Hydraulic Laboratory Research Articles

Simulation of fully coupled hydro-mechanical behavior based on an analogy between hydraulic fracturing and heat conduction

The hydraulic fracturing process involves complex coupling problems of the deformation and fracturing of solid and fluid flow in fractures. In this paper, a simple numerical tool for simulating the coupled hydro-mechanical behavior is developed by using an analogy between hydraulic fracturing and heat conduction. Using this analogy, the numerical implementation can be simply realized in the framework of a commercial finite element package ABAQUS with two user material subroutines to fully characterize the complex coupling problems of hydraulic fracturing. It is thus considerably simplified without any new development of user-defined element and fluid–solid solver but directly with the commercial finite element package. The proposed numerical tool along with the virtual crack method for elastic–brittle material is firstly verified by the classical 2D plain strain KGD analytical solution and then applied to several representative hydraulic fracturing problems and laboratory tests to illustrate its advantageous features. The present method is aiming to develop a useful numerical tool to study the coupled hydro-mechanical behavior of hydraulic fracturing. However, it is not limited to any specific materials and can be extended to other constitutive models that featured with the fully coupling problems of fluid and solid due to its simplicity.

Предотвращение каскадного развития пожара на тепловых электростанциях Вьетнама на основе применения резервуаров с защитной стенкой и волноотражающим козырьком

PURPOSE. The article, based on the results of an statistics analysis of vertical steel tanks (VST) destruction with flammable liquids, as well as forecasting the situation on the territory of a thermal power plant (TPP) during destruction of a typical VST-20 000 m3 with fuel oil, substantiates the need to use tanks with protective wall (TPW) and a wave-reflecting visor in tank farms at thermal power plants in Vietnam, as one of the promising methods aimed at preventing the possible cascading fire development at the facility or the occurrence of an emergency situation (ES). The main provisions of the method developed on the basis of performed experimental studies have been presented, which establishes the procedure for calculating the geometric parameters of a protective wall with a horizontal or inclined wave-reflecting visor, designed to completely contain the breakthrough wave during the quasi-instantaneous destruction of the main (internal) VST. METHODS. In the process of research methods of similarity theory and hydraulic laboratory modeling, physical experiment, observation, comparison, finding an empirical relationship based on mathematical processing of experimental data, description and generalization have been used. FINDINGS. The features of the location of thermal power plants in Vietnam have been revealed, consisting in their direct location in populated areas or near water bodies. It has been established that destruction of even one large-sized VST with flammable liquid in the tank farm of a thermal power plant can lead to a cascade development of an accident or emergency occurrence. It has been proven that installing a wave-reflecting visor on the protective wall is an effective way to reduce it to or below the maximum liquid level in the main VST, depending on the distance between the walls and the length of the visor extension. RESEARCH APPLICATION FIELD. The developed method, containing calculation schemes and empirical dependencies, can be the basis for the development of a regulatory document to ensure fire safety of TPW, including when they are located on the territory of tank farms of thermal power plants. CONCLUSIONS. The proposed design of the PWT, improved by installing a wave-reflecting visor, will make it possible to design and operate these types of tanks, ensuring the required level of fire, industrial and environmental safety at the protection site, subject to, among other things, the requirements for the stability of the wall and the visor to the effects of liquid flow and the main VST structures that collapse during an accident.

IRREGULAR WAVEMAKER (PISTON TYPE) IN A NUMERICAL AND PHYSICAL WAVE TANK

This paper describes the design and execution of a wavemaker system (piston type) in the Dokuz Eylül University Hydraulic Laboratory flume to perform hydraulic model tests using regular and irregular waves. In this study, we will focus on generating the irregular waves from the target JONSWAP spectrum using an adjusted random phase method; also, the control software of the wavemaker is described. An identical numerical channel wave to the physical flume was modeled to compare and observe the irregular wave profile using Flow 3D, one of the advanced computational fluid dynamics (CFD) software. The paddle movement was validated by comparing the experimental converted irregular wave surface elevations to the wave spectrum to the numerical models of several waves.

