scholarly journals Impact of Bed Material on the Local Scour Downstream Fayoum Type Weir with Various Designs of Floor Jets

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Ahmed Mahmoud Ibraheem
Keyword(s):  
Local Scour ◽  
Medium Sand ◽  
Stilling Basin ◽  
Water Jets ◽  
Materials By Design ◽  
Stilling Basins ◽  
Bed Materials ◽  
Tail Water ◽  
Bed Material ◽  
Fine Gravel

Local scour downstream hydraulic structures should be studied well to avoid damage or even failure of these structures. In this paper, an experimental model was conducted to study the influence of bed material size on the local scour downstream stilling basins of Fayoum type weir as a hydraulic structure. Two bed material were tested. The model included stilling basin and five rows of water jets. Forty-five test runs were carried out for each bed material. Different cases were implemented during this study including three flow discharges, three tail water depths and five various designs of floor jets. Based on the obtained results, it was found that the maximum and minimum scour depths for the two bed materials occurred by design A and design D. The maximum scour lengths happened for medium sand by design C and for fine gravel by both designs A and E, while the minimum scour lengths were recorded for medium sand by design D and for fine gravel by design A. The maximum scour volumes were found for the two bed materials by design A, while the minimum scour volumes occurred by both designs C and D for medium sand and by design E for fine gravel. Employing fine gravel instead of medium sand as a bed material achieved maximum reduction percentages of 86.8 %, 53.3 % and 89.8 % for scour depth, scour length and scour volume, respectively.

scholarly journals Effect of Angled Submerged Vanes on Bed Morphology Downstream Sluice Gate

2019 ◽  
pp. 1-16
Author(s):  
M. M. Ibrahim
Keyword(s):  
Local Geometry ◽  
Sluice Gate ◽  
Stilling Basin ◽  
Stilling Basins ◽  
Current Water ◽  
Bed Materials ◽  
Submerged Vanes ◽  
Bed Material ◽  
The Impact ◽  
Flowing Stream

Scour is a characteristic marvel caused because of the erosive activity of flowing stream on alluvial beds which expels the silt around or close structures situated in streaming water. In this paper, an experimental study was directed to foresee the impact of oriented vanes introduced on level stilling basin downstream a sluice gate on bed material planning to limit the local geometry of scour and silting. The considered shape in this exploration is easy to be utilized as an additional component to be implemented on the stilling basin of any current water structures. Two hundred and sixty runs were executed using 10 models of stilling basins considering different heights and angles of vanes under various flow conditions including the discharges and tail gate water depths. An instance of level floor without vanes was incorporated into the test program to foresee the impact of vanes establishment. The experimental outcomes were accounted for 2 distinctive bed materials. Results were analyzed and graphically introduced. Simple formulas were given to estimate the geometry of the local scour and silting.

scholarly journals Influence of Using Floor Jets on the Local Scour Downstream Fayoum Type Weir

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Gamal Elsaeed ◽  
Abdelazim M. Ali ◽  
Alaa Nabil El-Hazek ◽  
Ahmed Mahmoud Ibraheem
Keyword(s):  
Optimum Design ◽  
Local Scour ◽  
Hydraulic Structures ◽  
Base Case ◽  
Optimal Arrangement ◽  
Stilling Basin ◽  
Water Jets ◽  
Complete Failure ◽  
Tail Water ◽  
Water Depths

Local scour downstream hydraulic structures may cause damage or complete failure of these structures. In this paper, an experimental study was carried out to investigate using floor water jets as a mitigation measure to minimize the local scour downstream stilling basin and to clarify the best arrangement of these jets. Different cases were established during this study including different flow discharges, tail water depths and floor jet locations. A base case without using water jets was included to estimate the influence of using suggested water jets arrangements. Additional four cases for various jets arrangements were established and studied. Obtained results were analyzed and graphically presented. The optimum design was easy to be used for increasing the performance of stilling basin. The results indicated that the optimal arrangement of floor jets was the case (D), where the last three rows of floor jets were used. This optimum design results in a reduction in maximum scour depth ranged from 44.53 % to 76.15 % and reduction in scour length ranged from 25.00 % to 71.93 % compared to the base case.

