Upstream Head Research Articles

Effect of weep hole and cut-off wall on hydraulic gradient and uplift pressure under a diversion dam

In hydraulic structures such as diversion or gravity dams constructed on a porous foundation, the difference in water levels between upstream and downstream results in water seepage through the porous soil under the dam. This seepage flow generates uplift pressure under the structure that may cause a crack on the concrete surface of the structure’s floor. In this condition, the exit gradient may exceed the critical value and cause the piping phenomenon. In this study, the effect of the weep hole and cut-off wall on the uplift pressure and the hydraulic gradient under a diversion dam was investigated experimentally and numerically. For this purpose, four weep holes (diameter = 1 cm) were embedded along the longitudinal axis of the stilling basin. The weep holes were examined in single and combined modes. The experiments were conducted in three upstream water heads of 10, 15, and 20 cm. The results showed that in terms of seepage losses, hydraulic gradient, and uplift pressure, the binary combinations of weep holes are better than the other modes. Among the binary combinations, the combination of the two closest weep holes to the dam toe (weep holes 1 and 2) had the most proper performance. In the supplementary experiments, a cut-off wall in two depths (10 and 15 cm) was placed at the dam heel in addition to the best modes of weep holes combination. Overall, the simultaneous use of cut-off wall (especially 15 cm) and weep holes improved the hydraulic condition of seepage phenomenon under the dam.

Experimental study and artificial intelligence-based modeling of discharge coefficient of converging ogee spillways

ABSTRACT Converging ogee spillway is employed as an emergency spillway constructed to control natural disasters such as instant floods. This paper presents an experimental study and artificial intelligence-based modeling of the discharge coefficient (Cd ) of the converging ogee spillway (with a curve axis). The ogee spillway structure was tested in both symmetrical and asymmetrical convergence of training walls ranging from 0° to 120°. Through the visual observation, it was found that the tailwater submergence, the depth of approach, the crest and spillway geometry, the head different from design head, and downstream floor position are the important factors that alter the Cd of the converging ogee spillway. Moreover, two different methods (e.g. gene expression programming (GEP) and adaptive neuro fuzzy inference systems (ANFIS)) were assessed for modeling the Cd using original experimental data. Based on the obtained results, both the GEP and ANFIS models have reliable performance in simulating the Cd . Moreover, the performance of GEP model was found to be slightly better than the ANFIS technique. According to the outcome of sensitivity analysis, the ratio of the total upstream head on the spillway to design head (H/Hd ) is the most important parameter for the optimum modeling of the Cd of the converging ogee spillway.

Short-term hydro scheduling of a variable speed pumped storage hydropower plant considering head loss in a shared penstock

In this paper we present in detail how to handle the nonlinear and state-dependent elements in the power consumption function (PCF) of a variable speed pump (VP). The function is formulated by piecewise linear approximations with dynamically specified breakpoints. In the proposed method, the head variation resulting from the change in the water level of the upstream and downstream reservoirs and head loss caused by the friction of water on the penstock wall are both considered. Furthermore, we put forward a heuristic to incorporate the head loss in a penstock shared by multiple VPs in a short-term hydro scheduling tool used for daily operation in the real world. The case study is taken from the Limmern pumped storage hydropower plant with 4×250 MW reversible Francis pump-turbines with variable speed technology. Each penstock is shared by two of the four units. The numerical results demonstrate that the appropriate formulation of the PCF and the accurate representation of the head loss in a shared penstock are crucial for obtaining realistic and optimal scheduling for VPs.

Influential parameters on submerged discharge capacity of converging ogee spillways based on experimental study and machine learning-based modeling

AbstractOgee spillways with converging training walls are applied to lower the hazard of accidental flooding in locations with limited construction operations due to their unique structure. Hence, this type of structure is proposed as an emergency spillway. The present study aimed at experimental and machine learning-based modeling of the submerged discharge capacity of the converging ogee spillway. Two experimental models of Germi-Chay dam spillway were utilized: one model having a curve axis which was made in 1:50 scale and the other with a straight axis in 1:75 scale. Using visual observation, it was found that the total upstream head, the submergence degree, the ogee-crest geometries and the convergence angle of training walls are the crucial factors which alter the submerged discharge capacity of the converging ogee spillway. Furthermore, two machine-learning techniques (e.g. artificial neural networks and gene expression programming) were applied for modeling the submerged discharge capacity applying experimental data. These models were compared with four well-known traditional relationships with respect to their basic theoretical concept. The obtained results indicated that the length ratio () had the most effective role in estimating the submerged discharge capacity.

