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Experimental survey of energy dissipation in nappe flow regime in stepped spillway equipped with inclined steps and sill

Experimental survey of energy dissipation in nappe flow regime in stepped spillway equipped with inclined steps and sill

At the institute of water research, recent research has been done on the 1:15 scale modeled stepped spillway. Material of steps and walls of stepped spillway are plexiglass and has been mounted on metal frame. Wall thickness is 10 mm. Used a wide-brimmed shot spillway and the numb er of shot steps is 60, among these 4 steps have been change d shortly after the middle of the spillway. Step length is 14 cm, the step height is 4.66 cm, width of spillway is 1.33 m and height from spillway crest to the bottom of the first step is 5 cm. The measured parameters in research included flow depth, speed, static pressure on the bottom of the steps and pressure fluctuations. Water’s depth is measured by Point gauge, velocity by Pitot tube and static pressure is measured by pi ezometers. Also a transducer was used to register the pressurre fluctuations, so that for every piezometer, 200 data is recordded per second for 30 seconds. To measure the water surface le vel in the tank, bar measurement is used and flow rate is meas ured with the help of a sharp- edged rectangular spillway at the end of downstream channel of the shot. Of course, to ensure the accuracy of flow rate, compared it with the flow over the spillway that has been calculated. Pegram et al. experimented stepped spillways on the scale of 1:10 and 1:20 and concluded that models with a scale of 1:20 or greater can present a real spillway behavior by the similarity of Fr oude number [5]. According to this, recent study results, can be used for spillway 15 to 20 times larger. The shape and slope characteristics of sills which have been us ed are as follows: Three dip includes 7, 10 and 12 degrees were used.

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Evaluation of Computational Fluid Dynamic Model in Investigating the
Hydraulic Performance of Stepped Spillway

Evaluation of Computational Fluid Dynamic Model in Investigating the Hydraulic Performance of Stepped Spillway

In recent years, new hazard classification for existing reservoirs have been changed because boundary conditions have been developed. Consequently, many of these dams no longer provide adequate spillway capacity according to state and federal dam safety regulations. Stepped spillways are a most powerfully choice for provide a means to increase flowrate capacity without necessarily causing other modifications to the dam dimensions. The stepped spillway, one of the most important types of spillway used to reduce the size and depth of the energy dissipation tank at the toe of the dam. This type of spillway works to dissipate the energy through the movement of water over the aging of the steppes, resulting in water vortices during the transition from the upstream of the spillway to downstream.

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Flow Characteristics and Energy Dissipation Losses in Different Configurations of Steps of Stepped Spillway

Flow Characteristics and Energy Dissipation Losses in Different Configurations of Steps of Stepped Spillway

Abstract:This study based on laboratory experiments aims to investigate the flow characteristics and energy dissipation rates on six different configurations of steps of stepped spillway which are: (Inclined and endsills which were fixed on the downstream of the horizontal face of all steps, alternative endsills and horizontal steps, steps combined with endsills and inclined started with endsills and steps combined with endsills and inclined but started with inclined), at physical model with ratio height to length of step (h/l= 0.8391) and (h=3cm) at skimming flow regime. Flow discharge variations were applied in each configuration and the hydraulic changes were investigated and energy dissipation rates were calculated and compared with conventional type of step of stepped spillway. The results showed that the using of different types of steps have the most influence on the amount of energy losses, they are increased the energy losses by about (1.6%-18.6%) at different runs and configurations in comparison of horizontal steps. The results indicated also that the energy dissipation rate at configuration of alternative inclined and horizontal steps show increased by about (6.2% at q=0.02119 m 3 /s/m) more than the configuration of alternative endsills and horizontal steps and by about (5.3% at q=0.02119 m 3 /s/m) more than configurations of inclined on all steps. Furthermore, use of compound horizontal and inclined steps alternatively has better performance in dissipating the flow energy in comparison with the horizontal steps, it is increased in the energy dissipation rate up to about (18.6 %) at (q=0.02119 m 3 /s/m).