Erosion of unconsolidated gravel beds

1985 ◽  
Vol 12 (3) ◽  
pp. 559-566 ◽  
Author(s):  
S. P. Chee ◽  
E. M. Yuen
Keyword(s):  
Analytical Study ◽  
Local Scour ◽  
Hydraulic Control ◽  
Control Structures ◽  
Gravel Beds ◽  
Water Jets ◽  
River Bed ◽  
Motion Condition ◽  
Scour Hole ◽  
Tail Water

In any riverbed degradation phenomenon, the vertical dimension of the deepest part of the scour hole is a pertinent parameter since all the other erosion parameters describing the configuration of the scour hole depend on its numerical value. Hence, it is necessary to be able to evaluate the maximum depth of the scour hole.For most practical situations, the impingement of submerged water jets on a granular riverbed occurs at an angle, and it is the object of this study to include the effects of obliqueness in the analysis. Some examples of the effects of impingement by water jets are the erosion problems caused by plunging water jets from hydraulic control structures as they discharge into the tail-water downstream.Basic to an understanding of the mechanism of local scour is the concept of "initiation of motion." Hence, the analytical study will use this concept to derive generalized relations that will link the incipient motion condition at the deepest point of the scour hole with the numerical value of the scoured depth. In addition, care was taken to ensure that only those hydraulic variables that are frequently used in hydraulic engineering design are included in the analysis in order to make the results useful to practicing engineers. Key words: local scour, maximum erosion, river bed, plunge basin, diving jets, energy dissipation, riverbed degradation.

scholarly journals Application of neuro-fuzzy model to estimate the characteristics of local scour downstream of stilling basins

2009 ◽  
Vol 12 (2) ◽  
pp. 201-211 ◽  
Author(s):  
J. Farhoudi ◽  
S. M. Hosseini ◽  
M. Sedghi-Asl
Keyword(s):  
Fuzzy Model ◽  
Local Scour ◽  
Bridge Piers ◽  
Type I ◽  
Effective Parameters ◽  
Promising Alternative ◽  
Neuro Fuzzy ◽  
Scour Hole ◽  
Stilling Basins ◽  
Tail Water

The local scour phenomenon in the vicinity of bridge piers and stilling basins has received considerable attraction from designers due to its consequences which may endanger these structures. Various factors govern the pattern of scour evolution which results in the complexity of this phenomenon. Many researchers indicated that the use of fuzzy logic in modeling this phenomenon could be a promising alternative to reflect the vagueness and ambiguity of effective parameters. The aim of this study is to investigate the performance of a neuro-fuzzy model based on Takagi and Sugeno's theory in estimating the maximum depths, pattern and time evolution of scour hole downstream of a stilling basin of U.S.B.R. type I. The investigation was conducted under various discharges, tail-water depths (low, balanced and high), different bed materials and model sizes. The characteristics of the equilibrium state of the scour phenomenon as well as the time to reach the maximum scour depth were considered. The results showed a significant conformity between estimated and experimental data which recommends an acceptable outcome using a neuro-fuzzy model to forecast the properties of scour hole downstream of stilling basins. This would contribute to predicting the design geometry of stilling pools and taking the appropriate precautions to protect the downstream channel bed.

scholarly journals Experimental Investigation of Oxygen Carrier Aided Combustion (OCAC) with Methane and PSA Off-Gas

2020 ◽  
Vol 11 (1) ◽  
pp. 210
Author(s):  
Viktor Stenberg ◽  
Magnus Rydén ◽  
Tobias Mattisson ◽  
Anders Lyngfelt
Keyword(s):  
Oxygen Carrier ◽  
Silica Sand ◽  
Fuel Conversion ◽  
Fuel Gas ◽  
Bed Temperature ◽  
Bed Materials ◽  
Distribution Plate ◽  
Bed Material ◽  
Gas Conversion ◽  
No Emissions

