Hydraulic Head Loss Research Articles

Implications of the operation of continuous granular activated carbon filters on the effluent quality.

Granular activated carbon (GAC) filtration is a commonly used method for advanced wastewater treatment. Filters can be operated continuously or discontinuously, with continuous operation not requiring feed flow interruption for backwashing and circulation (B/C). This study investigated the influence of B/C on the effluent quality of continuous filters. Two continuous GAC filters were operated for 1.5 years, with analysis of dissolved substances and particulate matter in the influent and effluent. The results indicated that various B/C modes had no impact on the removal of dissolved organic carbon and organic micropollutants (OMP), achieving an OMP removal of over 70% after 5,600 treated bed volumes (m3 treated wastewater per m3 GAC). However, it was evident that continuous B/C over 2-4 h resulted in increased turbidity, total suspended solids over 30 mg/L and total phosphorus concentrations of 1.3 mg/L in the filter effluent. Additionally, the study demonstrated that longer and more intensive B/C processes resulted in GAC size degradation with AC concentrations of up to 6.9 mg/L in the filter effluent, along with a change in GAC particle size. Furthermore, the importance of pre-filtration in reducing particulate matter in the filter influent and decreasing hydraulic head loss could be demonstrated.

A theoretical model for predicting the startup performance of pumps as turbines

Using the unsteady Bernoulli equation for the piping system and the angular momentum equation for the rotor, derives here a theoretical model to predict the startup performance of a pump as turbine (PAT). This model is effective for predicting the instantaneous evolution characteristics of the main performance parameters of PAT during startup, and these changings are initially faster and then slowly as a whole. The effect of the rotor moment of inertia and the final stabilized rotational speed of PAT on evolution characteristics of parameters is opposite. The rotational speed, head, hydraulic power, and conversion efficiency show a upward rising trend with the startup time, whereas the flow rate and hydraulic head loss display a downward trend.

Increase of oil product pipeline throughput capacity by means of an anti-turbulent additive

The need to increase the capacity of the pipelines is increasing with the growth of oil and gas production in Russia. Russian and foreign scientists, who carry out numerous experiments and develop additives to oil and petroleum products that reduce hydraulic resistance and head loss from friction in the near-wall area of the pipeline, are working to solve the problem of oil pipeline capacity [1]. This paper considers the actual task of increasing the throughput capacity of oil product pipelines by the use of antiturbulent additive “CDR” and “M - FLOWTREAT” [2]. In the course of solving the task: an analytical review of methods to increase the throughput capacity of pipelines was carried out; a mathematical model of the additive effect on the conditions of oil flow in the pipeline was constructed; the effect of the additive on hydraulic resistance and oil flow velocity was investigated; a comparative assessment of the effectiveness of different additives on the throughput capacity of oil pipelines was given; the optimal concentration of the antiturbulent additive was selected [3]. The mathematical model proposed in this work, taking into account hydraulically smooth pipes and limitation, gives good results of capacity increase of up to 20%. Also, during the research it was found that the additive “M - FLOWTREAT” is more effective than “CDR” and from the point of view of capital investment is more favorable as to achieve the required performance, the amount of the additive is required less [4].

Micro-hydropower systems for smallholder farmers in rural communities of Taraba state, Nigeria: Feasibility study, system analysis, design and performance evaluation (Part II)

