patterns on free water jet surface, and submerged water jet region within the receiving tank. Higher air entrainment rate and oxygen transfer efficiency was observed in the rectangle duct with rounded ends nozzle due to water jet expansion. Bubble penetration depth, however, is lower for the rectangle duct with rounded ends nozzle than for the other nozzles. The ellipse nozzle provided the highest bubble penetration depth. These results showed that it is appropriate to use ellipse nozzle in aeration of deep pool and rectangle duct with rounded ends nozzle in the applications where high bubble concentration is desirable.

Effect of Entrained Air on Cavitation Damage

1974 ◽  
Vol 1 (1) ◽  
pp. 97-107 ◽  
Author(s):  
S. O. Russell ◽  
G. J. Sheehan
Keyword(s):  
High Velocity ◽  
Additional Data ◽  
Air Entrainment ◽  
Test Facility ◽  
Hydraulic Structures ◽  
Cavitation Damage ◽  
Water Flows ◽  
Velocity Flow ◽  
High Head ◽  
Entrained Air

When water flows at high velocity over a surface, quite small boundary irregularities may trigger cavitation which can, in turn, cause extensive damage. Concrete surfaces downstream from high head outlet gates are particularly vulnerable to cavitation damage.Operating experience and previous experimental work suggest that cavitation damage can be greatly reduced and, in some cases, eliminated by entrained air in the water.Experiments were carried out with a special high head test facility in Vancouver to obtain additional data on the effect of air entrainment. These tests confirmed its effectiveness. In this paper, previous evidence is reviewed, the experiments are described, and the results presented. Finally suggestions are made about the design of hydraulic structures which involve high velocity flow.

Numerical Study of XCP Probe's Fluid Dynamic Characteristics

2011 ◽  
Vol 130-134 ◽  
pp. 1645-1649
Author(s):  
Ning Liu ◽  
Rui Zhang ◽  
Wen Yi Chen ◽  
Man Man Zhang
Keyword(s):  
Numerical Analysis ◽  
Drag Coefficient ◽  
Dynamic Characteristics ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Steady Motion ◽  
Experimental Results ◽  
Analysis Method ◽  
Test Parameters ◽  
Volume Method

Applied the finite volume method combining two-equations turbulence model,the influence of fluid dynamic characteristics on XCP probe under different factors be studied The fluid dynamic characteristics were researched under different influencing factors, such as falling speed, rotating rate,seawater density,etc. The drag coefficient under the different falling speeds and the limited velocity of submarine steady motion were obtained. Compared with the experimental results, the simulated results agree well with experimental results, the experiments have show the validity and feasibility of the numerical analysis method. These results will provide theory reference for selecting the reasonable rotating rate, analyzing stability and the movement rule of probe in the water, choosing suitable test parameters for XCP probe of different seawaters.

Numerical Analysis of Deformation and Failure of Penetration into Concrete Target by Projectile

2013 ◽  
Vol 804 ◽  
pp. 292-297 ◽  
Author(s):  
Song Gao ◽  
Ya Bin Wang ◽  
Xiu Feng Li
Keyword(s):  
Numerical Simulation ◽  
Numerical Analysis ◽  
Shear Failure ◽  
Failure Strain ◽  
Numerical Models ◽  
Experimental Results ◽  
Deformation And Failure ◽  
Material Parameters ◽  
The Military ◽  
Protection Engineering

Penetration is an important topic in the military and protection engineering field. Based on *MAT_PLASTIC_KINEMATIC of LS-DYNA program, this report studies effects of failure strain of the material parameters on structure of penetrating projectile. By establishing a group of numerical models about 45 steel hemispherical projectile penetrating semi-infinite concrete targets, this research aimed at analyzing effects of different failure strain values related to the destruction of the internal bracket structures of this projectile. At the same time, it studied the criterion of failure on finite dynamic program. The numerical results show that the use of failure strain in this model can well simulate damage of internal bracket structures of the projectile. Test was carried on based on this conclusion, which showed that bracket plate is subjected to shear failure in process of penetration, and numerical simulation was consistent with the experimental results.

