Total Head Loss Research Articles

Quantification of energy losses at a surcharging manhole

Hydraulic models of sewer systems are commonly used to predict the risk of urban flooding. However, suitable calibration datasets in flood conditions are scarce. The quantification of energy losses within manhole structures is a current source of uncertainty within such models. To address this gap, a scaled physical manhole model is used to quantify hydraulic energy losses during surcharging and non-surcharging conditions. Two different novel configurations were tested; (1) With and without the presence of a manhole lid; (2) With and without the presence of a shallow flow on the surface. Results showed that total head losses were found to increase in surcharging conditions. The presence of the lid also marginally increased total head losses. The datasets are used to assess the performance of a numerical urban flood model (SIPSON) and comparisons highlighted that SIPSON tends to overestimate energy losses in surcharging conditions.

Minor losses in start connectors of microirrigation laterals

Fittings called start connectors are usually employed to attach each lateral to its corresponding manifold in microirrigation systems. The protrusion of start connectors’ barbs into the manifold induces pressure losses due to contraction and subsequent enlargement of streamlines. In addition, when water flows from a manifold toward a lateral through a start connector, a sudden contraction followed by expansions of flow streamlines cause pressure loss whose intensity is influenced by connector’s geometry. Minor losses along manifolds or at laterals inlet due to start connectors may be significant and might be considered on subunits design or while undertaking hydraulic simulations. The objectives of this research were: (a) to develop equations based on dimensional analysis to estimate minor losses due to start connectors; (b) to compare the accuracy of the developed models against models that are currently used for estimating minor losses; (c) to undertake simulations to assess the relevance of minor losses due to start connectors in hydraulics of subunits. Minor losses due to start connectors were separated into two components. A model was developed and validated to estimate minor losses due to the protrusion of start connectors inserted along a manifold. Two models were developed and validated to estimate minor losses that occur when water flows from a manifold into a lateral line through a start connector. The required data to develop and validate the models were obtained experimentally in laboratory. Although minor losses due to start connectors represented a relative small percentage of total head losses, such effects may be significant while undertaking rigorous hydraulic simulations that require accurate estimation of pressure losses.

Flow regime and head loss in a drip emitter equipped with a labyrinth channel

Labyrinth channels are widely adopted in emitter designs to regulate the water flow. The flow regime and the head loss of labyrinth channels have significant impacts on the hydraulic performance of emitters. In this study, the flow behavior of water passing through an emitter channel is observed using the micro particle image velocimetry (PIV), and the head loss during the flow is analyzed for an emitter with a triangular labyrinth channel. The results show that the flow regime is consistent with the classical theory of hydraulics governing straight channels, even when the cross-sectional area is very small (as small as 0.5 mm×0.5 mm). The critical Reynolds number from laminar to turbulent flows in a labyrinth channel is approximately in a range between 43 and 94. The local head loss factor decreases as the Reynolds number increases for labyrinth channels with smaller cross-sectional areas, such as 0.5 mm×0.5 mm and 1.0 mm×1.0 mm. The local head loss factor is not related to the Reynolds number and is only a function of the boundary conditions of the labyrinth channel when the Reynolds number exceeds approximately 1 000 (for cross-sectional areas of 1.5 mm×1.5 mm and 2.0 mm×2.0 mm). The ratio of the local head loss to the total head loss (▪) first increases and then remains nearly constant as the Reynolds number increases in the labyrinth channel. The head loss in the labyrinth channel is almost equal to the local head loss, (▪) and is approximately 0.95 for cross-sectional areas of greater than 1.0 mm×1.0 mm. These results can be used for optimizing the design of emitter channels.