This article deals with the feasibility study, system analysis, design, and performance evaluation of micro-hydropower systems for smallholder farmers in rural communities of Taraba state in Nigeria. The hydrologic data used to determine the available flow rate to produce the required hydraulic power were obtained from GEO Global Water Sustainability (GEOGloWS) Service. The principle of Darcy and Weisbach, applied in the Colebrook and Haaland’s equations were employed to analytically estimate the hydraulic head loss due to friction in the penstock, installed trash rack, and fitted valves. The Hydro-Power Plant (HPP) Design professional tool was used to size the different constituents of the proposed micro-hydropower plant, and to evaluate its overall performance. With a low net head of 5.2 m, and a maximum discharge of 1.21 m3/s, two vertical Kaplan turbines with combined peak power of 106 kW were obtained. The Kaplan turbines drive two 6-pole, 50-Hz asynchronous generators with nominal power of 50 kW each. The simulation results from the HPP design tool show that the system achieved a minimum efficiency of 56% with the flow ratio of 0.2, and maximum efficiency 86.1% with flow ratio ranging from 0.6 to 0.8. The Renewable Energy Project Analysis Software (RETScreen) Expert was utilized to perform cost, cash flows, financial sensitivity, and risk analysis of the proposed micro-hydropower plant in Wurno-Gassol. The RETScreen Expert estimated the risk level is at 10%, with minimum and maximum levels of confidence on risk associated with equity payback to occur in 4.6 years and 13.2 years respectively, with median level of confidence in year 7.2. Furthermore, the risk level on energy production cost is estimated at 10%, with minimum and maximum levels of confidence sitting at 101 USD/MWh and 140 USD/MWh respectively, with the median level of confidence at 118 USD/MWh.

Study on the risk of seepage field of Qiantang River underground space excavated in water-rich rheological rock area

Abstract With the rapid development of underwater space construction, the theoretical research is at the initial stage. At present, the theoretical research methods mainly include mirror image method and conformal transformation method. At present, almost all the research objects in analytical research are homogeneous soil layers. However, in practical engineering, soil layers are often distributed in layers. In this study, the seepage field of layered soil layers is analyzed, and the analytical derivation method of seepage field in heterogeneous media based on traditional conformal transformation method is given, which is verified by numerical simulation. The hydraulic head loss of the medium with better permeability in shallow layer is very small, and the streamline is vertically distributed. In the weak interlayer, the hydraulic head loss is huge, and the streamline bends greatly, showing a strong horizontal distribution and converging towards the center. It can provide theoretical basis for the design of water and soil pressure in practical engineering.

Comportamento hidráulico de registros utilizados em instalações hidráulicas prediais

ABSTRACT This study was developed with the objective of evaluating the steady-state hydraulic behavior of gate, ball, and pressure valves with nominal diameters of ½” and ¾”, which are widely used in building water supply networks in Brazil. For this purpose, tests were performed to determine the head loss in ten different valves in four openings with five replicates. A hydraulic head loss testing apparatus was set up in a pipeline network that allowed for the control, monitoring, and acquisition of data. Mean values of the K coefficient of the minor head loss and the equivalent length were estimated for the conditions evaluated. The results were analyzed using box plots, correlation, principal components analysis, and hierarchical clustering. In general, the gate valves showed lower head loss for all the relative openings considered, while the pressure valves showed the greatest head loss. Of the clusters formed, for the second group, there was a predominance of treatments with pressure valves, which showed similarity in terms of the values of the hydraulic variables due to the geometry and construction of the valves.

Vibration control of floating offshore wind turbine using semi-active liquid column gas damper

Floating offshore wind turbines (FOWTs) are becoming an essential instrument for energy generation worldwide. Specific environmental conditions at sea have led to unwanted vibrations and excessive displacement in floating wind turbines, which reduce the performance of these systems. This study aimed to evaluate the effect of semi active liquid column gas damper (SALCGD) on controlling the vibrations of a FOWT under different loads with wave and wind. Variable hydraulic head loss coefficient and variable frequency were used in this study, as well as DBG, VBG, and Bang-Bang algorithms. An analytical model was developed to analyze the dynamic response of the joint wind turbine and damper system, and a time history analysis was performed in the SIMULINK/MATLAB simulation environment. The results indicated that the SALCGD could reduce the displacement response of the pitch degree of freedom in platform in both semi-activation methods. In addition, the performance of each control algorithm varied according to the loading conditions. The effect of SALCGD and TLCGD (tuned liquid column gas damper) was compared in controlling the vibrations of the wind turbine system. According to the results, the superiority of using a semi-active damper was revealed in control.

