Hydraulic Laboratory Research Articles

Experimental and numerical Investigation of entrapped air presence and expulsions in irregular pipelines on hydraulic transients

In the present study, the transient event of rapid opening of upstream valve in undulated water pipeline with entrapped air pockets was investigated both experimentally and numerically. Pressure peaks and oscillation patterns were traced with the variation of air pocket length, blocking column length and water filling column. A transient two-dimensional CFD simulation model was introduced and validated by laboratory experiments. The proposed CFD model was conducted using ANSYS fluent based on Reynolds-averaged Navier–Stokes (RANS) equations and the volume of fluid (VOF) method. A user-defined functions (UDF) for both water compressibility effect and opening valve estimated pattern were adopted to verify the experimental results. For further understanding of transient response air expulsion through air vents of various orifices diameters were experimentally investigated. Image processing technique by using photoshop were utilized to clarify Stages of air expulsions, air water interaction and orifice flow regime. The obtained results showed that pressure peaks and oscillations depend strongly on orifice size where small orifice caused an intermitted flow choked by water column in contrast to large orifice where water hammer was dominated. An experimental facility was constructed at Alexandria university hydraulics laboratory to fulfil the research objectives. Air presence challenges in hydraulic systems are extensively applied for water and fuel supply lines, firefighting, and drainage systems in airports ground facilities.

Determination of Soil Moisture for Sandy Soils Using Gas and Microwave Ovens

Since there are several methods used to determine soil moisture, the objective was to compare the moisture values obtained with the use of a gas oven and a microwave to the values obtained with the standard oven method. Having been carried out at the Hydraulics Laboratory of the State University of Maringá, Umuarama Regional Campus, the performance of the methods was evaluated in the determination of five levels of moisture (10, 15, 20, 25, and 30%), with dry masses obtained at 15, 20, 25 and 30 minutes for the gas oven and at 2, 4, 6 and 8 minutes for the microwave. The best drying times were selected using the Taylor Diagram. Linear regression was performed between the methods, in order to obtain the correlation coefficient (r), the Willmott agreement index (d), the performance index (c), absolute error (EA), absolute mean error (ERA), and root mean square error (RQME). By analyzing the results obtained, it can be stated that the gas oven method and the microwave method presented excellent performance when compared to the standard method. It was also concluded that the time of 25 minutes for the gas oven method was efficient and, for the microwave method, the drying time of 8 minutes was sufficient, meaning a reduction in the time for moisture determination.

Study on the Manufacturing of Composite Materials Made from Glass Fiber Reinforced Polymer (GFRP) in Indonesia for Use as Lining in Open Channels

This study explained the potential use of glass fiber-reinforced polymer (GFRP) composite materials as an alternative lined material for irrigation channels in Indonesia. Currently, only four recommended materials are used as lining in irrigation channels in Indonesia, i.e., stone masonry, concrete, soil-cement, and ferrocement. Almost all lined material's main constituents are sourced from nature/environment. The exploitation of these mined materials will impact environmental destruction. This study focused on the manufacturing process of GFRP material, GFRP surface roughness testing, and the water flow characteristics in the hydraulic model experimental testing. The manufacturing process of GFRP material used polyester resin as the polymer matrix, E-glass type with a combination of woven roving mat covered by non-woven standard mat as the glass fiber reinforcement, and manufacturing process with a combination of hand lay-up and spray-up techniques. The GFRP material product has an average surface roughness coefficient value of Ra around 5.19 to 5.97 μm. The GFRP manufacturing has a good uniform product, as the average surface roughness coefficients of GFRP material have relatively the same values. It is shown that a factory in Indonesia has sufficient capacity to manufacture GFRP material for lining in open channels. The water flow characteristics in the flume were turbulent during testing in the hydraulic laboratory. The experimental study concluded that the GFRP composite materials could be implemented as preliminary references for alternative lined material in irrigation channels in Indonesia.

Description of the design and construction of a physical model of a dam for educational purposes

The objective of this document is to present the construction process of a physical model that resembles a dam, the use of which allows the reproduction of different hydrological and hydraulic phenomena, for example: flow, pump calculation, pipeline design, flow in open channels, among others. The built physical model has plan dimensions of 2.85 m wide by 11.50 m long, built with 15x20x40 concrete blocks and f'c=100 kg/cm2, 150 kg/cm2 and 200 kg/cm2 resistance concrete, contains PVC pipes of 3” that contribute to the discharge of the flow; It will be part of the Hydraulics Laboratory facilities and impacts the academic development of the Civil Engineering and Administration, Energy Engineering and Mechanical Engineering programs of the Engineering Faculty of the Universidad Autónoma de Campeche.