IRRIGATION EFFICIENCIES OF SUGAR CANE YIELD UNDER DIFFERENT FURROWS LENGTHS IN UPPER EGYPT

The research field experimental work was conducted at the farm of El-Mattana Research Station of the Agricultural Research Center, Luxor Governorate, Upper Egypt during growing season 2012&2013 in clay soil on sugarcane crop. The objective of the herein research trial are to study surface irrigation system performance through using gated pipe system technique under different furrows irrigation lengths treatments L125 (125m) L100 (100m). L75 (75m) and land slope 0.1 % comparing with the traditional irrigation methods under the same condition and treatments. The consequent effects of applying such methods on advance, recession and opportunity time, total water applied, yield, water application efficiency and water use efficiency for sugar cane was considered. The Results showed that the total head losses due to friction was increased gradually until reached 8.4% of the original pumping pressure head measured. The flow variation through 18 meters apart of the gated pipe system was about 13.9 %. Therefore the uniformity distribution of flow through outlets along the gated pipe system was about 86.1 %. On the other hand pressure head variation was about 9.42 %. The result revealed that the traditional methods received more amounts of irrigation water than gated pipe system in the three cases of furrow lengths. The highest values water saving were achieved by using irrigation gated pipe technique with leveling by laser technique 0.1% slope. The traditional irrigation (T1) gave lower water application efficiency than irrigation using gated pipe system (T2) The maximum value of sugar cane yield was achieved in case of using irrigation gated pipe at L100 with 0.1 % slope treatment. On the other hand, the minimum value of sugar cane was achieved in case of irrigation traditional method at L 75 treatment. The average values of sugar cane yield were 55 and 42 ten/fedan under gated pipe and traditional irrigation method respectively. The irrigation with gated pipe improved yield WUE for sugarcane crop under three treatments furrows lengths compared to traditional irrigation.

Evaluation of Energy Dissipation Using Different Drop Broken‐Back Culverts Under Pressure Flow Conditions

Hydraulic jumps formed in broken‐back culverts were investigated experimentally by using energy dissipation devices. Additional examination measured the reduction in scour downstream of different‐height broken‐back culverts by forming a hydraulic jump inside the culverts. A broken‐back culvert model in the laboratory represents 150 ft in the field. The results were analyzed in terms of the inlet Froude number and different drop heights of broken‐back culverts. The calculated efficiency of energy dissipation in the culverts ranged between 55 and 90%. The dimensionless charts were created on the basis of data collection showing the relationship between the different relative drops and optimal sill height, optimal sill location, total head losses, optimal end sill, Froude number, and efficiency of hydraulic jump. The objective of this research was to obtain the maximum energy dissipation in different drop heights using analysis of dimensionless relationship charts.

Review: Hydraulics of water wells—head losses of individual components

Knowledge about the hydraulics of water wells is important to optimize their energy efficiency. By minimizing head losses around the well, energy consumption and ageing processes can be limited, thereby prolonging the well’s service life. The contribution of the individual components to total head loss (drawdown) in the well is analyzed in detail. The single most important contributor to drawdown is commonly the aquifer. Its hydraulic conductivity can only be improved slightly through development. The second most important contributor is the formation of a wellbore skin layer. This occurs if no proper well development was performed after drilling; the layer contains remnants of drilling-fluid additives or mobilized fine aquifer particles. The head loss caused by groundwater flow in the gravel pack, through the screen slots and inside the well, was found to be small. Thus, well development is the most important measure to influence well performance and energy efficiency. For longer operation times and pumped volumes, the energy gains outperform the cost for the development.

Influence Experiment for the Spacing Distance of Orifice Plates to Local Resistance Coefficient in the Pressure Delivery Pipeline

In order to research the influence rule of the spacing distance between orifice plates to the local resistance coefficient and total local water head losses , carried out the experiment research through set the two different relative distance of orifice plates in the pressure delivery pipeline. The experimental results showed that: When the relative distance, the results of total local water head losses calculated by the traditional hydraulics formula with the real measured data, the maximal relative error was less than 3%. This shown that when the relative distance was big, it was no necessary to consider the influence of the relative distance between orifice plates. However, when the relative distance, the real measured data of the total local water losses was much smaller than the calculated data by the traditional calculation formula, the maximal relative error was reached 239.5%. It was explained that when the relative distance was relative small, existed the adjoining influence between orifice plates, so the total local water losses by the multi-orifice plates was not equal to the sum of each water head loss by the single orifice plate, and the total local head loss was not necessarily increased with the number of orifice plates increasing. Whether or not the increasing total local water head losses was closely related with the relative distance of the orifice plates. The traditional local water head loss calculation formula in the hydraulics should be corrected and modified.

