Weir Structure Research Articles

Comparison of Fluid Flow and Tracer Dispersion in Four-Strand Tundish under Fewer Strand Casting and Sudden Blockage of Strand Conditions

The study focuses on the four-strand tundish as the research object, aiming at the phenomenon of fewer strand casting (stable blockage) and sudden blockage of the tundish in industrial production. Numerical simulation methods are employed to compare the velocity vectors, flow fields, residence time distribution (RTD) curves, and outflow percentage curves under stable blockage and sudden blockage of the tundishes with a double-weir structure, U-shaped weir structure, and U-shaped weir structure with holes in the front. The results indicate that, after sudden blockage of the tundish strands, the flow field transitions from an unstable four-strand flow field to a stable three-strand flow field. Both the double-weir tundish and the U-shaped weir tundish reach a stable state after 200 s, while the U-shaped weir tundish with holes in the front reaches stability after 150 s. Additionally, compared to other structures, the tundish strands of the U-shaped weir with holes in the front are less affected by blockage, showing better consistency among strands and better adaptability under non-standard casting conditions.

Protective Measures for Scouring Effects in Serayu Micro Hydro Integrated Barrage

Adding a new micro hydropower component to an established barrage, such as the Serayu Barrage in Central Java Province, poses significant structure risks and potentially compromises the stability of the structures. To mitigate these negative impacts, physical modeling was conducted at our hydraulic laboratory to accurately replicate 600 meters of the Serayu River, including the 110-meter-wide Serayu Barrage structure at a scale of 1:40. Multiple scenarios were examined to simulate hydrodynamic conditions and sediment transport along the barrage structure. Notably, downstream scouring conditions were identified as a crucial parameter affecting the structure’s stability. Results obtained using a design discharge of 2,470 m3/s revealed concerning findings, with an observed 4 to 6 meters deep scouring downstream near the end sill of the weir. Immediate mitigation measures using riprap are imperative to prevent further damage to the weir structure. This paper investigates several configurations for riprap protection to address the scouring problems. After implementing a full riprap arrangement downstream of the end sill, the scouring depth was reduced significantly and pushed far downstream. Looking at it from an economic standpoint, placing a full riprap configuration for downstream protection is a more financially efficient option over an extended period.

Flap Gate Weir Structural Design Using FEA

A flap gate weir commonly use to raise the level of a river or stream. It is a device that is used to regulate the flow of water in a river. It is typically located at the upstream of the river. Basically, flap gate weir is submerged under water, so hydrostatic force acting on submerged surfaces weir. The traditional design and analysis the resultant force acting on a submerged weir surface must specify magnitude of the force, direction of the force and line action of the force all is assumed on 2D which take long time calculation and might mistake. The aims of this paper is using finite element method design and study the flap gate weir structure instead of traditional analysis. In this paper the 3D model of flap gate weir was created by SolidWorks as assembly of flap gate weir which the flap gate weir was inclined 30 degrees and imported into Ansys Workbench for boundary conditions and calculations. The result from Ansys is used to find the specific hydraulic cylinder as the system needed. And modal analysis to check the vibration of the flap gate weir. By using finite element analysis the results study is satisfy by get results faster, know total deformation, know weak point and know where reinforce pad should put in and saving cost of materials when compare with traditional analysis.

A magnetic solid phase extraction microfluidic chip coupled with gas chromatography-mass spectrometry for the determination of polycyclic aromatic hydrocarbons in aqueous samples