Discharge coefficients to be used in inlet hydraulics

Urban pluvial floods can be produced or exacerbated by an insufficient density of inlets or by their poor hydraulic efficiency. Therefore, proper consideration of the hydraulic performance of inlets is essential to guarantee the correct functioning of urban drainage systems during heavy storm events. Recent advances in computational analysis in the field of hydrodynamics modelling allow the use of the well-known concept of dual drainage for design and planning purposes by simulating flow transfers between the surface layer (streets) and underground layers (sewers) through a proper hydraulic characterisation of inlet efficiency. Powerful commercial software packages allow simulations of flow transfer and use different approaches and formulas. Many of these approaches include the possibility of treating a sewer inlet as an orifice. In this context, this paper presents a methodology to obtain orifice discharge coefficients for three inlets previously tested at the hydraulics laboratory of the Technical University of Catalonia. Discharge coefficients of 0.18–0.58 were obtained for Froude numbers of 1.12–4.40, quite far from the usual recommended values. The proposed procedure can also be applied to non-tested grates.

Detection of Leakages in a Pipeline Network based on Hydraulic Laboratory Modelling with Artificial Intelligence

Detection of Leakages in a Pipeline Network based on Hydraulic Laboratory Modelling with Artificial Intelligence

USING HYDRODYNAMICS TO IMPROVE SEA STAR FISHERIES IN COASTAL REGIONS

Sea stars (starfish) predate on various shellfish such as mussels and clams, and can have a negative impact on the blue-mussel production and aquaculture. This has encouraged the harvesting of sea stars to protect blue mussels and clams from predation, but they are also targeted commercially, as a valuable protein source used e.g. in animal feed. Towed fishing gears can be used to harvest sea stars in coastal regions, however, little is known scientifically about the hydrodynamics around these gears. To better understand the hydrodynamics around towed fishing gears, an experimental investigation has been carried out in a current flume within the DTU Civil and Mechanical Engineering Hydraulics Laboratory.

INVESTIGATING DREDGE PLACEMENT OPTIMISATION TO BENEFIT SURF AMENITY

Dredge material removed from the Tweed River Entrance is deposited offshore from Gold Coast beaches to assist in mitigating erosion. Research was undertaken by the Queensland Government Hydraulics Laboratory (QGHL), in collaboration with Tweed Sand Bypassing (TSB), to investigate the potential of targeting dredge depositions to also improve surf amenity. A time-domain numerical wave model (SWASH) was developed as a design tool and calibrated using physical model data. Overall, SWASH reproduced wave heights over and in the lee of the mound with reasonable accuracy. However, tuning of the breaking parameters (α and β) is necessary to accurately simulate the onset and persistence of the breaking process. The results of both physical and numerical modelling highlight the importance of sand mound shape in disrupting the wave field, resulting in breakpoint variability in the mound's lee, which could potentially create more favorable surfing conditions.

Experimental and Numerical CFD Modelling of the Hydrodynamic Effects Induced by a Ram Pump Waste Valve

The hydraulic ram pump or hydram is a machine capable of lifting water to a hydraulic head higher than the level of the supply source. It is a sustainable and self-sufficient device: the working principle is based on the rise of abrupt pressure variations occurring in the feeding pipeline when the liquid inside it undergoes a locally sharp change in velocity as a consequence of the sudden closure of the waste valve. Invented in 1772, the pump has been improved over the decades. Due to its simplicity, low cost and reliability, it has been widely used worldwide to provide adequate domestic water supplies, especially before the spreading of electricity and internal combustion engines. In recent years, the new attention placed on sustainability and energy transition from fossil fuels to renewable energy devices has brought a growing interest to this basic machine, essentially forgotten and abandoned in the last century; it seems promising especially in developing countries. The hydram is, in fact, a very simple machine, with only two moving parts, the waste and delivery valves. The efficiency of the hydraulic ram pump is mainly influenced by the characteristics of the waste valve. However, sufficient data are not available for the design of the hydram and the waste valve. In this work, the behaviour of the waste valve of a hydram was simulated by means of Computational Fluid Dynamics (CFD). Velocity and pressure values were analysed for different scenarios with different closing times of the valve. The data obtained from the developed numerical model were compared, in order to verify the validity of the simulations, with those collected during the operation of the hydram placed at the Laboratory of Environmental and Marine Hydraulics (LIDAM) of the University of Salerno, Italy. The numerical model thus obtained can, therefore, be used to identify the ideal configuration of the valve in order to ensure the best performance of the hydram.