THE EFFECT OF PLUGGING STORM PIPE CULVERT ON HEAD (I)

Plugging storm pipe culvert changes the flow phenomena causing increasing the total head losses which sometimes make the flow to flood over and above the road. The experimental study in this research aims to discuss the effect of the plugging ratio on the total energy head loss. A plugging ratio,Ar = 50% of the pipe cross section, and a longitudinal plugging length, Lr= 0%, i.e. no plugging as a reference, 25%, 50%, 75%, and 100%. The pipe culvert was tested for five different discharges (Q=8.50 to 38.84 lit. /sec) and three submergence ratios (Y2/d = 1.0, 1.5, and 2.0). Dimensional analysis was employed to get the relationships between the different variables affecting the head loss through the plugging culvert. The results of the study led to practical recommendations that may be useful for decision makers to determine the suitable time for maintenance in order to decrease the total energy head losses and reduce road failure.The reduction percentage of the pipe efficiency decreased about 5% at Lr= 25% for Y2/d=1.0 and by 14% at Lr= 100% for average pipe Froude number Fp = 0.46 at Y2/d = 2.0.

Statistical Modeling of Head Loss through Duct Fittings in Conditioned Air Distribution Systems

Fractions of the total head loss which constitute the loss through duct fittings, obtained in an earlier study, for varying numbers of supply outlets and lengths of index duct run were used in a regression analysis to obtain second order equations which gave a general increase of the fraction from 0.598 to 0.713 for an increase in number of outlets from 3 to 19 and for a corresponding increase of 11.2 m to 43.2 m in index duct length. The correlation coefficient between the fraction of loss through duct fittings and each of the variables of number of supply outlets and length of index duct run was 0.823, which was found to be acceptable for a 95% confidence level. The ratios are useful for quick estimate of total pressure losses in conditioned air distribution systems which are needed in determining the fan pressure requirements.

Minimizing the Head Losses Increases Caused by Valves in Hydraulic Networks

This paper presents a hybrid model that calculates the heads, the discharges in pipes, the head losses in pipes (caused by discharges and valves) and the booster heads in hydraulic networks. The steady state is calculated considering the hydraulic network without valves and boosters. The extended period simulation is calculated considering the presence of valves and/or boosters to solve over pressure and/or under pressure problems respectively. The hybrid model uses a genetic algorithm to minimize the dissipated hydraulic power sum in the whole hydraulic network for all calculation time steps of the extended period simulation (objective function) by setting optimal valve openings. It was studied how it affects the behavior of a hydraulic network. A real hydraulic network that had over pressure and under pressure problems was analyzed. It was necessary to install boosters and valves to solve the pressure problems. The results show that when valves were installed without planning its openings, the total head losses increased from 5.9% to 13.6%, while the total head losses in the same hydraulic network increased 2.7% when planning the installed valves openings. It’s concluded that the dissipated power minimization was an effective way to optimize the studied hydraulic network operations by minimizing the head losses increases caused by the installed valves.

Optimum Design of Penstock for Hydro Projects

Penstock, a closed conduit, is an important component of hydropower projects. Various methods are available for optimum design of penstock. These methods are either based on empirical relations or derived analytically by optimizing the friction loss in the penstock. These formulae produce different values of penstock diameter for same site. In this study, formulae available for penstock design have been compared to review their suitability. A new method has been developed for the optimum design of penstock based on minimizing the total head loss comprising of friction and other losses. By using new developed method, diameter and annual cost of penstocks for few Hydro Electric plants of varying capacity have been worked out and reduction in annual cost of penstocks have been found in comparison to penstock cost for these projects.

Computer-Based Analysis of Hydraulic Design Variables for Uniformly Sloping Microirrigation System Laterals

AbstractAdequate analysis of lateral hydraulics is a very important concern for the design and evaluation of microirrigation systems. One of the main tasks of the lateral hydraulic calculation is to determine the pipe geometric characteristics (pipe size and length) with the required operating inlet pressure head, and the total friction head losses along the lateral line, assuming that the total flow rate at the inlet, characteristics of the emitter, and the acceptable level of uniformity are known in advance. This paper aims to present an efficient computer program in Visual Basic 6.0, named “Multi-flowCAD,” which is based on a stepwise computation algorithm for determining the hydraulic design variables (pipe size, pipe length, and operating inlet pressure head) and the hydraulic flow characteristics (emitter outflow-pressure head distribution, lateral discharge, and total friction losses) along the energy-grade line. The stepwise algorithm takes into account the velocity head change and variation of th...

