Gate Slots Research Articles

Cavitation Investigation in the Sluice Section of the Sefid Rood Dam Using Flow 3D Software for Environmental Purposes

It is evident that water resources are essential for the existence of living organisms, particularly human life. Outlets are a series of structures employed to transfer water from the dam reservoir to the discharge point downstream. Due to the significance of this section of the dam, the performance analysis of the outlet, including the channel, gates, and their outlet, is sensitive. The presence of pressurized flow in the upstream of the outlet gate, energy dissipation due to various factors, and the very low values concerning the gate opening compared to the water head over the outlet gate cause significant errors in determining various parameters related to the outlets. This includes pressure drops across the gates and their discharge capacities when using theoretical methods. This research aims to investigate pressure distribution at various points along the outlet channel, determine the gate discharge capacity, and calculate its discharge coefficient. It explores the possibility of cavitation occurrence, compares the presented scenarios for post-service and emergency gate operations in the simultaneous operation of two gates, and determines the main loss coefficients in the channel, including frictional losses, conversion losses, and gate losses. This investigation utilizes data obtained from the physical model of the spillway outlet constructed at the Soil and Watershed Conservation Research Center laboratory. The physical model includes the channel and gates (service and emergency), and necessary experiments were conducted. The pressure values at different points, gate discharge rates at three opening levels (60%, 80%, and 100%), were measured in the reservoir, and the results are presented in corresponding tables and graphs. Additionally, the Flow 3D software was employed to numerically model the outlet discharge under three gate openings (60%, 80%, and 100%) for comparison between experimental and numerical results and with previous findings in this research. Subsequently, it will be demonstrated that, under single-gate operation and simultaneous operation, the cavitation index in critical areas, such as gate slots and between gates, in the single- gate mode falls within an acceptable range, practically eliminating the risk of cavitation. However, in simultaneous operation mode, negative pressures occur in some gate openings, posing the possibility of cavitation occurrence.

Damage characteristics and dynamic responses of high arch dams under rockfall impact loads

Rockfall is a typical natural disaster that is sudden, high in speed, unpredictable, and can easily adversely affect the structures. High arch dams are usually constructed in deep valleys, where rockfall is a typical destructive load. However, there is currently a lack of research on the effects of rockfall on the safe operation of high arch dams. Therefore, the Wudongde arch dam in China is selected in this paper for exploring damage characteristics and dynamic responses of high arch dams under rockfall impact loads. To improve the authenticity of numerical simulation, a coupled model is established based on the actual dam shape and terrain characteristics of the dam. The concrete damaged plasticity model is used for dam concrete and the rockfall is described by the JH-2 model to simulate mechanical properties of materials and reflect strain rate effects. The trajectories of falling rocks at the dam site are first investigated to analyze the locations where they may impact the dam. Based on the obtained results, two impact positions are considered possible in the analysis, namely, the dam crest and the gate slot, and then the nonlinear dynamic responses of the dam impacted by rockfall at different positions are compared. Finally, a sensitivity analysis is carried out to evaluate the influence of the rockfall properties on the damage characteristics of the dam. The results indicate that the trajectory and impact velocity of falling rocks are related to the falling height, rock size, and initial velocity. The rockfall impact on the dam crest has little influence on the safety of the dam for the robust mass dam concrete, while the track beam near the gate slot is vulnerable to rockfall impact. The damage degree to the structure is related to rockfall properties. Compared to larger-sized rockfalls, rockfalls with a diameter of 1 m cause minimal damage to the structure and have little impact on its safety. Higher impact velocity and stiffness of the rock lead to more severe damage, while the effect is relatively smaller compared to the rockfall size. The high stiffness also reduces the damage to the rock itself.

Decentralized Dynamic Scheduling of TCPS Flows and a Simulator for Time-sensitive Networking

Cybersickness and control-loop instabilities are two main concerns in Tactile Cyber-Physical Systems (TCPS). TCPS applications demand stringent bounds on end-to-end latencies to avoid their occurrences. Traditional best-effort networks cannot guarantee packet latencies in the presence of external traffic. However, emerging deterministic networks such as IEEE 802.1 Time-Sensitive Networking (TSN) can isolate time-critical flows from external traffic using IEEE 802.1Qbv Time-Aware Shaper (TAS) to guarantee bounded end-to-end packet latencies. In this work, we develop eDDSCH-TSN, a decentralized dynamic scheduling protocol to configure non-overlapping gate slots in TAS-enabled TSN switches to support TCPS flows. eDDSCH-TSN supports plug-and-play operation of compatible TCPS terminals with guaranteed minimal end-to-end packet latencies. Compared to the state-of-the-art, eDDSCH-TSN provides three orders lower end-to-end packet latencies for TCPS flows in mid-size networks with 10 hops between source and destination terminals. Further, we also present PYTSN, an open-source discrete-event TSN simulator that we use for evaluating eDDSCH-TSN. In particular, we use PYTSN to show the isolation of TCPS flows from external traffic and plug-and-play operation of TCPS terminals.