A Simplified Experimental Method to Estimate the Transport of Non-Buoyant Plastic Particles Due to Waves by 2D Image Processing

Plastic is one of the most widely used materials. It is expected that there will be about 12 billion tons of debris dispersed into the environment by 2050. This, combined with marine littering, pollution and climate change will threaten our ability to sustainably use oceans, seas and coasts. In this regard, it is important to understand transport mechanisms and predict hotspots of plastic pollution. Physical models are a valid support to achieve such a goal. In this regard, it is necessary to adopt specific techniques which allow the movement of plastic to be monitored. Considering the relatively high size of plastic particles that could be used during experimental campaigns, new approaches based on image processing could be implemented. This study presents a simplified method to estimate the transport of particle debris under sea waves by 2D image processing, avoiding any disturbance of the dynamic field. The proposed method, based on the blob analysis, was implemented and calibrated within the wave flume of the Hydraulics Laboratory at the University of Messina. After a calibration process, the method was used to study the behaviour of the plastic debris under several hydrodynamic conditions. The results obtained in terms of displacement and velocity of the analysed sample showed a great reliability of the used methodology.

A serpent-type wave energy converter

The problem of the interaction of waves with a serpent-type wave energy converter was investigated, and a novel 3D analytical solution was derived. The optimal parameters of the energy converter were derived for the first time from wave energy principles. The results show that the wave power captured by the device increases with increasing wave lengths until a maximum and then decreases. The efficiency increases with decreasing stiffness of the device in shallow and intermediate waters. In deep water, the efficiency increases with increasing stiffness until a local maximum and then decreases. Moreover, the efficiency increases with the increasing mass of the device in shallow and intermediate waters. In deep water, the efficiency of a converter decreases with the increasing mass of the device. An original approach to determine the optimal parameters of a device for given wave conditions was derived. The derived analytical formula shows that the top efficiency level of power capturing cannot exceed 50%. This is the theoretical maximum for this type of converter. The power take-off optimization analysis also identifies the spectrum of wave conditions for which the efficiency of the generator is close to the maximum. A series of laboratory experiments were conducted in a hydraulic laboratory to verify the model. The comparisons of the recorded data with the analytical solution show a very good agreement.

Forces on a Vertical Dam due to Solitary Impulse Wave Run-Up and Overtopping

Impulse waves feature tsunami-like characteristics and are generated by very rapid mass wasting, including landslides and avalanches, into water bodies. In engineered reservoirs, these waves may run up and overtop the dam, thereby exerting hydrostatic and dynamic forces on its structure. For this work, solitary waves were applied as a proxy for impulse waves and the forces acting on vertical structures during wave run-up and overtopping were investigated with hydraulic laboratory experiments. The solitary waves were generated in a wave channel with a piston-type wave generator and the horizontal pressure forces at a vertical wall as well as a vertical dam-like structure were measured with multiple pressure sensors. The discrete pressure data were used to interpolate pressure distributions and the resulting horizontal forces. Empirical equations were derived, approximating the measured maximum forces and their respective centers of pressure within ±7% for both cases with and without wave overtopping. For small freeboards, already small relative wave amplitudes may exert forces similar to those induced by an earthquake as estimated with a pseudo-static approach.

Analisis Distribusi Debit Aliran pada Pelimpah dengan Variasi Model Bangunan Peluncur

Spillway is a structure in a dam designed to drain excess water into a downstream river. The purpose of this study was to determine the water level in the stepped and ladderless chutes and to determine the type of flow that occurs in the stepped and non-stepped chutes. The research method is a laboratory experiment and the data obtained is based on the results of observations made at the Hydraulics Laboratory of the University of Muhammadiyah Makassar. After passing through the launcher building, the water level in the 1st aperture ladder launcher is 2.7 cm, 2.9 cm in the 2nd opening, 2.9 cm in the 3rd opening. The water level in the ladderless launcher at the 1st opening is 3 cm, at the second opening is 3.5 cm, at the 3rd opening is 3.9 cm so that it can be concluded that the shape of the launcher structure influences the water level, thus the water level at ladderless launcher is larger than ladderless launcher. After passing through the launcher building, the Reynolds number on the stepped launcher with the 1st opening is 8301, on the 2nd opening is 8811, on the 3rd opening is 9061. to 3 of 26,103.