Estimating Energy Efficient Design Parameters for Trash Racks at Low Head Hydropower Stations

Trash racks are usually composed of an array of bars installed in a hydropower scheme to safeguard the turbines by collecting water-borne detritus. However, current design approaches for the design of trash racks focus on structural criteria. A little attention renders the proper evaluation of hydraulic criteria, which causes a significant hydraulic head loss in low head hydropower schemes with an integral intake. This study investigates the head loss through trash racks by employing computational fluid dynamics (CFD) for several design combinations. A three-dimensional model of trash racks using fractional area/volume obstacle representation (FAVOR) method in FLOW-3D is set up to define the effects of the meshing on the geometry and several simulations are carried out considering various approach velocities and different bar spacings, inclination angles, and blockage ratios. The results indicate that head loss increases with an increase in approach velocity, the inclination angle of the rack with channel bed, and blockage ratio. It is noticed that a clear spacing between vertical bars greater than or equal to 0.075 m has a minimum head loss before it becomes significantly high for lower spacing. In addition, the head loss coefficient increases for screen angles greater than 60°, which can be considered as an optimal parameter for design purpose.

Determining the Flow Resistance of Racks and the Resulting Flow Dynamics in the Channel by Using the Saint-Venant Equations

Racks retain debris in wastewater treatment plants and shield sensitive machinery in numerous engineering applications. In open-channel flows, racks impound the upstream water level by posing local obstacles in the flow. Based on experimental investigations, empirical approaches usually predict the flow resistance by relying on Bernoulli’s energy principle. Since this principle does not correctly consider downstream conditions such as submerged flows, we present a more accurate workflow to determine the flow resistance based on the Saint-Venant equations. We will demonstrate how the loss coefficient and the hydraulic head loss are determined more reliably without adding complexity to the engineering realisation. In contrast to relying solely on two cross-sections with Bernoulli’s energy principle, applying the Saint-Venant equations enables determining the flow depth profile and the flow velocity in the entire channel. This workflow additionally allows predicting the channel’s hydraulic capacity and freeboard in arbitrary applications.

Numerical Analysis of Seepage Failure Modes of Sandy Soils within a Cylindrical Cofferdam

Soil seepage failure within cofferdams is a dangerous phenomenon that always poses difficulties for designers and builders of excavations in zones with high water levels. When the hydraulic head difference H between the upstream and downstream sides reaches a critical height, the downstream soil seepage failure occurs. Depending on soil properties, soil-wall interface characteristics, and cofferdam design, different seepage failure modes can be observed: heaving, boiling, liquefaction, or failure by reduction of the passive earth pressure. In the literature, there are differences, sometimes very large, in the critical value of the hydraulic head loss Hc/D inducing seepage failure given by several methods proposed for stability verification. Then, complex cases are generally approached using simplifying assumptions and adopting large safety factors to take account of uncertainties. In practice, geotechnical engineers deal with many kinds of excavations and different shapes of cofferdams, such as rectangular, square, or circular, which generate three-dimensional (3D) flow conditions. Axisymmetric seepage flow through the soil in a circular cofferdam is often used to model such 3D seepage flow. In this paper, using the numerical code FLAC, several numerical simulations are carried out in axisymmetric groundwater flow conditions to analyze the seepage failure modes of cohesionless sandy soils within a cylindrical cofferdam. The effects of the cofferdam radius, internal soil friction, soil dilatancy, and interface friction on the Hc/D value and failure mode are studied. The numerically obtained seepage failure modes are presented and discussed in various scenarios. The present results, illustrated in both tables and graphs, show a significant decrease in the value of Hc/Dinducing seepage failure, with a decrease in the cofferdam radius. They also indicate the sensitivity of the seepage failure mode to internal soil friction, soil dilatancy, interface friction, and cofferdam radius. As well, new terms are proposed for the seepage failure mode designations based on the 3D view of the downstream soil deformation. Doi: 10.28991/CEJ-2022-08-07-06 Full Text: PDF