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Air Entrainment and Pressure Fields over Stepped Spillway in Skimming Flow Regime

Air Entrainment and Pressure Fields over Stepped Spillway in Skimming Flow Regime

In case of stepped spillways the flow is highly turbulent and there is an every possibility of development of neg- ative pressure on some of the steps which lead to cavitations. Therefore, it is necessary to measure pressure on each step of the stepped spillway. In this model study, the peizometric tubes are fixed on step numbers 5, 7, 9, 14, 19, 24, 29 and 32 and pressure was measured on the centre of horizontal face of steps.

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Flow Characteristics and Energy Dissipation Over Traditional and Stepped Spillway with Semicircular Crest

Flow Characteristics and Energy Dissipation Over Traditional and Stepped Spillway with Semicircular Crest

In recent years, various investigators study the characteristics of flow over spillway. Stepped spillways have regained popularity over the last two decades, thanks to financial benefits resulting mainly from the simple economic and rapid construction procedure especially with the Roller Compacted Concrete (RCC) construction method [4]. Stepped spillways allow continuously dissipating a considerable amount of the flow kinetic energy, such that the downstream stilling basin, where the residual energy is dissipated by hydraulic jump, can be largely reduced in dimensions. Also, the cavitation risk along the spillway decreases significantly due to smaller flow velocities and the large air entertainment rate [5]. Chamani and Rajaratnam [6] show that, in a stepped spillway, jet flow would occur at relatively smaller discharges and skimming flow occurs at larger discharges. It also appears that for a wide range of slopes, the transition from the (lower) jet flow to the (higher) skimming flow occurs when y c /h is

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SPHysics Simulation of Experimental Spillway Hydraulics

SPHysics Simulation of Experimental Spillway Hydraulics

This study demonstrates the great potentials of the SPH modeling technique in practical engineering applications of a stepped spillway flow. By using the open source code parallelSPHysics to a documented benchmark and a self-implemented laboratory spillway flow based on the prototype hydraulic dam project, the numerical accuracy of the model is fully evidenced. The proposed push- paddle inflow model can generate a quite quite stable inflow hydrograph, which is also easy to program into the SPH numerical scheme and effective in reducing the computational domain by a large margin. The SPH computations are critically validated by the velocity and pressure data through either the literature or the laboratory measurement. An error analysis showed that the average errors between the numerical and experimental results are 0.8–4.3% in the horizontal pressures and 0.7–4.7% in the vertical pressures. Besides, the pressure distributions on the horizontal and vertical faces of the spillway step show significantly different patterns. On the former it is always positive with a peak value towards the outer edge of the step with a decreasing trend to the corner, while on the latter it has alternatively positive and negative pressure values, which is highest near the step corner and lowest near the step edge. In the study, three different step configurations are considered, i.e., the step numbered at 62, 45 and 31. The computed energy dissipations also agree with the experimental data within an error of 8.2%, 3.1% and 5.8%, respectively, for the above three step conditions. One highlight of the present study is that the SPH pressure computations on the step faces are quantitatively validated by the measured experimental data. It seems the parallelSPH could provide a promising simulation tool for the stepped spillway flows in a laboratory scale with great potentials in real hydraulic engineering.

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Experimentally determination of discharge coefficients of Ogee spillway under axial arc condition with convergent lateral walls

Experimentally determination of discharge coefficients of Ogee spillway under axial arc condition with convergent lateral walls