A numerical-experimental study on the hydrodynamic performance of a U-OWC wave energy converter

The present work is aimed to the formulation of empirical relationships useful for the design of a U-OWC type marine energy conversion device, with particular reference to the calculation of the resonance index and hydrodynamic efficiency. The study was conducted using physical and numerical modelling. The experimental campaign was carried out within the flume at the Hydraulics Laboratory of the University of Messina. Tests were performed by forcing the model on a scale of 1:30 with the action of several regular waves and varying the geometry of the device. Furthermore, to extend the experimental dataset with more energetic waves and new geometrical characteristics, the physical model was also reproduced numerically using the CFD software OpenFOAM. The validation process of the numerical model showed that the turbulent LES model reproduced the behaviour of the device more effectively than the turbulent κ-ω SST model, particularly for the more energetic waves.The extended dataset (experimental and numerical) was analysed by discussing the dependents of the hydraulic and energetic performance concerning the orifice diameter of the device and the width of the U-OWC vertical duct. It was observed that the combination of such geometrical characteristics resulted in an enhanced effect regarding the performance of the device, particularly the energy performance.

Experimental investigation of sediment movement as a result of homogeneous earth-fill dam overtopping break over a simplified urban area

When an earth-fill dam breaks, dam body sediment and water flow simultaneously move to downstream area causing devastation. Dam break studies in the literature have concentrated mostly on the water flow part while ignoring the sediment movement by designing the dam body as a movable metal gate. This study, however, is the first one experimentally investigating flow and sediment transport due to an earth-fill dam break by constructing the dam body from sediment. Sediment propagation as a result of homogenous earth-fill dam overtopping break was experimentally studied in a laboratory flume of 18.4 m long and 2.0 m wide, and 0.88 m in height in the Hydraulics Laboratory of Izmir Katip Celebi University, Izmir, Turkey. Downstream section right after the dam body was designed as a smooth bed and rough bed. The rough bed, resembling a simplified urban area, was created by using thirteen 10 × 10 × 10 cm sized concrete blocks. The dam body was constructed as homogenous with uniform material having D50 = 0.441 mm. The earth-fill dam body was built using the standard compression methods; each layer of sediment with a thickness of 10 cm was laid in layers, and the body was prepared with a crest width of 10 cm, a transverse base width of 200 cm, a longitudinal base width of 202 cm and height of 60 cm with upstream and downstream slopes of 1:1.6. The water level behind the dam was gradually raised until it overtopped the crest level. A pre-breach was formed at the top of the dam to trigger the break. During each dam break event, water depths were measured by three ULS-40D level meter sensors at different locations, and the final sediment bathymetry map was generated using the ULS-40D Probes at 10 × 10 cm grids. The results showed that, in both smooth and rough downstream bed cases, the dam body eventually collapsed while a great portion of it was carried away by the flood flow. The sediment spreading occurred all over the downstream area, showing significant non-uniform variation in thickness both longitudinally and transversely, especially in the simulated urban area. All the residential areas, while breaking in motion, were submerged under the muddy flow. Some blocks were almost submerged while sediment heights reached half level of some blocks at the end of the experiment. Sediment heights were higher in the urban area.

Numerical and Physical Modeling of Ponte Liscione (Guardialfiera, Molise) Dam Spillways and Stilling Basin

Issues such as the design or reauditing of dams due to the occurrence of extreme events caused by climatic change are mandatory to address to ensure the safety of territories. These topics may be tackled numerically with Computational Fluid Dynamics and experimentally with physical models. This paper describes the 1:60 Froude-scaled numerical model of the Liscione (Guardialfiera, Molise, Italy) dam spillway and the downstream stilling basin. The k-ω SST turbulence model was chosen to close the Reynolds-averaged Navier–Stokes equations (RANS) implemented in the commercial software Ansys Fluent ®. The computation domain was discretized using a grid with hexagonal meshes. Experimental data for model validation were gathered from the 1:60 scale physical model of the Liscione dam spillways and the downstream riverbed of the Biferno river built at the Laboratory of Hydraulic and Maritime Constructions of the Sapienza University of Rome. The model was scaled according to the Froude number and fully developed turbulent flow conditions were reproduced at the model scale (Re > 10,000). From the analysis of the results of both the physical and the numerical models, it is clear that the stilling basin is undersized and therefore insufficient to manage the energy content of the fluid output to the river, with a significant impact on the erodible downstream river bottom in terms of scour depths. Furthermore, the numerical model showed that a less vigorous jet-like flow is obtained by removing one of the sills the dam is supplied with.