In this paper, we designed and manufactured a reliable magnetic solid phase extraction (MSPE) microfluidic chip for determination of polycyclic aromatic hydrocarbons (PAHs) in water combined with gas chromatography-mass spectrometry. Sample loading, washing and elution are implemented with microinjection pump and integrated on a single chip, which reduced manual operation. Magnets were used to fix octadecyl/phenyl bifunctional Fe3O4@SiO2 extractant to avoid the design of weir structure in extraction chamber. The whole microfluidic chip was simple and low cost. Based on the microfluidic chip extraction platform, the on-chip MSPE method for the determination of PAHs was optimized and established. The results showed that this method required only 2 mL of sample, 2 mg of extractant, and 50 μL of elution organic solvent for whole on-chip MSPE process, which was environmentally friendly and consistent with green chemistry. Method verification results were displayed which the linear range of five PAHs was between 1-100 ng/mL with good linearity (R2≥ 0.9985), and the detection limits (S/N = 3) were 0.08–0.26 ng/mL. The RSDs of intra-day precision (n=6) and inter-day precision (n=9) for PAHs were less than 6.1 % and 7.2 %, respectively. Enrichment factors were determined to be 31.3–37.7. The recoveries of river water, tap water, bottle water, waste water and urine at three spiked levels were in the range of 89.9% to 113.7% and the matrix effect values were between 83.8% to 109.6%. The extraction platform has the advantages of accurate analysis, simple design and cost-effective, which is conducive to the widespread use of microfluidic chips

Optimised multi-objective design of weir structures

Diversion head works, also called weirs or barrages, are structures constructed across rivers or canals to store water or raise the water level. The design of diversion weir structures involves calculating the depth, length and thickness of the horizontal and sloping aprons and sheet pile cut-offs. The design parameters of a diversion weir structure, which have complex non-linear relationships, are traditionally determined using empirically derived recommendations and iterations to achieve structural stability against failures due to scour, uplift, sliding, piping and overturning. However, current design approaches do not explicitly explore the trade-offs between the many relevant design objectives and thus fail to reveal possibly superior designs. A multi-objective optimisation design approach for a diversion weir structure is proposed in this article. A free and open-source code that can be used as a design tool is also provided. The method is demonstrated on a stylised design problem. The results show that the method reveals solutions with diverse balances of stability metrics and cost, with the optimal relationships of parameter values of components also varying based on the relative cost of the construction materials for sheet piles and aprons.

An Experimental Study of a Combined Oblique Cylindrical Weir and Gate Structure

In the present study, the effects of different oblique angles and diameters on the cylindrical weir and below a gate as a combined device have been studied experimentally. For this purpose, sixteen models of combined cylindrical weir-gate structures have been tested in a laboratory flume. These models had four different oblique angles α (300, 450, 600, and 900). For each angle, the diameter of cylindrical weir-gate changed four times (4, 7.3, 9, and 11cm). The results of all models indicate that the theoretical discharge (Qth) is inversely proportional to the ratio of diameter to height (D/h) and length to height (L/h). As the diameter increases and oblique angles decrease, the actual discharge (Qact) increases. A general expression was established linking Qth/g1/2h5/2 and the discharge coefficient Cd with D/h, L/h, and alfa. The discharge coefficient ranged from 0.55 to 0.99 for various oblique angles and decreased as the angle increased. A strong correlation was observed between the estimated and the calculated values.

Discharge Coefficient of Symmetrical Stepped and Triangular Labyrinth Side Weirs in a Subcritical Flow Regime

The labyrinth side weir structure is an optimal solution to regulate and divert excess flows across rivers, and irrigation and drainage channels when the opening length of the side weir is limited. Changing the geometry of the side weir is considered one way to improve its efficiency. The present study investigates the hydraulic effects of stepped labyrinth side weirs to increase their discharge capacity. To estimate the outflow over symmetrical stepped labyrinth side weir, the discharge coefficient needs to be determined. Normal triangular labyrinth side weir in one cycle mode has been modified by increasing the crest path using different steps. A total of 417 experiments were conducted on normal and stepped side weirs for various weir opening lengths, weir heights, internal head angles, and hydraulic conditions. The results were analyzed and compared. It was found that efficiency improved, and the discharge coefficient increased as the number of the steps decreased. Furthermore, the water surface profile becomes more uniform with decreasing number of steps. A lower number of steps, smaller head angle, and high weir length produce a higher discharge coefficient by approximately 15%–35% compared to a normal triangular labyrinth side weir; in addition, the Knope length decreases by approximately 40%–70% for the same effective length. Additionally, a reliable equation to estimate the discharge coefficient of the stepped labyrinth side weir was presented. The results of this study can be used to design side weirs with high hydraulic performance when the weir-included angle selected is small or there is a lack of space.