Numerical Modelling on Physical Model of Ringlet Reservoir, Cameron Highland, Malaysia: How Flow Conditions Affect the Hydrodynamics

The relative impacts of changes in the storage capacity of a reservoir are strongly influenced by its hydrodynamics. This study focused mainly on predicting the flow velocities and assessing the effectiveness of groynes as control mitigation structures in changes in the water depth and velocity distributions in Ringlet Reservoir. Initially, the physical model of the Habu River (the main part of Ringlet Reservoir) was fabricated, and flow velocities were measured. Then, a two-dimensional HEC-RAS was adapted to numerically simulate the hydrodynamics of the annual recurrence intervals of 1, 5, and 100 years in the Ringlet Reservoir. Experimental data acquired at the Hydraulic and Instrumentation Laboratory of the National Water Research Institute of Malaysia (NAHRIM) was used to calibrate and validate the numerical models. The comparison of simulation and experimental results revealed that the water levels in all simulations were consistent. As for the velocity, the results show a comparable trend but with a slight variation of results compared to the experiments due to a few restrictions found in both simulations. These simulation results are deemed significant in predicting future sediment transport control based on hydrodynamics in this reservoir and can be of future reference.

Optimal hydraulic energy harvesting strategy for PaT installation in Water Distribution Networks

Water Distribution Networks (WDNs) represent a noteworthy field for possible implementation of Small Hydropower (SHP), by replacing Pressure Reduction Valves (PRV) with turbomachines, in particular Pump as Turbines (PaTs), to control and regulate the pressure, while harvesting energy otherwise wasted. Different models were developed to predict the performance and select the positioning of the PaTs for the maximum energy recovery but most of them neglect practical aspect such as: power grid limitations and optimal harvesting strategy. In this framework, we intend to propose a new method to select a PaT, defining its optimal working point, by introducing an energy exploitation coefficient. The proposed methodology is based on the experimental results of a real PaT tested in the high capacity hydraulic laboratory at Polytechnic University of Bari. Firstly, the selected commercial centrifugal pump was tested in both pump and turbine modes. Then, three different approaches, for the Best Efficiency Point (BEP) selection, are described and compared in terms of energy exploitation and capacity factor for a WDN. The first consists of selecting the BEP at the average flow rate, the second one considers the probability distribution of the flow rate and the corresponding available hydraulic energy, whereas the latter is based on the highest energy harvesting. By applying energy production, economic and environmental analyses, the new proposed methodology, based on the third approach, shows a remarkable advantage in terms of exploited energy. Indeed a remarkable 60% energy recovery is achieved with 334 ton CO2/year avoided. Furthermore, the impact of the electrical motor on the maximum power generation (cut-off) is considered. Eventually, useful insights for the future PaT selection and installation are discussed.

A novel and simple passive absorption system for wave-current flumes

The physical limitations of experimental facilities, such as the walls and downstream gate of wave-current flumes, can cause excessive wave reflection. Wave reflection in wave or wave-current flumes is a key phenomenon that often leads to deviations between physical model results and prototype results. If a flume is not equipped with wave absorption systems, either active or passive, in addition to the model’s inaccurate representation of reality, there will be a tendency for the wave paddles to reach the maximum stroke, leading to the abrupt stoppage of the wave generation during the experiments. This research a novel and simple passive wave absorption system in the context of physical modelling studies of scour in the environment of offshore renewable energy technologies. The tests were conducted in the wave-current flume of the Hydraulics Laboratory of FEUP. The results show that the new system reduced the wave reflection coefficient to values within the recommended references for physical modelling studies in offshore engineering. Design hydrodynamic conditions showed reflection coefficients between 11 and 14.5%, and tests without currents revealed reflection coefficients between 7.5 and 10%. This study also highlights how the novel system can easily be adapted to other wave-current flumes and hydrodynamic conditions found in other hydraulics laboratories.