Damping transformation modeling on wheel suspension using pneumatic cylinder thrust force as a substitute for vehicle weight

This study aims to produce a vertical dynamic load transformation model, FDV of medium weight vehicles that burden the road structure, the form of suspension work characteristics on vehicle wheels that experience disturbances and vertical loading, and the relationship between vehicle vertical dynamic loads and road structure strength, FA0 in the form of a dimensionless parameter. The experiment was carried out at the Pneumatic and Hydraulics Laboratory of the State Polytechnic of Ujung Pandang using pneumatic actuators as a substitute for vehicle weight. The dynamic load fluctuation of the medium weight category vehicle is equivalent to a pressurized air setting from 1 bar to 6 bar which puts a direct load on the suspension system on the vehicle’s wheels. The deviation, Y (cm) that occurs when there is compression on the Spring and Shock Absorber can be measured using a distance sensor, while the vertical dynamic load, FDV which burdens the road surface using a Load Cell. The data were analyzed using the vehicle dynamic load equation with pressure variable, P2 (bar), spring constant, k2 and damping fluid coefficient, c. A mathematical study of the vibration characteristics of the vehicle suspension was obtained using the Mat Lab program. The results showed that the vibration characteristics of the vehicle body experienced an overshot at a deviation of Y is 0.534 m for 0.131 seconds. The role of the shock absorber in the suspension mechanism can reduce 26.43 % of the vertical dynamic load FDV (N), and in the time interval, t is 3 seconds with acceleration deviation, is 0.25 m/s2 begins to feel comfortable. The relationship between vehicle dynamic load, FDV and road structure strength, FA0 is 0.0178. The data from the comparative analysis is then recommended as a consideration for road construction planners to determine the strength and service life of the road.

Particle saltation trajectories in supercritical open channel flows: Roughness effect

AbstractBed load sediment transport governed by particle saltation in supercritical open channel flows causes bedrock incision in high‐gradient mountain streams and hydro‐abrasion at hydraulic structures. Hence, a better understanding of turbulent flow characteristics and particle dynamics is of prime importance for the prediction of river and landscape evolution, and for a sustainable design of hydraulic structures. To this end, we experimentally investigated single‐particle dynamics in supercritical open channel flows over fixed planar and abraded beds covering smooth, transitionally rough, and hydraulically rough regimes. The experiments were performed at the Laboratory of Hydraulics, Hydrology and Glaciology (VAW) of ETH Zürich in a wide range of hydraulic conditions with various channel width‐to‐depth aspect ratios (b/ho) and Froude numbers (F). We investigated the motions of five particle groups differing in shape, hardness, and diameter. By means of a high‐speed camera, the particle velocities and trajectory parameters—such as hop height and hop length—were determined using particle tracking velocimetry. The results reveal that at least 120 individual particles should be used in the tests to determine sound statistics of particle trajectories. In the present test conditions, the particles are dominantly transported in saltation. The effects of particle properties such as shape and diameter on the particle trajectories are negligible, while the rolling probability of the particles for a given flow condition increases with increasing diameter. Bed roughness was found to be the key parameter having a significant effect on the saltation trajectories and horizontal energy transfer. Hop height, hop length, and particle velocities, as well as horizontal energy transfer, increase with increasing bed roughness. Based on the saltation trajectory data, non‐dimensional equations are developed for each hydraulic regime and used to enhance the saltation–abrasion model of Sklar and Dietrich. The present findings contribute to a better understanding of particle motion characteristics under different hydraulic and roughness conditions, and their effect on the mechanics and prediction of bedrock incision and hydro‐abrasion in three‐dimensional supercritical open channel flows occurring in steeply sloped rivers and at hydraulic structures.