Investigating a new approach to enhance the discharge capacity of labyrinth weirs

AbstractClimate change has caused the inefficient operation of a significant number of old weirs to pass large discharges. Therefore, this study aims to increase the discharge capacity of the labyrinth weir. A new approach was proposed by modifying a labyrinth weir structure. The data was obtained from the quarter-round crest and different sidewall angles ranging from 8 to 35°. A conventional labyrinth weir was used for comparison. The results showed that the percentage of the notches area to sidewalls area of the weir (An/Aw) does not exceed 8%. Also, the percentage of the notches' length to total crest length (ΔL/Lc) does not exceed 32%. Also, the percentage of the notch depth to the sidewall depth (ΔP/P) does not exceed 30%. The other parameters are kept constant. These dimensionless terms provided a maximum compound coefficient of discharge of 0.74. Also, the compound discharge coefficient initially increased at low water head ratios and decreased at higher values of water head ratios. The regression empirical equations were generated. The maximum increase in efficiency was 10% for a sidewall angle of 6° when compared to conventional labyrinth weirs. The maximum improvement of the compound coefficient of discharge was 18.8% for a sidewall angle of 8°.

An archaeological example of Aboriginal management of a hydro-ecological system in the Murray River valley, South Australia

Context A rare archaeological example of Aboriginal water management in a Murray River floodplain upstream of Renmark is described and contextualised. Aims Historical accounts, archaeological descriptions and hydrological modelling are used to propose a likely function of the site. Methods The site was documented through archaeological field recording, a digital elevation model (DEM) developed through a real-time kinematic (RTK) survey and flood inundation modelling (FIM), and is interpreted through a review of archival and documentary sources. Key results The site represents one of only a few extant physical examples of Aboriginal water management in the Riverland and greater Murray–Darling Basin. Conclusions Our assessment indicates that Aboriginal people had excavated an artifical channel within the Calperum floodplain in order to manipulate natural water connectivity, most likely as part of a fish trap or weir structure. Implications The site builds an appreciation of the complexity of Aboriginal land practices and supports the impression gained though historical accounts of a curated and managed riverscape.

The Influence Research on Nitrogen Transport and Reaction in the Hyporheic Zone with an In-Stream Structure.

The hyporheic zone (HZ) is important for river ecological restoration as the main zone with nitrogen biochemical processes. The engineering of river ecological restoration can significantly change the hydrodynamics, as well as solute transport and reaction processes, but it is still not fully understood. In this study, nitrogen transport and reaction processes were analyzed in the HZ with an in-stream weir structure. An HZ model was built, and three reactions were considered with different design parameters of the weir structure and different permeability characteristics of porous media. The results show that a structure with a greater height on the overlying surface water enables the species to break through deeper porous media. It promotes the mean spatial reaction rates of nitrification and denitrification and results in increased net denitrification in most cases. In addition, increasing the burial depth of the structure leads to the same variation trends in the mean spatial reaction rates as increasing the structure height. Larger permeability coefficients in porous media can enhance flow exchange and increase mean spatial reaction rates. The results can help deepen the understanding of nitrogen transport and transformation in the HZ and optimize the design parameters and location of the in-stream structure.

MODIFIKASI KOLAM OLAK TIPE AMBANG BERGIGI DALAM RANGKA REHABILITASI KERUSAKAN BENDUNG CIKEUSIK DI JAWA BARAT

The presence of hydraulic jumps downstream of the weir structure is a natural occurrence that indicates a change in supercritical to subcritical flow characteristics. Hydraulic jump is one indicator of the dissipation of energy in the stilling basin. Therefore, the absence of a hydraulic jump can be a problem for some weirs, as happened in the Cikeusik Weir, which experienced damage to the stilling pool floor so that the energy dissipation did not function optimally. This paper will discuss the potential causes of damage to the Cikeusik weir and alternative designs for its countermeasures. A physical model test was carried out in the laboratory with a scale of 1: 40 to obtain an appropriate alternative to the stilling pond design for the Cikeusik weir. The tests were carried out with variations in the discharge Q2 years, Q25 years, and Q100 years, respectively. Three model tests were conducted, namely the existing and two modified designs. Based on the model testing results, extending stilling basin floor length with a dentated end sill and adding downstream riprap is the most optimal alternative because it has an energy reduction effectiveness of up to 80% and the lowest downstream scour potential compared to other options. The results of this test are expected not only to be used as an alternative to mitigate the damage to the Cikeusik weir but also to other locations that have similar problems. Keywords : Cikeusik Weir, stilling basin, Froude number, local scour, physical model