Geometric characteristics of a cylindrical deflector above the end-sill of a stilling basin

ABSTRACT The authors investigated the effect of the cylindrical deflectors over the end sill on minimizing or eliminating scour downstream of a stilling basin. Three different deflector parameters were investigated experimentally to determine the best performance: diameter, vertical placement above the end sill, and lateral position. A physical model was constructed and data were collected at the hydraulic laboratory of the University of Tabriz. The preferred vertical position above the end sill and optimal lateral location that gives the preferred performance of the deflector (minimum – scour) were determined to equal 0.85z and 0.5z (where z is the high of the end sill), respectively. The preferred deflector diameter was determined by installing the deflector at the preferred lateral and vertical locations. The preferred deflector diameter was determined to be 0.5z. Finally, a deflector with the preferred diameter was studied at the preferred location for Froude numbers from 4–8. The results showed that using a cylindrical deflector with the appropriate diameter in the appropriate location can reduce scour depth and length by 78% and 68%, respectively. Finally, based on the dimensional analysis, a relationship was presented to estimate the maximum relative scour depth downstream of a stilling basin with a cylindrical deflector.

How to build vegetation patches in hydraulic studies: a hydrodynamic-ecological perspective on a biological object

Vegetation in freshwater and coastal ecosystems modifies flows, retains sediment, protects banks and shorelines from erosion. Hydraulic laboratory studies with live vegetation or artificial plant mimics, or numerical models with abstracted patches, are often used to quantify the effects of vegetation on water flow and sedimentation. However, the choice of plant and patch characteristics is often not supported by field observations of patch dimensions, density or spacing between consecutive patches. The discrepancy between plants in natural conditions and in flume experiments or numerical studies may affect the relevance of these findings for natural ecosystems. In this study, we provide guidelines for building realistic vegetation patches in hydraulic studies. We collected data on four species of fully submerged freshwater aquatic macrophytes that can grow into well-defined patches. We considered three relevant levels: individual plants (inside patches), isolated patches and multiple neighbouring patches. At the plant level, we observed significant differences in biomechanical traits (Young’s modulus, flexural stiffness), resulting in stem Cauchy numbers ranging from 85.25 to 325.84, and leaf Cauchy numbers from 163.81 to 2003.97. At the patch level, we found significant relationships between patch length, width and height, showing covariation among different patch characteristics. The relationships among patch dimensions differed significantly among sampling sites for three of the four species, suggesting high intraspecific variability in patch sizes. By providing a first set of guidelines for choosing correct and ecologically relevant plant characteristics, this dataset aims to improve our understanding of the complex processes occurring inside and around submerged vegetated patches.

Fuzzy Pressure Control: A Novel Approach to Optimizing Energy Efficiency in Series-Parallel Pumping Systems

Automation and control systems are constantly evolving, using artificial intelligence techniques to implement new forms of control, such as fuzzy control, with advantages over classic control strategies, especially in non-linear systems. Water supply networks are complex systems with different operating configurations, uninterrupted operation requirements, equalization capacity and pressure control in the supply networks, and high reliability. In this sense, this work aims to develop a fuzzy pressure control system for a supply system with three possible operating configurations: a single motor pump, two motor pumps in series, or two motor pumps in parallel. For each configuration, an energy efficiency analysis was carried out according to the demand profile established in this case study. In order to validate the proposed methodology, an experimental water supply system was used, located in the Laboratory of Energy Efficiency and Hydraulics in Sanitation at the Federal University of Paraiba (LENHS/UFPB).

Experimental study of effect of creating an additional cycle along the lateral crest of the labyrinth weirs

One of the practical and economical ways to enhance the discharge capacity is to use labyrinth weirs. The longer crest length in labyrinth weirs than in linear weirs has caused these weirs to have both a higher discharge coefficient and water discharge capacity than a linear weir. In the present study, the discharge coefficient of trapezoidal and triangular labyrinth weirs was investigated by creating an additional cycle along the lateral crest of the weir. By constructing 10 physical models of labyrinth weirs, tests were performed in the hydraulic and sediment laboratory of the Khuzestan Water and Power Authority (KWPA). Dimensional analysis by the Buckingham method revealed the discharge coefficient (Cd) as a function of variable parameters such as the total hydraulic head to weir height ratio (Ht/P) and weir shape factor (Sf). The results of experimental tests showed that at the hydraulic head ratio (Ht/P) of 0.1, the TP weir had a higher discharge coefficient of 3.5% than the TPTPO weir and 2.5% than the TPTRO weir. However, at a hydraulic head ratio of 0.12, the TR weir had a lower discharge coefficient of 4.6% than the TRTPO weir and 6.9% compared to the TRTRO weir. For the hydraulic head ratio of 0.14, the TRTPI weir was 5.8% and the TRTRI weir was 9.4% higher than the TR weir. Statistical analysis using SPSS indicated that TRTPO and TPTRO weirs had the highest correlation with the cubic model.