Oxygen carrier aided combustion (OCAC) is utilized to promote the combustion of relatively stable fuels already in the dense bed of bubbling fluidized beds by adding a new mechanism of fuel conversion, i.e., direct gas–solid reaction between the metal oxide and the fuel. Methane and a fuel gas mixture (PSA off-gas) consisting of H2, CH4 and CO were used as fuel. Two oxygen carrier bed materials—ilmenite and synthetic particles of calcium manganate—were investigated and compared to silica sand, an in this context inert bed material. The results with methane show that the fuel conversion is significantly higher inside the bed when using oxygen carrier particles, where the calcium manganate material displayed the highest conversion. In total, 99.3–99.7% of the methane was converted at 900 °C with ilmenite and calcium manganate as a bed material at the measurement point 9 cm above the distribution plate, whereas the bed with sand resulted in a gas conversion of 86.7%. Operation with PSA off-gas as fuel showed an overall high gas conversion at moderate temperatures (600–750 °C) and only minor differences were observed for the different bed materials. NO emissions were generally low, apart from the cases where a significant part of the fuel conversion took place above the bed, essentially causing flame combustion. The NO concentration was low in the bed with both fuels and especially low with PSA off-gas as fuel. No more than 11 ppm was detected at any height in the reactor, with any of the bed materials, in the bed temperature range of 700–750 °C.

Relationship Between Feedstock Characteristics and Erosivity of FBC Bed Materials

1992 ◽  
Vol 114 (1) ◽  
pp. 145-151
Author(s):  
A. V. Levy ◽  
B. Q. Wang ◽  
G. Q. Geng
Keyword(s):  
Heat Exchangers ◽  
Major Effect ◽  
Plain Carbon Steel ◽  
Sand Content ◽  
Degradation Mechanisms ◽  
Sharp Transition ◽  
Fluid Bed ◽  
Alkali Compounds ◽  
Bed Materials ◽  
Bed Material

The erosion-corrosion (E-C) metal wastage mechanisms and rates that occur in 1018 plain carbon steel used in tubular heat exchangers of fluid bed combustors (FBC) are discussed. The characteristics of FBC bed material erodent particles such as composition, shape, size, and strength were found to have a major effect on the surface degradation mechanisms and rates that occurred. A total of 16 different bed material particles from ten different FBCs were tested. It was determined that when the particles were strong enough not to shatter when they impacted the steel’s surface, their shape and composition were the most important factors in determining their erosivity. The relative amounts of SiO2, CaO, CaCO3, CaSO4, and alkali compounds in the bed materials were related to the metal wastage by using laboratory mixtures of the compounds as erodents. The ratio of SiO2 to CaO and CaCO3 was especially important in determining the erosivity of the bed materials. It was found that increasing this ratio increased the metal wastage. A sharp transition ratio occurred on either side of which the metal wastages were linear. The slope of the linear curve was low for the lower sand content mixtures and higher for higher sand content mixtures. The transition ratio required a higher CaO content for higher velocity particles.

Local Scour Downstream of Positive-Step Stilling Basins

2009 ◽  
Vol 135 (10) ◽  
pp. 846-851 ◽  
Author(s):  
Giuseppe Oliveto ◽  
Victor Comuniello
Keyword(s):  
Local Scour ◽  
Stilling Basins ◽  
Positive Step

scholarly journals Energy Dissipation in Solid Roller Bucket and Controlled Stilling Basin for Ogee Stepped Spillway

2019 ◽  
Vol 8 (4) ◽  
pp. 2109-2112
Keyword(s):  
Energy Dissipation ◽  
Laboratory Experiments ◽  
Ideal Condition ◽  
Stepped Spillway ◽  
Type Ii ◽  
Dimensional Parameter ◽  
Stilling Basin ◽  
Sequent Depth ◽  
Tail Water ◽  
The Ideal

Hydraulic jump type II stilling basin is generally preferred as an energy dissipator for ogee spillway but it is uneconomical due to longer structure. On the other hand, roller bucket uses relatively shorter structure over a sloping apron or horizontal stilling basin. In this study, an attempt has been made to evaluate the performance of an ogee profile stepped spillway in combination with solid roller bucket and stilling basin type II for energy dissipation. Laboratory experiments are performed on a physical working model of ogee profile stepped spillway at discharge ranging from 0.0032 to 0.0069 m3 /s for a head of 1.5m, 4m & 7m and the results compared for energy dissipation (non-dimensional parameter (y c / h) = 0.69). The model results show that stepped spillway model without v-notch achieves 92.40 % energy dissipation. Thus this model is found to be more suitable to acquire the ideal condition of sequent depth and tail water depth in stilling basin for all the discharges.

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