A unified formula for discharge capacity of street inlets for urban flood management

Street inlets play a key role in intercepting surface runoff into underground drainage systems, which can reduce the hazard degree during urban flood events. An accurate calculation of the discharge capacity of street inlets is vitally important in numerically modelling urban floods and managing flood resilience. A series of laboratory experiments were combined with a theoretical analysis in this study to investigate the conveyance characteristics of a typical street grate inlet. A large-scale laboratory platform was constructed, consisting of an upper-layer model street and an underground measuring system installed with a V-notch weir structure. A model street inlet was used to connect the upper and underground layers, which had a complete drainage structure including: an inlet grate, a drain box, and a connection tube. A total of 78 experimental runs were conducted using this laboratory platform, and the discharges intercepted by the grate inlet were measured for a range of incoming water depths and flow velocities, where the approaching Froude number varied from 0.05 to 0.89. These experimental results showed that the drainage pattern of the street inlet was converted from weir flow to orifice flow after the drain box was fully pressurized. In addition, a power function was derived between the relative drainage velocity through the inlet and the approaching Froude number, based on the method of dimensional analysis, and a unified formula was proposed to calculate the discharge capacity of street inlets. The corresponding coefficients in the formula were calibrated using the laboratory measurements. The unified discharge capacity formula was verified using other experimental results obtained from previous studies, and the results indicated that the calculated results using the unified formula agreed well with these measurements, with the coefficients of R2 > 0.90. Therefore, the unified formula for discharge capacity of street inlets obtained from the study reported herein has a high predictive accuracy, which can be used in numerical modelling and risk management of urban floods.

THE EFFECTIVENESS NUMBER OF BAFFLE BLOCKS TO REDUCE ENERGY IN TUKUTAHA TRANSITION CHANNELS

One of the causes of damage to the weir structure is scouring. Scouring may occur along the weir channel. Scouring occurs due to the high flow velocity and high specific energy. One of the methods used to reduce specific velocity and energy is by installing baffle blocks in parts that have high-velocity and energy. The addition of baffle blocks is carried out at a place that has a high-velocity, namely the transition channel. To see the effect of baffle block variation on velocity and energy, a study was conducted. The study was conducted with four baffle block type models. The type 0 model is a baffle block installation pattern based on the initial design. Type 1 model is designed based on the planning of The Colorado State University (CSU) rigid boundary basin. Type 2 model is designed by reducing the number of baffle blocks from the initial design of 102 baffles to as many as 75 baffles. while the 3 channel type model transitions without baffle blocks. Based on the analysis of % energy loss in the transition channel, the type 0 model produces the largest energy loss. The type 0 model at maximum discharge has a % energy loss 10.821% greater than the type 1 model, 14.889% greater than the type 2 model and 33.02 % greater than the type 3 model.

Prediction of discharge coefficients for broad-crested weirs using expert systems

ABSTRACT Broad crested weirs can be used to make discharge measurements in irrigation canals; the entrance of stepped weirs or chutes are sometimes designed as a broad crested weir structure. These structures are also sometimes used for the dam body. In this study, the Artificial Neural Network (ANN) and M5 model tree methods are used to predict discharge coefficients (Cd ) for broad crested weirs. The results from these two models are compared with nonlinear regression equations. Four series of data obtained from different rectangular broad crested weirs have been used and important dimensionless parameters have been defined. Results show that the ANN procedure is superior to the M5 model and regression approaches. The accuracy for ANN is quantified by R = 0.966 and RMSE = 0.038. All the three methods are able to provide a reasonable prediction for Cd ; the M5 model tree provides four linear equations that can be used to estimate Cd . The shape of the Cd contours shows that the effect of weir height (P) exceeds that of the weir length (L).