Understanding hydraulic fracture mechanisms: From the laboratory to numerical modelling

The development of fracture networks associated with hydraulic fracturing operations are extremely complex multiphysics processes and there is still no accepted methodology for mapping or realistic recreating such fracture networks. This is an issue especially for modeling purposes, as, ideally, an accurate numerical representation, and subsequent numerical model, should be able to honor the trajectory, type, connectivity, and geometric properties of the complex fracture network generated. This research proposes a novel framework capable of conducting fluid flow numerical simulations based on mapped fracture networks induced during hydraulic fracturing laboratory experiments where a shale sample, under true triaxial reservoir stress conditions, is subjected to fluid injection to mimic a single stage open-hole in-situ hydraulic fracture operation. The resulting post-test fracture network of the shale sample is filled with fluorescent dyed epoxy and subsequently imaged. The images are segmented, and individual fractures are classified based on their geometrical characteristics, as parted bedding planes, opened natural fractures, and newly generated hydraulic fractures. The digital fracture network is numerically represented for fluid flow simulation using a dual-porosity model within the finite volume method. In the numerical reconstruction, fractures are implicitly represented in a set of cells with virtual fracture aperture. The properties of each grid cell are assigned based on fracture classification, and flow between grid cells is explicitly assigned based on the connectivity of the grid cells. Findings show faster fluid drainage parallel to bedding planes (horizontal) than in the vertical direction, indicating strong fluid flow anisotropy. Cited as: Abdelaziz, A., Ha, J., Li, M., Magsipoc, E., Sun, L., Grasselli, G. Understanding hydraulic fracture mechanisms: From the laboratory to numerical modelling. Advances in Geo-Energy Research, 2023, 7(1): 66-68. https://doi.org/10.46690/ager.2023.01.07

Virtual support platform for teaching the civil engineering school’s hydraulics laboratories at uis

El laboratorio de Hidráulica del programa de Ingeniería Civil ofreció un espacio para proponer una estrategia de integración, dentro de un espacio virtual de aprendizaje (EVA), de un conjunto de recursos que soportan los procesos de preparación, ejecución y evaluación de las experiencias de aprendizaje formuladas para el cumplimiento del programa. La implementación del EVA para este curso mediante la plataforma Moodle busca involucrar activamente a instructores y estudiantes en una experiencia de mejoramiento continuo, enmarcada en el nuevo contexto global.

Comparative study of LDA and PIV methods for flow homogeneity measurements

Abstract In the Hydraulic Laboratory of the Department of Hydraulic Engineering, Faculty of Civil Engineering, Slovak University of Technology in Bratislava the distribution of the flow velocity in a shaft intake structure was investigated on a physical model. The homogeneity of the flow velocity distribution in the intakes of turbines has a great influence on the turbine performance. Modern optical methods, particle image velocimetry and laser Doppler anemometry, were used to measure the flow velocity distribution in the model of the turbine intake. The particle image velocimetry method provides a record of the velocity field, while the laser Doppler anemometry method provides an accurate indication of the velocity at a given point. The flow velocity distributions in the examined profiles were measured by the particle image velocimetry and laser Doppler anemometry methods and the results were compared with each other.

Riprap Protection Exposed to Overtopping Phenomena: A Review of Laboratory Experimental Models