on the spillway. The results of this study provide users of numerical models performance information that can be used to aid them in determining which tool to use to effectively analyze dams and their associated spillways. Tullis and Neilson (2008) carried out the performance of submerged ogee spillway and proposed a relationship for discharge calculation. The results showed that for submergence levels <0.70, the head-discharge relationship was relatively independent of the tail water elevation, but at higher submergence levels, this was not the case. For submergence values <0.8, the submergence head-discharge data were best predicted using the free-flow head-discharge relationship. For submergence values <0.8, the accuracies of all but one of the head discharge relationships were very poor. For such high submergence levels, more accurate methods are needed for predicting submerged ogee-crest head-discharge relationships. Hunt et al. (2008) evaluated the convergence effects of the lateral walls in stepped spillway. Overall results indicated that flow behavior of the two sides of spillway is the same; transverse waves through the body of spillway were not observed; Furthermore, the water surface profiles showed that flow depth next to wall rapidly increased at the beginning of the convergent part. Khosrojerdi (1997), studied broad crest weirs in direct and curvature illustrations. He suggested that the axial arc, in addition to the structural stability toward the upstream, leads to the increase of discharge coefficient. Also, Khosrojerdi and Mehrjerdi (2007) stimulated the field of passing flow over ogee spillway using fluent software in three-dimensional condition. According to the results, discharge coefficient, static pressure and flow rate within the ogee section is more in the upstream curvature than downstream curvature and direct spillway.

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Unsteady Spillway Flows by Singular Integral Operators Method

Unsteady Spillway Flows by Singular Integral Operators Method

The Singular Integral Operators Method (S.I.O.M.) is applied to the determination of the free-surface profile of an un- steady flow over a spillway, which defines a classical hydraulics problem in open channel flow. Thus, with a known flow rate Q, then the velocities and the elevations are computed on the free surface of the spillway flow. For the nu- merical evaluation of the singular integral equations both constant and linear elements are used. An application is fi- nally given to the determination of the free-surface profile of a special spillway and comparing the numerical results with corresponding results by the Boundary Integral Equation Method (B.I.E.M.) and by using experiments.

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Execution Method for Spillway Hydraulic Surfaces: Upper Gotvand Dam

Execution Method for Spillway Hydraulic Surfaces: Upper Gotvand Dam

Varity of surface types available in Gotvand spillway structure specifically those with executive obstacles such as low width sections or surfaces with particular geometric conditions [3], make this method so beneficial. However insufficient progress speed because of the extent of hydraulic surfaces, necessity of employment of experienced skillful persons and strict technical tolerances available made us to speculate of other supplemental options. Thus appropriate bars were planned to resolve problem and facilitate concrete placement in different curved surfaces as well.

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Modeling the Mangla Dam Spillway for Cavitation and Aerators Optimization

Modeling the Mangla Dam Spillway for Cavitation and Aerators Optimization

The Mangla dam embankment is 380 ft (115.83 m) high above river bed and 10300 ft long (3140 m) long. It was proposed to raise the embankment height by 30 ft (9.14 m) and pool conservation level by 40 ft (12.20 m). The dam spillway is orifice type headworks, two-stage still- ing basin and sloping side walls. The headworks of the main spillway are 444 ft (135.33 m) long. It consists of three monoliths separated by 24 ft (7.3 m) wide piers. Each monolith comprised three orifices of 36 ft (10.97 m) width and 40 ft (12.2 m) height, which are equipped with radial gates. Each orifice within the monoliths is sepa- rated by 12 ft (3.66 m) wide pier. Parabolic chute follows the headworks crest. An intermediate weir divides the chute into two and creates a stilling basin and water pool at an elevation of 1000 ft (304.8 m). The spillway plan and the longitudinal sections are in Figure 1.

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1-Dimensional Hydraulic and Sediment Transport Modelling of an Emergency Spillway

1-Dimensional Hydraulic and Sediment Transport Modelling of an Emergency Spillway

Further to individual cross section presentation, the side profile plot can also be generated. Figure 37 shows the original channel invert elevation in black and the post event channel inert elevation in blue. The emergency spillway flow direction is from the right side of the diagram to the left. It can be observed that significant erosion occurs in the steep segment of the emergency spillway. This is expected as the steep slopes create high velocities and shear stress values, resulting in a higher potential for erosion. Around station 225 a significant dip can be observed. The channel cuts deep and then rises. This occurs where the pre-erosion channel transitions from a steep slope to less steep slope. In this region large debris from the steep section deposits as the velocity decreases. The channel continues to erode further downstream. A sawtooth pattern can be seen