Seismic probabilistic risk assessment of weir structures considering the earthquake hazard in the Korean Peninsula

Seismic safety evaluation of weir structure is significant considering the catastrophic economical consequence of operational disruption. In recent years, the seismic probabilistic risk assessment (SPRA) has been issued as a key area of research for the hydraulic system to mitigate and manage the risk. The aim of this paper is to assess the seismic probabilistic risk of weir structures employing the seismic hazard and the structural fragility in Korea. At the first stage, probabilistic seismic hazard analysis (PSHA) approach is performed to extract the hazard curve at the weir site using the seismic and geological data. Thereafter, the seismic fragility that defines the probability of structural collapse is evaluated by using the incremental dynamic analysis (IDA) method in accordance with the four different design limit states as failure identification criteria. Consequently, by combining the seismic hazard and fragility results, the seismic risk curves are developed that contain helpful information for risk management of hydraulic structures. The tensile stress of the mass concrete is found to be more vulnerable than other design criteria. The hazard deaggregation illustrates that moderate size and far source earthquakes are the most likely scenario for the site. In addition, the annual loss curves for two different hazard source models corresponding to design limit states are extracted.

Two-Dimensional Numerical Modeling of Flow in Physical Models of Rock Vane and Bendway Weir Configurations

While there are a wide range of design recommendations for using rock vanes and bendway weirs as streambank protection measures, no comprehensive, standard approach is currently available for design engineers to evaluate their hydraulic performance before construction. This study investigates using 2D numerical modeling as an option for predicting the hydraulic performance of rock vane and bendway weir structure designs for streambank protection. We used the Sedimentation and River Hydraulics (SRH)-2D depth-averaged numerical model to simulate flows around rock vane and bendway weir installations that were previously examined as part of a physical model study and that had water surface elevation and velocity observations. Overall, SRH-2D predicted the same general flow patterns as the physical model, but over- and underpredicted the flow velocity in some areas. These over- and underpredictions could be primarily attributed to the assumption of negligible vertical velocities. Nonetheless, the point differences between the predicted and observed velocities generally ranged from 15 to 25%, with some exceptions. The results showed that 2D numerical models could provide adequate insight into the hydraulic performance of rock vanes and bendway weirs. Accordingly, design guidance and implications of the study results are presented for design engineers.

Experimental analysis of flow characteristics over hydrofoil weirs

The rounded crested weirs are commonly used for discharge measurements and this overflow structures have advantages such as stable overflow pattern and good accuracy. Hydrofoil weirs with streamlined properties are similar to the ogee weirs and can be used as a spillway profile. The hydraulic features of flow over hydrofoil weirs created by the NACA0018, NACA0021 and NACA0024 hydrofoil geometry placed in an open channel are investigated experimentally under free-flow conditions. The velocity field of hydrofoil weir flows are measured by one-dimensional Laser Doppler Anemometer. Experimental velocity profiles are measured along the middle section of the channel, especially around the weir structure, to determine the boundary layer separation. According to the determination of optimum weir structure the free surface profiles, pressure distributions on weir surfaces, experimental discharge coefficients and head losses over weir structures are determined for different structure and flow conditions. Pressure distributions over the hydrofoil weir are presented. In addition, the relationships between discharge coefficient (Cd) and flow rate (Q), specific total head (H/R), relative weir height (P/H), relative total head (H/P) and dimensionless total energy head upstream of the weir (H/L) are investigated.