DDDMOSFET Performance Improvement by Gate Oxide Removal Followed by Silicided Source/Drain Formation in Gate Slots

In this work, the intentional insertion of slots in metal gate (MG) is introduced to solve the dishing issue for the double-diffused drain MOSFET (DDDMOSFET) fabrication. For traditional DDDMOSFET, the gate oxide layer in slots will be reserved to improve the device reliability, which requires an additional photomask to screen the gate/slot regions during the following sidewall formation and source/drain (S/D) implantation. This makes the process more complicated with increased cost. Without that additional photomask, it is proposed that the removal of gate oxide layer in slots can directly allow the floating S/D formation and the followed Ni silicidation there. It is demonstrated that such a novel process can not only relieve the MG dishing issue but can also effectively result in ~16% higher ON current and comparable OFF current for both N- and P-DDDMOSFETs without threshold voltage shift after applying electrical stress on gates. It is also revealed that the floating silicided S/Ds in slots have negligible influence on device breakdown characteristics. By saving one photomask, this work proposes a novel solution for the effective integration of core devices with very small feature sizes and high-voltage (HV) devices with large feature sizes in the same die, which is a common challenge for display driver chip fabrication using high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> /MG (HK/MG) technology.

FE analysis of the shaft lock chamber in Mengdigou Hydropower Project considering construction and service cases

The geological conditions of the diversion tunnel of Mengdigou hydropower station are very complex. Faults, joint fissures and groundwater are developed, and the underground chambers in the entrance end of the diversion tunnel are large scale, and the mechanical deformation induced by excavation and unloading is complicated. In order to investigate the stress and deformation in the shaft chamber surrounding rock during the period of construction and running, numerical simulation method was adopted to simulate construction process, discharging, water impoundment and power generation cases. The following conclusions are obtained: 1) during construction, the surrounding rock around the transition section of shaft lock chamber is stable; 2) during the period of discharging, water storage and power generation, the tensile stress in the inner part of the joint of gate slot, side wall and bottom plate exceeds the tensile strength of lining concrete. It is suggested to strengthen the reinforcement in these zones, and the concrete compressive stress in the compression area does not exceed the compressive strength. The results from this research could be taken as the reference for the design and construction of the project.

Reservoir Gate Based on Spiral Design

[Objective] aiming at the existing gate structure problem, a new type of spiral gate was designed. [Design] new spiral gate relates to the technical field of hydraulic engineering, including: support, driving device and gate body; The support is fixed on the dam body, and the driving device is fixed on the support body, which is used to drive the gate body to rotate, and at the same time, the gate body moves along the thread on the gate slot. [Results] the problem of poor sealing between gate gate and gate slot was overcome, and the sealing effect between gate and dam was improved. [Conclusion] the designed structure can provide some reference for solving the problems of existing gate structure.

Investigation on cavitation occurrence potential in Seymareh dam’s bottom outlet

ABSTRACT Cavitation phenomenon is one of the common problems of bottom outlets which convey high-speed flows. In the present study, the possibility of cavitation occurrence is numerically investigated. A numerical model is developed for the flow passing through bottom outlet using FLOW 3D software and K-ε (RNG) turbulent model. The model is operated for reservoir normal and maximum water heads also for various service gate openings. For normal head and different service gate openings, the research results show that cavitation indices are lower than the critical amount (0.2) on the conduit bed for 10%, 20%, 30%, 40%, 50%, 70%, and 80% service gate openings. Also, the side walls of conduit encounter with cavitation phenomenon immediately downstream of service gate for all gate openings. It is observed that the conduit top wall is free of cavitation damage hazard where the minimum cavitation index is equal to 0.46. At maximum reservoir head, the cavitation is not occurred inside the emergency gate slot and on its walls.

Application of computational fluid dynamics to predict hydrodynamic downpull on high head gates

PurposeHigh head gates are commonly used in hydropower plants for flow regulation and emergence closure. Hydrodynamic downpull can be a critical parameter in design of the lifting mechanism. The purpose of this paper is to show that a simplified two-dimensional (2D) computational fluid dynamics solution can be used in the prediction of the downpull force on the gate lip by comparison of computed results to experimentally measured data.Design/methodology/approachIn this study, ANSYS FLUENT CFD software was used to obtain 2D numerical solution for the flow field around a generic gate model located in a power intake structure which was previously used in an experimental study. Description of the flow domain, computational grid resolution, requirements on setting appropriate boundary conditions and methodology in describing downpull coefficient are discussed. Total number of 245 simulations for variable gate lip geometry and gate openings were run. The downpull coefficient evaluated from the computed pressure field as function of gate opening and lip angle are compared with the experimental results.FindingsThe computed downpull coefficient agrees well with the previous experimental results, except one gate with small lip angle where a separation bubble forms along the lip, which is responsible from this deviation. It is observed that three-dimensional (3D) effects are confined to the large gate openings where downpull is minimum or even reversed.Research limitations/implicationsIn large gate openings, three dimensionality of the flow around gate slots plays an important role and departure from 2D solutions become more pronounced. In that case, one might need to perform a 3D solution instead.Practical implicationsThis paper presents a very fast and accurate way to predict downpull force on high head gates in the absence of experimental data.Originality/valueAn extensive amount of simulations are run within the scope of this study. It is shown that knowing its limitations, 2D numerical models can be used to calculate downpull for a wide range of gate openings without the need of expensive experimental models.