There are increasing demands from dam safety regulations and guidelines to upgrade the rockfill dams, especially in Norway where over 180 large rockfill dams are present. To protect the hydraulic structure against overtopping events or leakages, it is important to use defence mechanisms such as a protective layer of riprap on the downstream slope. In this article, we display 9 experimental setups of riprap, conducted at the hydraulic laboratory of NTNU (Trondheim) and subjected to overtopping phenomena with increasing water discharge, until the complete failure of the model. These tests were performed on models with dumped and placed riprap, with or without toe support, with or without the downstream rockfill shoulder, and finally on models with a full dam profile. The models with downstream rockfill shoulder as well as with full dam profiles allowed for throughflow. The model behaviour during these experimental tests is described and discussed, according to their respective critical discharge values and associated failure mechanisms. Limitations are also discussed. The results bring to light the benefit of placed riprap compared to dumped riprap structures. As the results show a placed riprap can withstand a significantly higher overtopping discharge than a dumped riprap. Also, the use of toe support enables a significant increase of resistance against overtopping of placed riprap structures. However, toe supports have not proven any significant improvement in stability for dumped riprap structures. This research also puts forward that dumped riprap undergoes a surface erosion process with smaller slides. Placed riprap undergoes a sliding failure mechanism when unsupported at the toe, and a buckling deformation when supported.

Floodborne Objects Type Recognition Using Computer Vision to Mitigate Blockage Originated Floods

The presence of floodborne objects (i.e., vegetation, urban objects) during floods is considered a very critical factor because of their non-linear complex hydrodynamics and impacts on flooding outcomes (e.g., diversion of flows, damage to structures, downstream scouring, failure of structures). Conventional flood models are unable to incorporate the impact of floodborne objects mainly because of the highly complex hydrodynamics and non-linear nature associated with their kinematics and accumulation. Vegetation (i.e., logs, branches, shrubs, entangled grass) and urban objects (i.e., vehicles, bins, shopping carts, building waste materials) offer significant materialistic, hydrodynamic and characterization differences which impact flooding outcomes differently. Therefore, recognition of the types of floodborne objects is considered a key aspect in the process of assessing their impact on flooding. The identification of floodborne object types is performed manually by the flood management officials, and there exists no automated solution in this regard. This paper proposes the use of computer vision technologies for automated floodborne objects type identification from a vision sensor. The proposed approach is to use computer vision object detection (i.e., Faster R-CNN, YOLOv4) models to detect a floodborne object’s type from a given image. The dataset used for this research is referred to as the “Floodborne Objects Recognition Dataset (FORD)” and includes real images of floodborne objects blocking the hydraulic structures extracted from Wollongong City Council (WCC) records and simulated images of scaled floodborne objects blocking the culverts collected from hydraulics laboratory experiments. From the results, the Faster R-CNN model with MobileNet backbone was able to achieve the best Mean Average Precision (mAP) of 84% over the test dataset. To demonstrate the practical use of the proposed approach, two potential use cases for the proposed floodborne object type recognition are reported. Overall, the performance of the implemented computer vision models indicated that such models have the potential to be used for automated identification of floodborne object types.

Physical and physicochemical characteristics of tomato fruits grown under different irrigation water levels and phosphorus sources and rates

Phosphorus (P) is one of the most limiting nutrients for growth and development of crops, and is important for soil fertility managements, since it affects the quality of fruits. With the hypothesis that different levels of irrigation and phosphorus fertilization interfere in the physical and physicochemical properties of tomatoes, the objective of this experiment was to verify this hypothesis and analyze the behavior of the fruits’ responses. The experiment was conducted in a greenhouse at the Hydraulic and Irrigation Laboratory of the Federal Institute of Education, Science, and Technology of the State of Goiás, in Rio Verde, Goiás, Brazil. A randomized block design was used, with a 4×2×4 split-plot arrangement and three replications, totaling 96 experimental plots. The treatments consisted of four P2O5 rates: 25%, 50%, 100%, and 200% of the recommended rate; two P sources: monoammonium phosphate (MAP) and organo-mineral (OM); and four IWL: 50%, 75%, 100%, and 125% of the field capacity. The fruits were evaluated for longitudinal (FLD) and transversal (FTD) diameters, potential hydrogen (pH), titratable acidity (TA), total soluble solid (TSS) contents, and TSS to TA ratio (TSS/TA). The effect of the interactions between the factors IWL and P rate, IWL and P source, and P rate and source were significant for FLD and FTD, TSS, TA, and TSS/TA. The effects of the interactions between IWL and P rate, and IWL and P source were significant for pH. The MAP source combined with the rate of 25% and IWL of 125% resulted in tomato fruits with larger FLD and FTD. The rate of 25% combined with IWL of 77% and 100% resulted in tomato fruits with higher TSS and pH. The OM source resulted in tomato fruits with higher TA when combined with IWL of 50%, and larger FLD when combined with IWL of 105% and 125%.
 (This article belongs to the Special Issue: Agricultural Water Management in Arid and Semi-arid Regions)