Simple flowmeter device for LID systems: From laboratory procedure to full-scale implementation

Low impact development (LID) systems provide sustainable solutions for flood risk mitigation. Given their relevant role in urban water management, accurate estimation of the outflow rate of such systems is crucial to assess their retention efficiency and the corresponding volumes discharged into the drainage network. Thus, the selection of an appropriate flowmeter device is necessary. Thus far, various flowmeter devices have been designed and calibrated for pipes, open channels, rivers, and irrigation systems, while only scarce and general information has been presented for the devices used in LID systems. The main objective of this study is to propose a new, simple, and easily replicable flowmeter device, which can be positioned in confined spaces, such as drain wells, for measuring a large outflow rate range of LID systems. To identify the most influential parameters on the discharge coefficient, the evolutionary polynomial regression multi-objective and multi-case strategy approaches were used for data mining. The results demonstrate that the ratio between the upstream head (h) on the weir crest and the weir width (b), namely the (h/d) parameter, significantly affects the discharge coefficient. Therefore, neglecting the Reynolds and Weber condition and h/d coefficient (where d is the weir height), a simple and accurate relationship of the discharge coefficient was obtained. Finally, to implement the laboratory findings to a full-scale green roof, the runoff collected by the developed device for a continuous period of three months was analysed. The findings demonstrate that the plotted hydrographs do not exhibit fluctuations and effectively interpret the small flow, at both the continuous and event scales.

Energy, cost and uniformity in the design of drip irrigation systems

A novel approach for the design of drip irrigation systems is presented. The diameters of the laterals and submains were calculated by minimising an objective cost function that includes investment and operating costs of drip irrigation units. Diameters, head loss and its distribution between laterals and submain, average operating pressure head, upstream end energy head and the distribution uniformity were all deduced from an economic approach. These variables are not matched alone but are the consequence of the economic optimisation. Several examples with self-compensating and non-compensating emitters fed from either a pump station or a water reservoir are presented to illustrate the feasibility of the proposed methodology.

Effects of initial stage of dam-break flows on sediment transport

Experimental and numerical studies of dam-break flows over sediment bed under dry and wet downstream conditions are investigated and their effects on sediment transport and bed change on flow are illustrated. Dam-break waves are generated by suddenly lifting a gate inside the flume for three different upstream reservoir heads. The flow characteristics are detected by employing simple and economical measuring technique. The numerical model solves the two-dimensional Reynolds-Averaged Navier–Stokes (RANS) equations with k-ε turbulence closure using the explicit finite volume method on adaptive, non-staggered grid. The model is validated with laboratory data and is extended for simulating non-equilibrium sediment transport and bed evolution process. The volume of fluid technique is used to track the evolution of the free surface, satisfying the advection equation. The comparison study reveals that the current model is capable of defining the dam-break flow and improves the accuracy of determining morphological changes at the initial stages of the dam-break flow. A good agreement between the model solutions and the experimental data is observed.

Effect of Sediment Concentration on Hydraulic Characteristics of Energy Dissipation in a Falling Turbulent Jet

The effect of sediment on the hydraulics of jet energy dissipation is an urgent issue for high dams built on sediment-laden rivers. Accordingly, flume experiments were conducted using a ski-jump type energy dissipator in flows of four sediment concentrations (0 kg/m3, 50 kg/m3, 150 kg/m3, and 250 kg/m3) to determine the effects on discharge, flow regime, and hydrodynamic pressure in a plunge pool. The results demonstrate that the effect of sediment on discharge is constant, regardless of sediment concentration, when compared to fresh water. The width of the nappe decreased with increasing concentrations of sediment. The length of the jet trajectory increased with upstream water head. The time-averaged pressure and fluctuation pressure both exhibited peaks, describing the impact of the jet on the bottom of the plunge pool. The maximum time-averaged pressure and maximum fluctuating pressure both noticeably increased with upstream water head and slightly increased with sediment concentration for a given flow condition. The results also demonstrated that the dominant frequency of fluctuation trends to lower values, and that both the fluctuating energy and vortex scale increase with increasing sediment concentrations due to increased viscosity. These findings can be used to improve energy dissipation in dams on sediment-laden rivers.