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DESIGN AND FABRICATION  OF MINIATURIZED DIPLEXER FOR ANTENNA  APPLICATIONS

DESIGN AND FABRICATION OF MINIATURIZED DIPLEXER FOR ANTENNA APPLICATIONS

Conventional microstrip lowpass and bandpass filters such as stepped-impedance filter are widely used in many RF/microwave applications. In this proposed work,stepped-impedance filter type is used. In general design of microstrip lowpass filter involves two main steps. The first step in the design of microwave filter is to select a suitable approximation of the prototype model based on the specifications. Second is to calculate the order of the filter from the necessary roll off as per the given specifications.[3]

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Internal erosion under spillway rested on an embankment dam

Internal erosion under spillway rested on an embankment dam

Simple laboratory procedures are available to assess piping potential in cohesive materials, but no such methods exist for non-cohesive soil or rocks. In this research, piping type is categorized as internal erosion. According to Lane’s creeping factor, practical remedial measures which can be prescribed for this special case is to first: attaching a series of supportive walls to the right wall of spillway as Figure 6 and second: filling the piping hole with high quality cement. It is also observed Marlstone foundation is sensitive to piping

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A cluster randomized clinical trial of a stepped care intervention for depression in primary care (STEPCARE)  study protocol

A cluster randomized clinical trial of a stepped care intervention for depression in primary care (STEPCARE) study protocol

constraints, both human and material. For example, there is only about one psychiatrist to a population of one million people and the few available specialists are inequitably concentrated in urban settings [9]. It is gen- erally recognized that a way to minimize the conse- quences of this specialist manpower constraint is to integrate mental health (MH) into primary health care where services are mostly provided by non-physician primary health care workers (PHCWs). This strategy is much more likely to be viable and affordable because these resources already exist, are less expensive, and offer increased accessibility given that primary care clinics are closer to where people live. However this strategy is hampered by several factors: 1) inadequate training of the PHCWs, 2) lack of structured support and supervision for their work, and 3) competing duties [10]. The problem of lack of resources is further com- pounded by the inefficiency with which the limited avail- able resources are used. For example, treatments lacking any evidence are often offered and specialist time and skill are not efficiently deployed. A new model to ad- dress the treatment gap for depression must therefore give prominence to a more efficient way of deploying existing resources to deliver effective interventions. Stepped-care models seek to maximize efficiency by deploying available resources strictly according to needs, offering greater resources to those with complex or severe problems [11].

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The chronic disease management model for depression in primary care

The chronic disease management model for depression in primary care

way of organising care involves standardising the procedures and their indications, and has been used for the management of diverse conditions from diabetes and hypertension to addiction and back pain. A stepped care framework for providing identification and treatment options appropriate to the differing needs of people with depression has been adopted in the UK, and is integral to systems for depression care developed in health maintenance organisations in the US. The stepped care model advocated in the National Institute for Health and Clinical Excellence (NICE) guidelines (England and Wales) for depression is shown in box 3. Although it appears an effective and efficient way to deliver services, there is only limited evidence about the value of stepped care. In order to operate, several conditions should be satisfied (Bower and Gilbody 2005):

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Optimal management strategies for a cascade reservoir system

Optimal management strategies for a cascade reservoir system

The management and operation of a system responsible for the storage of a valuable commodity will always be a topic open for investigation and potential improvement, especially when the commodity is valuable enough to be referred to as“liquid gold”; water. Water reservoirs have long been employed around Australia and the globe to serve two main purposes; ensure communities have access to a reliable water supply during periods of limited rainfall or drought and to help protect communities from the impact of flood. This means that it is not only the operators of the reservoir sys- tems that are interested in their optimal management during these extreme events, but also the communities that rely upon the systems for one purpose or another. Therefore, this thesis aims to formulate and develop two mathematical models that can be employed to determine strategies for the optimal management of a cascade reservoir system under the two opposing extreme environmental conditions of a drought and flood. In this case, cascade refers to the unique layout of the reservoirs in the system, where releases from the spillway (termed spill) of a previous reservoir in the system become a source of inflows to subsequent reservoirs; thus influencing the volume of water, or storage level, of those subsequent reservoirs. Figure 1.1, provided at the end of this chapter, gives an example of the layout exhibited by a physical cascade reservoir system and how spill from one reservoir influences the storage level of the next.