The effect of low‐permeability fault zones on groundwater flow in a compartmentalized system. Experimental evidence from a carbonate aquifer (Southern Italy)

AbstractThe hydrogeological behaviour of fault zones in carbonate aquifers is often neglected in conceptual and numerical models. Furthermore, no information is available regarding the relationships between piezometric levels when significant compartmentalization occurs due to the occurrence of low‐flow fault zones. The aim of this study was to refine the conceptualization of subsurface flow in faulted carbonate aquifers and to analyse relationships between sub‐basins within a compartmentalized aquifer system in Southern Italy. The interactions between compartments that straddle low‐flow faults were investigated over four hydrologic years using a statistical approach to compare (i) the hydraulic heads within two wells located up‐ and down‐gradient of tectonic discontinuities as well as (ii) the rainfall and piezometric levels.The results of this study suggest that a set of barriers exists between the wells, and, therefore, the total head loss observed between the wells (approximately 80 m) should be distributed across several aquitards, with one aquitard exhibiting a relatively high permeability or low degree of integrity. Due to slight differences in permeability, transient conditions in aquitards can occur over relatively short periods, which is in agreement with the results of the statistical data analysis. Consequently, rather than being caused by pure aquitards, aquifer system compartmentalization likely results from slight differences in the permeability between lower‐permeability fault zones and adjacent higher‐permeability protoliths. Copyright © 2014 John Wiley & Sons, Ltd.

Artificial neural network based equation to estimate head loss along drip irrigation laterals

This work proposes an equation based on Artificial Neural Network (ANN) to estimate head loss along emitting pipes accounting for cylindrical in-line emitters. The following input variables were used to fit the model: total head loss between two consecutive emitters; emitter spacing; internal diameter of the pipe; mean water velocity at uniform pipe sections; and, kinematic viscosity of water. The input data was obtained by experimental means and standardized from 0 to 1. Five replications and six distinct structures of ANNs multilayer perceptron (MLP) were used during the training stage performed using the package neuralnet of the software R. A MLP structure consisting of six neurons at input layer, six neurons at hidden layer, and one neuron at output layer was applied for fitting the model. Estimated values by the ANN’s equation were compared to the estimated values by an equation based on dimensional analysis. The ANN’s equation and the equation based on dimensional analysis presented maximum deviations between measured and estimated values of 0.324 kPa and 1.647 kPa, respectively. Therefore the ANN’s equation presented better results than the equation based on dimensional analysis.

Determination of head change coefficients for dividing and combining junctions: A method based on the second law of thermodynamics

Losses due to the flow through conduit components in a pipe system can be accounted for by head loss coefficients K. They correspond to the dissipation in the flow field or, in a more general sense, to the entropy generation due to the conduit component under consideration. When only one single mass flow rate is involved, an entropy based approach is straight forward since the flow rate can be used as a general reference quantity. If, however, one mass flow rate is split or two partial flow rates come together like in junctions, a new aspect appears: there is an energy transfer between the single branches that has to be accounted for. It turns out that this energy transfer changes the total head in each flow branch in addition to the loss of total head due to entropy generation. Therefore, appropriate coefficients for junctions should be named as head change coefficients. As an example, the method is applied to laminar flows. Head change coefficients for dividing and combining flows in a T-shape micro-junction are determined for both branches and discussed with respect to their physical meaning. For the combining junction, the special case of engulfment, leading to enhanced mixing in micro-mixers, is also considered. Finally, it is shown, how the newly defined coefficients can be used for the design of a flow network.

Numerical modelling of bridges in 2D shallow water flow simulations

SUMMARYTwo representations of bridges are presented to fit into simulations based on the 2D SWEs. They include a novel and simple empirical formulation for total head loss caused by bridges which covers all flow regimes: free water surface, partially submerged flow, and fully submerged flow. The performances of the different representations of bridges are assessed using experimental results of steady and unsteady flows, presented for the first time in this work. A case study of a real flood is presented giving insight into the application of the representation techniques to real engineering problems. The proposed solution of a head loss representation together with the novel formulation is shown to be accurate for both steady and unsteady flows, and to perform efficiently for solving the flood case. Copyright © 2014 John Wiley & Sons, Ltd.