Experimental and Numerical Analysis of a Pristine and a Nano-Modified Thermoplastic Adhesive

2018 ◽  
Author(s):  
Carlo Boursier Niutta ◽  
Raffaele Ciardiello ◽  
Giovanni Belingardi ◽  
Alessandro Scattina
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Numerical Analysis ◽  
Mechanical Behavior ◽  
Numerical Models ◽  
Surface Preparation ◽  
Experimental Results ◽  
Element Analysis ◽  
Piping Systems ◽  
Set Up

In this work, the mechanical properties of two different adhesives compositions have been investigated both experimentally and numerically. The studied thermoplastic adhesives are Hot-Melt Adhesive (HMA). In particular, a pristine and a nanomodified adhesive with 10% in weight of iron oxide have been considered. The adhesives have been subjected to a series of single lap joint (SLJ) tests using adherends made of polypropylene copolymer. As it is well-known, the structural-mechanical behavior of adhesive joints is mostly influenced by the bonding process: thickness of adhesive as well as its application procedures and the surface preparation of adherends are among the most influencing factors. In addition, the mechanical behavior of SLJ test is particularly influenced by the correct alignment of adherends and applied load. These aspects have been investigated, analyzing the experimental results. Moreover, the experimental results have been used to develop a numerical model of the two adhesives. The numerical analysis has been carried out using the commercial software LS-DYNA. Transient nonlinear finite element analysis has been performed to simulate the mechanical behavior of the thermoplastic adhesives. In particular, the cohesive formulations of the elements have been taken into consideration after a careful literature review. In order to set-up and to validate the mechanical properties of the adhesives, the experimental SLJ tests have been simulated. The developed finite element models enable to investigate more complex joint structures where these types of adhesives are used, such as plastic piping systems and automotive applications. Further, the numerical models allow to investigate with higher accuracy and lower time different aspects such as manufacturing and non-linear effects.

Estimation of the air entrainment characteristics of a transient high-pressure diesel spray

2005 ◽  
Vol 219 (8) ◽  
pp. 1025-1036 ◽  
Author(s):  
W Choi ◽  
B-C Choi
Keyword(s):  
High Pressure ◽  
Particle Image Velocimetry ◽  
Particle Image ◽  
Air Entrainment ◽  
Diesel Spray ◽  
Entrainment Rate ◽  
Recirculating Flow ◽  
Air Entrainment Rate ◽  
Image Velocimetry ◽  
Ambient Gas

The air entrainment characteristics of a transient high-pressure diesel spray were investigated with respect to time and location for injection pressures ( Pinj = 76 or 137 MPa) and ambient density (ρa = 15.6 kg/m3) under the non-evaporating condition (303 K). A particle image velocimetry analysis was introduced and some parameters were defined to express air entrainment characteristics. The air entrainment rate increased greatly as the flow moved downstream owing to a larger contact surface area and a recirculating flow. Higher pressure led to a greater entrainment rate with higher effectiveness. The speed (spray tip and front ambient gas) and volume (spray and laterally entrained gas) relations suggested the possibility for the renewal against the lateral-dominant entrainment mechanism.

Air entrainment rate and holdup in the Jameson cell

2007 ◽  
Vol 20 (8) ◽  
pp. 761-765 ◽  
Author(s):  
T. Taşdemir ◽  
B. Öteyaka ◽  
A. Taşdemir
Keyword(s):  
Air Entrainment ◽  
Entrainment Rate ◽  
Air Entrainment Rate

Experimental Study of the Influence of Different Weir Types on the Rate of Air Entrainment

2003 ◽  
Vol 38 (4) ◽  
pp. 769-783 ◽  
Author(s):  
M. Emin Emiroglu ◽  
Ahmet Baylar
Keyword(s):  
Experimental Study ◽  
Air Entrainment ◽  
Entrainment Rate ◽  
Empirical Correlations ◽  
Air Entrainment Rate ◽  
Maximum Penetration Depth ◽  
Longitudinal Slope ◽  
Maximum Penetration ◽  
Labyrinth Weirs ◽  
Better Than

Abstract Aeration is used in water treatment to alter the concentration of dissolved gases, to strip volatile organics, and to reduce tastes and odours. This can be obtained by creating turbulence in the water. One method of producing such turbulence is via the overflow jets downstream of weir structures. This paper investigates the effect of varying weir types on the air entrainment rate. Empirical correlations predicting the maximum penetration depth and air entrainment rate were developed for different weir types. It is demonstrated that the air entrainment rate of the broad-crested weirs is generally much better than for the sharp-crested weir and the labyrinth weirs. The air entrainment rate increased as the weir longitudinal slope of the broad-crested weirs and the weir sill slope of the labyrinth weirs became larger.

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