Assessing the Potential Resistance of Floating Vegetations Against Different Flow Rates

Constructed floating wetlands (CFWs) have been rising an innovative and environment-friendly water treatment technology for both stormwater and wastewater over the decades. For the sustainability of these systems, hydraulic components of wetland should be very well monitored and managed. This study examined the root resistance of Baumea rubiginosa (PA) and Phragmites australis (PB) grown in normal drinking water and a synthetic water mix representing stormwater and domestic wastewater with low and high nutrient content against different flow rates. With the nutrient uptakes from intermediate bulk container (IBC) water tanks, two plant species had reached at harvest stage over the period of 35 weeks, and then they were subjected to flume test experiment. Two plant species from five different water types showed different growth levels in roots and shoots, and thanks to their stronger and denser root structures, plant species of PA and PB in domestic wastewater with low nutrient were found more resistant to the flow by pushing water deeper and cause a higher hydraulic head loss between upstream and downstream in comparison to the rest of plant types. The relationship between three different components root volume, flow rate and head loss was also analysed through correlation test in SPSS and the relationship between root volume and head loss was found positive at the higher flow rate(s). The results demonstrate that these native plant species in CFWs could be used to reduce extreme flow rates in upstream side and provide a safe environment during extreme flood events.

Диаграммы производительности судовых вакуумных рыбонасосных установок

The article presents the analysis of performance diagrams of marine vacuum fish-pumping units based on Ocean Master water-ring compressor machines published in the domain by Samson Pumps. The diagrams represent the dependence of the flow rate of the water-fish mixture on the given level difference at different values of the rotor speed for two stages of the plant operation. These experimental dependences are well approximated by 3rd-order polynomials over the entire range of acceptable argument values. The calculation of the values of the adjusted determination indices showed that at a rotor speed of 20 s-1 or more the degree of the polynomial can be reduced to the second power. Contour graphs of the performance of vacuum fish pumping units at each stage of their operation were constructed. The argument values for a given feed can be determined from these graphs. They allowed to set the scope of arguments in which the unit would not work. The formula for the performance of vacuum fish pumping units for the full cycle of operation is obtained on the basis of regression models. The maximal performance of the investigated vacuum fish-pumping units indicated in the technical documentation refers to the individual stages of their operation. The performance for a full cycle of work in real conditions can be 5-10 % of the maximum. The obtained analytical expressions can be used in the practical application of performance diagrams of vacuum fish-pumping units, taking into account the hydraulic head losses in the pipeline.

The hydraulic characteristics of Roman lead water pipes: An experimental investigation

An experimental investigation was conducted on two lengths of Roman lead water pipe excavated near Corbridge, Northumberland, England. The pipes date from approximately AD 80. One length of pipe contained a sleeve joint. The pipes were linked to a pump system using 3 D-printed connectors, and the hydraulic head loss along the pipe was measured. The pipe without a joint was used to determine a value for the wall roughness height, fitting the results to the Darcy-Weisbach equation. The wall roughness height obtained was assumed to apply to the pipe with the joint, and the additional head loss observed was then assumed to be due to the joint, allowing determination of a local loss coefficient. The pipes have a sinter encrustation, indicating that they had typically flowed partially full. Using this as an indication of water depth and deriving topographical information from the excavation report, the likely flow the pipes carried during their operational life was estimated. It was concluded that the pipe wall roughness coefficient ks was 0.9 mm, the joint local loss coefficient was 1.159, and that during operation the pipe probably carried around 17 litres/minute.