Features on Head Loss of Flocculation Tank Installed with Small Mesh Grid

Small mesh grid is mostly used as flocculation equipment in present water plant, and its head loss is closely related to flocculation effect. Flocculation tank installed with several grid groups in different mesh sizes were tested with a view to evaluating its head loss characteristics, including the frictional and local head losses. The tests were carried out at pilot scale, using a steel tank as flocculation basin. The grids are made of plastic material and the cross section size of the grid trips is 7 mm in width and 2 mm in height. The results indicate that relative roughness is most associated with frictional resistance coefficient (FRC), whereas Reynolds number was unrelated to that. The ratio of frictional head loss to total head loss of the basin does not vary with the variation of channel velocity, and the ratio is always less than 6% in this case. Local resistance coefficient (LRC) decreases with the increase of mesh size. In order to improve the utilization rate of head loss, the preferred mesh size of the grid should be 30-40 mm. The optimal space between the neighboring grid layers can maximize the utilization of turbulent kinetic energy loss generated by grids.

Simultaneous topology and sizing optimization of a water distribution network using a hybrid multiobjective evolutionary algorithm

This paper proposes a new direction for design optimization of a water distribution network (WDN). The new approach introduces an optimization process to the conceptual design stage of a WDN. The use of multiobjective evolutionary algorithms (MOEAs) for simultaneous topology and sizing design of piping networks is presented. The design problem includes both topological and sizing design variables while the objective functions are network cost and total head loss in pipes. The numerical technique, called a network repairing technique (NRT), is proposed to overcome difficulties in operating MOEAs for network topological design. The problem is then solved by using a number of established and newly developed MOEAs. Also, two new MOEAs namely multiobjective real code population-based incremental learning (RPBIL) and a hybrid algorithm of RPBIL with differential evolution (termed RPBIL–DE) are proposed to tackle the design problems. The optimum results obtained are illustrated and compared. It is shown that the proposed network repairing technique is an efficient and effective tool for topological design of WDNs. Based on the hypervolume indicator, the proposed RPBIL–DE is among the best MOEA performers.

Economic optimization method to design telescope irrigation of multiples outlets

In this study is presented an economic optimization method to design telescope irrigation laterals (multidiameter) with regular spaced outlets. The proposed analytical hydraulic solution was validated by means of a pipeline composed of three different diameters. The minimum acquisition cost of the telescope pipeline was determined by an ideal arrangement of lengths and respective diameters for each one of the three segments. The mathematical optimization method based on the Lagrange multipliers provides a strategy for finding the maximum or minimum of a function subject to certain constraints. In this case, the objective function describes the acquisition cost of pipes, and the constraints are determined from hydraulic parameters as length of irrigation laterals and total head loss permitted. The developed analytical solution provides the ideal combination of each pipe segment length and respective diameter, resulting in a decreased of the acquisition cost.

홍수터여과에서 집수관의 최적설계 연구

In order to obtain information on the design parameters of the horizontal laterals in floodplain filtration, laboratoryscale sand-box experiments were performed where the head distributions on the laterals and the groundwater profiles were measured according to the change in parameters including lateral diameter, hydraulic conductivity of the sand, water level at the well and raw-water supply rate. Measured data were analyzed using a numerical code in order to identify the discharge intensity distribution along the laterals. It was observed from the result that the lowering of the water level at the well had minimal adverse effect on the performance of the floodplain filtration. Results also elucidated that the low conveyance of the laterals to transmit the filtrate was compensated and supplemented by a natural augmentation in horizontal conveyance through the aquifer when the raw-water supply rate exceeded the adequate recovery rate. With this mechanism, the water quality is expected to improve further since the travel distance through the aquifer is amplified. Based on these findings it can be suggested that the diameter of the lateral used in the floodplain filtration may be smaller than those in riverbank/bed filtration. It was also found that the ratio between the head loss occurring in a lateral and the total head loss in the floodplain filtration was proportional to the exit velocities of the laterals, which may be used to design and/or evaluate the lateral in floodplain filtration.