Impacts of multi-gate regulator operation schemes on local scour downstream

ABSTRACT Regulators are commonly used to control and measure flows in streams and irrigation canals. Inadequate operation of regulator gates may lead to scour downstream, possibly leading to structural failure. An experimental work was conducted to study the effect of different regulator gate operation schemes on scour hole formation downstream under free-flow conditions. The experimental model consisted of five sluice gates, a solid apron, and a mobile bed (sand). One hundred and thirty-five different gate operation schemes were studied by changing the number of opened gates and the gate arrangement with different hydraulic conditions. The parameters considered in this study were the downstream Froude number, tail water depth, upstream water head, and the number of opened gates and their arrangements. A dimensional analysis was applied to obtain non-dimensional quantities that describe the different variables affecting scour downstream the gates. The obtained results of the experimental tests were analysed and graphically represented. It was observed that the number of opened gates and their arrangements had significant effects on the scour hole pattern under different hydraulic conditions. The most favourable operation case was with all five open gates opened, while the least favourable operation case was with only the side gate opened.

Pollutant fate and spatio-temporal variation and degree of sedimentation of industrial- and municipal wastes in Chakbandi drain and River Chenab.

This study’s objective was to assess a seasonal impact of industrial and sewage waste disposal on water quality of the river upstream Trimu Head. Considering the significance of the river, drain wastewater was analyzed during the summer and the winter seasons from pre-determined locations. Water quality parameters were recorded higher than the maximum permissible limits prescribed by WHO for freshwater bodies. Level of these Physio-chemical variables was higher in the winter due to the least amount of water from domestic sewage. Although some of these parameters indicated sedimentation hitherto the water quality of River Chenab was found very poor due to the pollution bestowed by tributary waste water from drains. Findings of this investigation suggest the importance of continuous monitoring and assessment to improve the water quality of the river. This study provides a baseline data which may be compared to assess any further deterioration in the water quality and may also be used to plan future monitoring and required restoration of habitat for the safe supply of fish to the population of this region.

Validation of a numerical particle based method for free surface flow downstream of sluice gates

This study is a numerical investigation in which a meshfree computational method known as the Smoothed Particle Hydrodynamics (SPH) is applied to examine its efficiency and accuracy in predicting the flow field variables of free surface flow passing a sluice gate. For this purpose, the numerical 2D SPHysics model, as an implementation of the computational SPH method, is adopted. The numerical code is validated against the theoretical and experimental results of previous works. The validation is performed taking into consideration the conjugate flow depths and velocities for different total upstream heads passing under a fixed gate opening height. The quantitative agreement between the results computed by the numerical 2D SPHysics code and the theoretical and experimental results is fairly good confirming that the numerical code is robust in predicting the flow properties in sluice gates. Then, the validated code is used to find the energy dissipation rate for various total upstream heads and Froude numbers. The results obtained in this study are promising, indicating that the numerical model can be considered as an efficient alternative tool for hydraulic engineers to predict and understand the flow behavior in hydraulic structures.

Numerical study of characteristics and discharge capacity of piano key weirs

A comprehensive numerical investigation was performed to better understand the flow patterns of Piano Key weirs (PKW) for different upstream heads, based on the volume-of-fluid model. The results of numerical simulation indicate that, the efficiency of side crests are limited by following factors: the change of side crest flow direction caused by the effect of the longitudinal flow velocity along the inlet keys, submerged flow regime in outlet keys, interference between nappes, and the head loss along the inlet keys, under the conditions of high upstream head, which eventually leads to the decrease in discharge efficiency with an increase in the upstream head. An orthogonal analysis revealed that, the weir height, inlet/outlet key width ratio, significantly affect the piano key weir discharge efficiency. New formulas with obvious physical significance and high accuracy for the piano key weir discharge were then derived and verified, which improve the accuracy of the design and structural optimization of the piano key weir.