A Capillary Model for Predicting Saturated Hydraulic Conductivity of Ion-Adsorption Rare Earth Ore Based on Improved Kozeny–Carman Equation

During the in-situ leaching process of ion-adsorption rare earth ore, the seepage velocity of the leaching solution is one of the core problems in studying the leaching efficiency. The determination of the saturated hydraulic conductivity is of great significance to reveal the leaching process. The classical Kozeny–Carman (KC) equation is widely employed to predict the hydraulic conductivity of sandy soils. However, in the equation, the effect of tortuosity on the hydraulic conductivity is not considered, and the specific surface area is difficult to determine in practice. In this study, the capillary model for predicting the saturated hydraulic conductivity of ion-adsorption rare earth ore was established. First, we assumed that all the pores in the ore body are a series of parallel and tortuous capillaries with equal diameters. Based on the assumption and Hagen–Poiseuille’s law, the KC equation was improved by introducing the tortuosity. Second, the constant head permeability tests were carried out to derive the seepage velocity and hydraulic head loss under the steady seepage state. According to the experimental results, the diameter of the capillary was calculated with Darcy's formula. Then we obtained a linear-fit relationship between capillary diameter and porosity to express the specific surface area variation with porosity. Third, by validating with experimental data, when the pore shape coefficient is 0.4, the saturated hydraulic conductivity calculated by the capillary model is in good agreement with the tested value. The proposed model can be considered to have a satisfactory capability to predict the saturated hydraulic conductivity of ion-adsorption rare earth ore.

Design of a column test bench for the evaluation of alternative absorbent materials in wastewater treatment

One of the most used processes for wastewater treatment is filtration, still having unknowns related to the new possible absorbent materials which can provide better pollutant removal. This project proposes a column test bench capable of working with different materials, particle diameters (> 0.35mm) and densities and densities with three columns of 1.5 m length and 4 inches of diameter.. To perform this project, the type of reactive material for the filter medium was identified, considering the nominal and critical size of the fine sand (0.35m), as a basis for determining the design of the length, diameter of the and thickness column. The design conditions were taken so that the hydraulic system can function as a slow and rapid filter. The most critical operating conditions were selected, Qmax: 16.72 lpm and Filtration Rate: 19.80 m / h. Under these operating conditions, a hydraulic head loss of 2.77 m was obtained within the sand column. The result of this research is the design of a column test system that can work under different hydraulics conditions and absorbent materials with sizes greater than 0.35 mm, intended for the investigation of wastewater treatment from car washers and the removal of heavy metals. The final cost of building the column test is about 25% of the commercial price system.

Turbulent Flow between Concentric Rotating Cylinders.(Dept.M)

The turbulent flow between concentric cylinders both rotating in the same or opposite directions is investigated theoretically. A finite difference scheme is developed to solve the boundary layer equations covering the flow. A two-equation model of turbulence was employed in this study. Modifications have been made to the model to take into account the effect of rotating on of the cylinders and the existing of the wall. The effect of changing the radius ratio, axial Reynolds number and angular velocity ratio on the hydraulic friction head loss of air is studied . Distributions for axial mean velocity, tangential mean velocity, turbulence intensity and shear stress in both the entrance region and fully developed region are predicted, also. Comparisons of the present numerical results with other investigators results show good agreement.

An experimental investigation on fish guidance structures with horizontal bars

Horizontal bar racks are successfully used to protect downstream migrating fish and guide them to a bypass at a number of hydropower plants. However, there is no systematic study available on the hydraulic performance of such fish guidance structures. To fill this research gap, we experimentally investigated scale effects and hydraulic head losses of horizontal bar racks. The study involves two main rack angles, two bar shapes and depths, and three bar spacings as primary parameters characterizing the structure investigated as well as top, top & bottom, and bottom overlays as secondary parameters. The bar spacing was the most important factor determining the flow–rack interactions, followed by the rack angle, bar shape and depth, respectively. The overlay positions at the rack resulted in three distinct flow–rack interactions. A new head loss prediction formula was developed and compared with literature data. Recommendations for the optimum and economic rack design are given.