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Stepped wedge cluster randomized controlled trial designs: a review of reporting quality and design features

Stepped wedge cluster randomized controlled trial designs: a review of reporting quality and design features

One possible CRCT design is the stepped wedge (SW); first proposed by Cook and Campbell [7], and first utilized in the Gambia Hepatitis Study [8]. In the SW-CRCT approach, the intervention is introduced over a number of time periods, with the order in which each cluster begins receiving the intervention determined at random. In the classical form of the design, all clusters begin in the control condition, and all receive the inter- vention by the completion of the trial, with all clusters actively taking part in the trial at each time period. Moreover, once a cluster switches to the intervention, it does not switch back to the control. However, whilst this latter feature remains common to all proposed SW-CRCT designs, recently numerous extensions have been proposed that, for example, allow some clusters to begin in the intervention, end in the control condition, or only actively take part in certain time periods [9].

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Design and Simulation of Folded Arm
Miniaturized Microstrip Low Pass Filter

Design and Simulation of Folded Arm Miniaturized Microstrip Low Pass Filter

In the Fig. 7 comparative results of S-parameter are made. In this graph, response of stepped impedance lowpass filter and proposed folded arm stepped impedance lowpass filter are compared. Both the filters show a cut-off frequency 1 GHz at -3 dB. Return loss of folded arm LPF is 10 dB higher than the stepped impedance LPF. Insertion loss of stepped impedance LPF is more than folded arm LPF. Both filter show a good stop-band response. Both filter show same stop-band range 1 GHz to 4.9 GHz.

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Stepped care for depression and anxiety: from primary care to specialized mental health care: a randomised controlled trial testing the effectiveness of a stepped care program among primary care patients with mood or anxiety disorders

Stepped care for depression and anxiety: from primary care to specialized mental health care: a randomised controlled trial testing the effectiveness of a stepped care program among primary care patients with mood or anxiety disorders

and/or referral to mental health care. All these interven- tions are evidence based but there is a lack of studies regarding the effectiveness of stepped care as a whole. Results of this study could offer encouragement for the implementation of an effective stepped care model. A major strength of this study is that it is a pragmatic ran- domised trial. In a pragmatic trial, patients and therapists are the same as those seen in daily practice. This means that the sample of patients may be quite heterogeneous (may have mild to severe depression/anxiety with or with- out psychiatric or somatic co-morbidity) and that the therapists (psychiatric nurses or psychologists) have aver- age qualifications (instead of top level therapists from an academic centre). This enhances external validity which means that the results of this study will reflect the 'real' effects of daily practice. If an intervention is shown to have a significant beneficial effect in a pragmatic trial then it has been shown not only that it can work, but also does work in real life [73].

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Step-Shaped Cavity-Backed Antenna and Wideband Wide-Angle Impedance Matching in Planar Phased Array

Step-Shaped Cavity-Backed Antenna and Wideband Wide-Angle Impedance Matching in Planar Phased Array

terrible in the band, and the VSWR is larger than 2. However, the two-stepped and three-stepped cavity-backed antennas can still obtain the bandwidths of VSWR < 2 from 7.66 GHz to 11.58 GHz and from 7.38 GHz to 11.89 GHz with the relative bandwidths of 41% and 47%, respectively. Hence, the impedance matching and bandwidth are improved when a stepped cavity is applied to the antenna at both the periodic boundary and free space. A two-stepped cavity-backed antenna is used for phased array construction in this paper.

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