Abstract 19: Establishment of an upstream head and neck precision oncology tumor board

Abstract Background: Precision medicine is rapidly becoming incorporated into the management of head and neck cancers. Institutional precision tumor boards are emerging, mostly in frameworks that are not specific to head and neck cancers, and are focused on recurrent and metastatic (R/M) disease. There are significant benefits to a subspecialized focus on head and neck cancers without restricting enrollment to R/M cases. Herein, we discuss the establishment of a unique, upstream head and neck precision oncology program. Methods: We have established a head and neck precision oncology model that is run by head and neck surgeons and translational scientists, in combination with colleagues from radiation oncology, medical oncology, genetics, and ethics. Inclusion criteria stipulate adult patients with biopsy-proven malignancy of the head and neck (newly diagnosed or previously treated, including all sites, stages and histologies) who have pathologic samples available for analysis (fresh frozen or paraffin embedded). Results: We have begun enrolling patients prospectively (n=47 to date; 39 primary tumors and 8 R/M tumors). A custom Illumina 250 gene sequencing panel is utilized for targeted sequencing compared to matched blood. At the time of subject enrollment, we have incorporated a novel informed consent process involving ethicists and genetics counselors, with prospective collection to validate our informed consent process, discussion of disclosure of incidental findings, and clarifying patient expectations. Sequencing data are then presented formally at our head and neck precision oncology tumor board. Discussion: A primary benefit of a head and neck precision oncology tumor board is the integration of multidisciplinary expertise both from a clinical and cancer biology perspective. Our model of counseling, in which we employ a flexible default model of information disclosure, provides unique and valuable prospective information on patient expectations and understanding in disclosure of genetic results, clinical translation, and enrollment in targeted therapy trials. Unique to this model is a focus on enrolling patients up-front, at their initial presentation to our institution. This platform allows for early identification of potential targetable genetic aberrations (in adjuvant and neoadjuvant settings), and allows for evaluation of tumor genomic evolution/mutational selection if the patient develops R/M disease (which may allow for more specific targeted therapy to the mutation that appears to be driving the aggressive tumor biology). Citation Format: Andrew Birkeland, Aditi Kulkarni, Collin Brummel, Susan Foltin, Mark Prince, Carol Bradford, Andrew Shuman, J. Chad Brenner. Establishment of an upstream head and neck precision oncology tumor board [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; April 23-25, 2017; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(23_Suppl):Abstract nr 19.

Flow Characteristics of Triangular Plan Form Weir

Weirs are used for discharge measurement and flow diversion in the open channels. However, modified weirs such as plan form weirs, Labyrinth weir, oblique weir and piano key weir, etc. having larger crest length compared to normal weir having same lateral space assist in enhancing discharging capacity for a given upstream head, without creating much afflux. An experimental study was carried out to understand the effect of the geometry of a triangular plan form weir on discharge coefficient under free and submerged flow conditions. In this paper attempts are made to investigate working of triangular plan form weir of vertex angle 45° with three heights 10, 20 and 30 cm under free and submerged flow conditions. The discharge coefficients were calculated under free & submerged flow conditions and the results were compared with normal weirs as well. Further, triangular plan form weir is quite simple device/geometry and easy to install & quite useful for discharge measurement in open channels.

Discharge coefficient of semi-circular labyrinth side weir in subcritical flow

Side weirs are flow diversion or intake devices that are widely used in irrigation and drainage networks and urban sewage systems. Labyrinth weirs have a proven hydraulic advantage due to their increased discharge rate at the same head for a given design condition. A labyrinth weir is defined as a weir crest that is not straight in plan-form. The increased sill length provided by labyrinth weirs effectively reduces upstream head to the particular discharge. In this study, a comprehensive laboratory study was conducted in a physical model of a semi-circular labyrinth side weir and the model is evaluated for three heights and three radii. In this particular study, the hydraulic effects of this shape of side weir in increasing discharge capacity was investigated. The discharge coefficient of semi-circular labyrinth side weirs was determined and the results were analysed to find the influence of the dimensionless parameters of weir height ( w/b ), weir length ( r/b ), nape height (( y 1 −w)/r ), and upstream Froude number ( Fr 1 ) on discharge coefficient ( Cd ), based on the experimental conditions and previous studies. It was found that the discharge coefficient of the semi-circular labyrinth side weir gives a relatively high discharge coefficient value compared to other types of classic side weir positioned on a straight channel. Additionally, reliable equations for calculating the discharge coefficient ( Cd ) of semi-circular labyrinth side weirs are proposed. According to the proposed equation, Cd depends on dimensionless parameters, which are the ratios of r/b, r/w , ( y 1 −w ) /r , ( y 2 −w )/ r and Fr 1 . Keywords: side-weir, discharge coefficient, semi-circular labyrinth side weir, subcritical flow

Experimental Investigation of the Dynamics of Laboratory Simple Surge Tank

The surge tank is one of important control devices inreducing water Hummer effect on distributed network pipingsystem and hydropower stations. An experimental study wasconducted into a simple surge tank of 0.044 m in a diameterwith upstream constant head reservoir of a height, 0.881 mand a water transporting pipe of a size 0.0202 m.Results indicate that rapid closure of a downstream valvecauses under-damped stable oscillation in a surge tank.Experimental response agreed well with theoretical resultswhen friction factor is considered to be variable, but with 85% increases in settle time and more oscillations when constantfriction factor is recognized at initial value before valveclosure. Doubling surge tank area does not improve thedynamics properties; otherwise, Thoma area must be avoidedfor small sizes. Comsol multiphysics software 3.5 is used todeal with the dynamics of the surge tank numerically.