AN ALTERNATIVE FOR ENERGY CONSUMPTION REDUCTION IN DRIP IRRIGATION

The energy consumption in drip irrigation systems as well as in the other irrigation techniques and technologies is an important indicator and an essential part of the operating costs. In contrast to the other irrigation techniques, the irrigation water runoff is smaller because of the fact that only part of the soil surface around the plants is wetted. Nevertheless, taking into account that in most cases the working head in the drippers is 10 m, and there are hydraulic head losses in conducting network, losses in the filters and accessories in the network, then the working head at the beginning of these systems reaches comparatively high values – 35 - 45 m. Taking this into consideration, the author suggests for the first time a new technical solution aimed at the reduction of the working head in the drip laterals and drippers, and more reliable operation of the drip irrigation systems. By now, all companies producing systems for classic drip irrigation in the world offer drip laterals with built-in single and similar nozzles drippers with a long path of the water at the point of water supply, the drippers being of two types-cylindrical and flat. The essence of the suggested solution is that instead of single drippers at the water supply point polynomial drippers are suggested to be built-in, also with a long path of water, consisting of several, located one after another, smaller drippers, connected between each other with a flexible tie (like a chain), both in the cylindrical type and in the flat type. Besides the energy consumption reduction, the new solution features other advantages as well: realization of a larger wetted area of the soil contour and consequently, wetted volume due to the disconcerted water supply at several points of the polynomial dripper; increasing the working flow rate of the drippers for minimum growth of the pressure in them, and a lower probability for termination of the water supply in case of clogging of some of the nozzles drippers; the time for irrigation is reduced.

DESIGN OF WETLAND SYSTEM FOR WASTEWATER QUALITY IMPROVEMENT AT FORMOSA HA TINH STEEL COMPANY

After a marine life disaster in central Viet Nam in 2016 due to poorly treated steel industry wastewater and pipe cleaning solutions, the Formosa Steel Corporation has been improved their wastewater treatment systems. Besides, an effluent polishing and buffer pond – wetland system has to be built. The study team has run the 500 m2 pilot wetland aiming to figure out optimum design parameters such as: balancing requirements of hydraulic conductivity, hydraulic headloss, filtration efficiency and plant growth. The pilot wetland was filled with different kind of lime stone, peanut gravel and sand, running with flow rate 49.5-122.4 m3/h. The pilot test results have provided appropriate design parameters for the 4.3 ha Formosa wetland: Subsurface flow constructed wetland cells CB1, CB2, CB3 placed in series, with maximum horizontal flow rate 122 m3/h, unit hydraulic headloss 22.8cm/100m, followed by free water surface flow wetland cell CB4. The main filtration media selected for wetland cells CB1, 2, 3 was lime stone with diameter 50-100 mm (60 cm depth), where supporting layers for plant vegetation were coarse sand (20cm depth) and peanut gravel of 5-10 mm diameter (10 cm depth). The full scale 10 ha pond-wetland system now is in operation, proving design configurations of the team.

Performance evaluation of a municipal water distribution system using WaterCAD and Epanet

Abstract Population explosion in urban settings usually exerts enormous pressure on existing water supply systems. The result is that overall water demand is usually not satisfied. This study evaluated the performance of Wadata sub-zone water distribution system with respect to pressure, velocity, hydraulic head loss and nodal demands using WaterCAD and Epanet. There was no statistical difference between the results of Epanet and WaterCAD, however, Epanet produced slightly higher results of pressure and velocity in about 60% of all cases examined. About 19 percent (18.52%) of the total number of nodes analyzed had negative pressures while 69 percent (69%) of the nodes had pressures less than the adopted pressure for the analysis. These negative pressures indicate that there is inadequate head within the distribution network for water conveyance to all the sections. About 88 percent (87.7%) of flow velocities in the pipes were within the adopted velocity while around 12 percent (12.3%) of the velocities exceeded the adopted velocity. These excess velocities are partly responsible for the leakages and pipe bursts observed at some points within the system. The results in this study revealed that the performance of the water distribution system of Wadata sub-zone under current demand is inefficient.