Historical Structures and Technical Heritage on the Elbe-Vltava Waterway

The paper describes the past development of the Elbe-Vltava waterway (EVW) and focuses on the documentation and presentation of the historical structures which were built for the rivers’ continuous navigability. Modern modifications of the waterway started at the beginning of the 19th century and focused mainly on regulatory work aimed at widening, straightening and deepening the fairway and removing the narrow fairway sections. In 1896, the Commission for Channelling the Vltava and the Elbe Rivers in Bohemia was established. The commission began implementing a plan to canalise the Elbe-Vltava waterway. On the EVW, a cascade of 34 barrages have been built, which are connected by their backwaters and ensure year-round navigability of the Vltava River from the Slapy Dam to the town of Mělník (92 km) and the Elbe River from the town of Chvaletice to the city of Ústí nad Labem (172 km). The last section of the Elbe River between Ústí nad Labem and the border with the Federal Republic of Germany (41 km) has so far been made navigable only by historical regulation works. Barrages on the EVW are typically composed of a weir structure, a navigation lock, a hydroelectric power plant producing renewable energy and a fish pass or sport whitewater canal. Most of these structures were built in the first half of the 20th century and represent a huge and unique technical heritage that still serves its purpose. The development of the EVW objects was documented in detail. The result is a software designed as a computer application with a web interface, which also serves for the presentation of technical heritage using original and modern technologies. Database operations enable the sharing of more information resources by competent organizations in the area of management, operation and maintenance of objects on the EVW. The system contains detailed descriptions of individual objects including their main technical parameters. For all the barrages were also systematically documented archival historical documents, maps, drawing documentation, photo gallery and for the most important barrages a description of the architectural design. The research also focused on mapping the development of regulatory adjustments of the Elbe River based on preserved historical documentation from the 19th and 20th centuries and the first aerial photographs since 1938. The presentation for the general public is complemented by an index of prominent personalities who contributed to the development of the EVW. There is also an explanatory dictionary of technical elements and objects on the EVW, including functional diagrams. Tourist attractions around the waterway are also included in the software.

Hydraulic Modelling of Riverbed Embankment Under the Hričov Weir

The weir of the Hričov water structure has an untypical shortened stilling basin, which affects significant scour development in the downstream riverbed. A rockfill embankment structure adjacent to the stilling basin was constructed to prevent the formation of scours in the riverbed. However, increased flows at the weir erode this fortification and it is necessary to replenish the material back to the embankment after the flow situations. A 2D hydraulic model constructed in a flume of the Hydraulic laboratory was used for the research of new downstream fortification, which would be better resist the scouring effects. The model was created according to Froude’s modelling similarity as a 2D model of the weir structure with control gates and part the downstream riverbed consisting of gravel. Different designs of the embankment were not allowed to interfere with the existing construction of the water structure. The construction of the embankment was designed as a concrete “secondary” stilling basin adjacent to the existing one. Tested variants of the embankment were of different length and depth of the stilling basin. The length varied from 11 to 24 m and the depths varied from 0 to 1,8 m. Overall 11 different design of the embankment were investigated. Each design was tested for three different flow rates on the model simulating common and extreme flow situations at the weir. The flows were selected to simulate also different hydraulic phenomena at the weir – overflow, outflow, and free overflow. After each flow simulation the scour in the riverbed was measured. The measured scour parameters were depth of the scour, the distance of the deepest point from the existing water structure and the amount of the material carried away. The resulting parameters were assessed with respect to each other for the corresponding flow rates. The best results in scour reduction were achieved for horizontal embankment with the depth of 0 m. The designs with increased depth were causing secondary hydraulic jump in the riverbed which increased the scours. The tested designs of the embankments were able to reduce scour size by up to 45% for the outflow, by less than 20% for free overflow and by more than 80% at the overflow.

Study on flow regime change due to weir construction plan in Batang Asai River, Sarolangun, Province of Jambi

The weir design process not only considers the location, dimensions, strength, and durability of the weir structure, but must also be consider the effect on the flow characteristics in the river after the weir, especially related to the flow velocity characteristic around the weir. The water level will rise and affect the flow velocity downstream of the weir. Because of the fall of water, the velocity will greatly increase and the river can erode. The weir construction on the Batang Asai River, specifically located in Sarolangun, Province of Jambi, has unique conditions that cause the velocity of water after the weir to increase. Several alternatives will be analysed as solutions to deal with changes in flow velocity. The alternatives are groundsill, riverbed normalization, and river crossing widening. It was found that the alternative of river widening showed a significant reduction in flow velocity.