Prediction of discharge coefficient of triangular labyrinth weirs using Adaptive Neuro Fuzzy Inference System

In this paper, the discharge coefficient of triangular labyrinth weir was predicted using multi-layer perceptron (MLP) neural network and Adaptive Neuro Fuzzy Inference System (ANFIS). To this purpose, 223 related dataset were collected. The Gamma Test (GT) was carried out to obtain the most affective parameters on the discharge coefficient. The results of the GT indicated that the ratio of length of crest of weir to the main channel width Lw/Wmc, the ratio of length of one cycle to its width (Lc/Wc) and the ratio of total upstream head flow to the weir height H/P are the most important parameters. With regarding to the results of the GT, the structure of ANFIS model was designed. The results of ANFIS model with error indices including coefficient of determination value of 0.97 and root mean square error value of 0.03 was so suitable. Comparison the results of MLP with ANFIS model showed that both models has so suitable performance however the structure of ANFIS model is more optimal.

Comparison the hydraulic characteristics of finite crest length weir with quarter-circular crested weir

Weirs are used for flow measurement, flow diversion and water level control in open channels. In this study, experiments were conducted on finite crest length weir and quarter-circular crested weir and hydraulic characteristics of two weirs were compared together. Depending on the ratio of total upstream head H to weir crest length L, flow over the finite crest length weir was undular, parallel to the crest surface or curvilinear. Also, for H/L>1.82, lower nappe separated from the upstream corner of crest and did not reattach to the crest surface. In the range of conducted tests (H/L<2.20), flow over the quarter-circular crested weir was curvilinear and lower nappe did not separate from the crest surface. Due to the elimination of separation zone, which is the primary source of energy loss, discharge coefficient for quarter-circular crested weir is significantly larger than for finite crest length weir. Furthermore, negative (sub-atmospheric) pressure on the crest surface of finite crest length weir and quarter-circular crested weir occurred for H/L>1.52 and H/L>2.2, respectively. This result indicates that quarter-circular crested weir is less sensitive to cavitation danger.

Multi- Objective Optimal Design of on- Demand Pressurized Irrigation Networks

In the context of water as an economic good, from the use of water, one can derive a value, which can be affected by the reliability of supply. On-demand irrigation systems provide valuable water to skilled farmers who have the capacity to maximize economic value of water. In this study, simultaneous optimization of on-demand irrigation network layout and pipe sizes is considered taking into account both investment and annual energy costs. The optimization problem is formulated as a problem of searching for the upstream head value, which minimizes the total cost (investment and energy costs) of the system. The investment and annual energy costs are obtained in two separate phases. Max–Min ant system (MMAS) algorithm is used to obtain the minimum cost design considering layout and pipe diameters of the network simultaneously. Clement methodology is used to determine flow rates of pipelines at the peak period of irrigation requirements. The applicability of the proposed method is showed by re-designing a real world example from literature.

Scale effects in physical piano key weirs models

ABSTRACTWith inertia and gravity representing the dominant forces for most open channel flow applications (e.g. weir flow), Froude similitude is commonly used for scaling hydraulic performance data from the model to prototype structures. With weir flow, as the upstream head decreases, however, the relevance of surface tension and viscosity forces can increase to the point when the model and prototype similitude is not fully achieved through Froude scaling. Such discrepancies are referred as size-scale effects, and among other things, can result in variations in the head–discharge relationship, nappe trajectory, and air entrainment. Published criteria for avoiding significant size-scale effects for free flow over linear weirs have suggested that minimal heads of ∼0.02 to 0.07 m be respected, independently of the model size. In this study, the size-scale effect, minimum upstream head, and Weber number limits are investigated for four piano key weirs with geometric model scales of 1:1, 1:7, 1:15, and 1:25.