Leakage diagnosis of heating pipe-network based on BP neural network

The leakage of heating pipe-network can lead to serious consequences: the heating quality unable to meet the needs of users, increasing the energy consumption of the heating system and so on. In order to improve the accuracy of leakage diagnosis (LD), this paper regards the LD of the heating pipe-network as a pattern recognition problem relying on the intelligent heating experimental pipe-network system of the hydraulic balance laboratory in Shandong Jianzhu University. Based on the experiment datasets, the model datasets and their cross datasets of the experimental pipe-network, we construct and train a BP (Back Propagation) heating pipe-network leakage diagnosis model (HPLDM) which is used to LD towards the single heat-source branch pipe-network and the double heat-sources with double loops pipe-network. For the single heat-source branch pipe-network, the prediction accuracy of the HPLDM built with the model datasets is 89.31%, 98.51% with the experiment datasets, and 99.70% with the cross datasets. For the double heat-sources with double loops pipe-network, the prediction accuracy of the HPLDM built with the model datasets is 100%, 97.03% with the experiment datasets, and 97.20% with the cross datasets. The experimental results show that the HPLDM based on BP neural network has a higher identification accuracy on the diagnosis of not only leakage location, but also leakage degree of the heating pipe-network. Furthermore, the prediction effectiveness of leakage location is better than that of leakage degree. Meanwhile, the HPLDM has strong generalization ability and some reference significance for the LD of other fluid pipe-network.

Estimation of River Discharge Outside the Regime of Uniform Flow

The flow discharge computation is based on assumptions about the energy grade line slope and the water level to estimate the stream flow with the hydraulic model of Manning's equation. The purpose of this paper is to improve the river discharge prediction using a modified practical Manning's equation for non-uniform but also for uniform flow conditions by using free surface slope, bed slope, friction coefficient and the flow depth. This paper presents an improvement in the integration of the average velocity in gradually varied flows. To validate the modified equation, experimentations have been carried out in the hydraulic laboratory of Ain Temouchent University (Algeria) for 23 flow discharges through two measurement sections; we have got 46 values of the average velocity, the bed slope and free surface slope. The results compare very well with the experimentations. A very good agreement has been found between measured and computed velocities with a coefficient of determination R2 (97.91% for section A and 99.45% for Section B) with the normalized RMSE low than 2.4%. This could be a very useful contribution for the literature. No closer-form of this modified Manning equation is available in the literature.

Effects of Bed Materials to Flow Characteristics on Open Channel and Gradually Varied Flow Simulation Using Genetic Algorithm (GA)

Determination of accurate roughness coefficient was realized necessary for hydraulic parameters estimation in open channel flow. For the purpose this study was planned to carry out on experimental basis in hydraulic laboratory hall of campus itself. In this study, a combination between experimental and numerical models study were carried out to investigate the influence of bed roughness on flow characteristics. Experiments were conducted on six bed materials (Sand, Gravel, Cement plaster, Grass, Formica and cast iron (original bed of channel)) in three conditions. Firstly the discharge was varied at same tail water level. Secondly the depths were varied for same discharge and thirdly the depths were measured for different discharges for each bed material Results were analyzed and were graphically presented .The Manning roughness coefficient was estimated for each bed material using the experimental and discharge optimization technique. The percentages of errors between the observed and predicted were reported. Since the channel represents compound case having glass wall and different bed material, the roughness coefficient of each bed materials were predicted by optimization on genetic algorithm to the lotter’s modified equation in which the exponent alpha value varies from 1.28 to 1.76 The shear stress distribution was examined by first and second approximation theory on smooth rectangular channel on Knight et al (1984) model. It was compared with the experimental average shear stress and was found the first approximation theory over estimated to the experimental value whereas second approximation result was within the average relative error of 1.61% for bed. Side wall/bed stress ration was found of 0.61. Similarly gradually varied flow was simulated in python using optimal value of roughness coefficient.

DEVELOPMENT AND APPLICATION OF WSC AND PARSHALL FLUMES FOR DATA COLLECTION OF SURFACE RUNOFF

The use of spillways, such as Parshall and WSC flumes, are widely used for fluid flow measurement, as in Water and Sewage Treatment Plants, measurement of runoff for agricultural purposes. Thus, it has been used in scientific works in which it is necessary to obtain the flow rate, due to measurement accuracy, ease of construction and operation. Therefore, the objective was to dimension and build flumes like Parshall and WSC, and adjust a mathematical model to estimate the drained flow depending on the height of the depth water in these flumes. The experiment was carried out in the Federal University of Grande Dourados in Hydraulics Laboratory, where flow values for flumes were measured by the volumetric method. The data were subjected to the normality test and regression adjustment for potential function. With the results, a good adjustment of the calibration equation was verified, obtaining high values of determination coefficients for the flumes, WSC (R2 = 0.98) and Parshall (R2 = 0.99), the minimum and maximum flows observed were, respectively, 0.039 and 2.23 m3 h-1 for WSC and 0.11 m3 h-1 e 4.44 m3 h-1 for Parshall, meeting the specifications for use in experimental plots with typical weather of the South region of Mato Grosso do Sul State.

Experimental investigation of flow pattern at 180° bend with rigid bed in effect of twin convergent bridge piers

The generation of vortices in sharp bends of rivers is a well-known phenomenon. However, their influence on the bridge pier has not been investigated deeply. This study studies the flow pattern around the twin convergent bridge pier in a sharp bend by an experimental approach. The test facility includes a channel located at Advanced Hydraulic Laboratory, Persian Gulf University, with a 1 m width and 2 m central radius. The flow 3D velocity is measured along the bend by an ADV velocimeter. It is realized that the most important vortex from a sediment transport point of view is located adjacent to a pier in a plane just parallel to the flow direction. Furthermore, it could be concluded that the pier influencing range has an approximate dimension of 10 times pier diameter in a plane parallel to flow and 3 timer pier diameters in the vertical plane. Results and discussions are presented throughout the paper.

KAJIAN RANCANG BANGUN ALAT UKUR DEBIT AMBANG LEBAR DENGAN VARIASI KEMIRINGAN HILIR

The modeling of broad crested weirs is expected to facilitate understanding, especially the behavior of the flow flowing through the measuring instrument. The flow behavior under consideration is hydraulic behavior, measurement accuracy, and discharge curve. In addition, there is a relationship between discharge and water level upstream and downstream of the spillway, as well as the relationship of the variation of discharge flowing through the broad crested weirs to the loss of energy height. From the results of this study, it was found that there was a relationship between discharge and water level upstream, downstream, water level above the threshold, and energy loss for wide-threshold spillway. The modeling of the broad crested weirs assumes that the Froude number that occurs in the model is the same as the Froude number that occurs in the field. So that the scale of discharge, time, velocity and volume will be able to represent the actual conditions in the field. The scale of length, width, and height of the prototype is 1: 100. The methodology used is to carry out testing in the hydraulics laboratory by varying Q1, Q2, Q3, Q4, …. Qn, to obtain variations in water level upstream and downstream of the broad crested weirs. From the results of the study, it was found that the energy loss was relatively small with a trend of Y = 101.66x2 - 0.7359x + 0.0017 with the slope of the broad crested weirs downstream is 1:2, Y = 467.84x2 - 1.7816x + 0.0022 for slope of the broad crested weirs downstream is 1:1.5, and Y = -1140,4x2 + 0.6383x + 0.0077 with the slope of the broad crested weirs downstream is 1:1 where Y is the energy loss in meters and X is the discharge in m3/sec.