Pressure Distribution of Pressure and Non-Pressure Sections of a Hydropower Station Spillway Tunnel

In this paper, we used VOF combining turbulent model to simulate pressure distribution of pressure section and non-pressure section in a hydropower station spillway tunnel with high head and large discharge in China. The results show that in the pressure section of the spillway tunnel, the values of pressure of emergency gate slot, working gate and the pressing slope, getting from physical model experiment and numerical simulation, are all positive. While in the non-pressure section, the No.1、2、3 aerators of the sudden enlargement and sudden drop occur the maximum pressure. And at the back of the No.1、2、3 aerators, where the values of pressure are negative, forms cavity. The conclusions obtained can improve the design of spillway tunnel.

Numerical Simulation on Fluid-Solid Coupling of Gate with Different Structure Types of Hemline in Deep Hole

Although there are some achievements of flow-induced vibration of plane steel gate, few is about the influence on gate caused by the difference of structure types of gates hemline. This paper studies on the flow pattern, natural vibration characteristics and dynamic response of four typical types of gates hemline in deep hole of Kajiwa Hydropower Stations service gate. Based on model test and numerical simulation and considering the flow pattern under the gate and in the gate slot, the natural vibration characteristics and the gates dynamic response, it is suggested to use an anteversion angle and a caster angle (type D for short) for the hemline of the type II gate slot. The optimal factors of a gates hemline in a concrete project can be optimized by numerical simulation.

Numerical Simulation on Fluid-Solid Coupling of Gate with Different Structure Types of Hemline in Deep Hole

Although there are some achievements of flow-induced vibration of plane steel gate, few is about the influence on gate caused by the difference of structure types of gates hemline. This paper studies on the flow pattern, natural vibration characteristics and dynamic response of four typical types of gates hemline in deep hole of Kajiwa Hydropower Stations service gate. Based on model test and numerical simulation and considering the flow pattern under the gate and in the gate slot, the natural vibration characteristics and the gates dynamic response, it is suggested to use an anteversion angle and a caster angle (type D for short) for the hemline of the type II gate slot. The optimal factors of a gates hemline in a concrete project can be optimized by numerical simulation.

Pressure fluctuations and cavitation index in the slot of lift bottom outlet gate, by using a physical model and introduction of normal standard distribution formula

The high velocity flow of water along with the severe head loss causes several turbulences and may lead to occurrence of cavitation phenomenon in hydraulic structures and severe destruction in some parts of them. Flow separation within the slots make eddies and vortices, which can also create cavitation. This study deals with the pressure fluctuations which are product of current severe turbulence, their processes and cavitation phenomenon at the gate slot region (with length/wide ratios of 2 and a 45o angle to the edge of the vertical-gate) of physical model of bottom outlet of Gotvand Olya storage dam. The study was conducted at the gate openings of 10, 30, 50, 70, and 100% and in different 2, 3 and 4 meter-heads and at0.1 %probability levels. Data collected using a transducer, were then transferred to an amplifier, and finally recorded in a computer. The results obtained indicated that at the gate openings of 30%, 50% and 70%, risk of cavitation occurrence is the maximum and at 10% and 100% it is the minimum. Also the piezometer, closest to the gate edge, is subjected to more fluctuations and critical point of pressure fluctuations are transferred to higher points upon with increase of gate opening. Coefficient of pressure fluctuations (C\'p) is the maximum at10 % opening that indicates compaction and pressure beats to the structure in this opening. Therefore control hydraulic conditions and geometric changes of the gate slot decreasing cavitation occurrence to the minimum would be possible. Keywords: Bottom outlet, Cavitation, Coefficient of pressure fluctuations, Gate slot

Pressure Fluctuations and Cavitation Index in the Slot of Lift Bottom Outlet Gate, by Using a Physical Model and Introduction of Normal Standard Distribution formula

The high velocity flow of water along with the severe head loss causes several turbulences and may lead to occurrence of cavitation phenomenon in hydraulic structures and severe destruction in some parts of them. Flow separation within the slots make eddies and vortices, which can also create cavitation. This study deals with the pressure fluctuations which are product of current severe turbulence, their processes and cavitation phenomenon at the gate slot region (with length/wide ratios of 2 and a 45° angle to the edge of the vertical-gate) of physical model of bottom outlet of Gotvand Olya storage dam. The study was conducted at the gate openings of 10, 30, 50, 70, and 100% and in different 2, 3 and 4 meter-heads and at 0.1 % probability levels. Data collected using a transducer, were then transferred to an amplifier, and finally recorded in a computer. The results obtained indicated that at the gate openings of 30%, 50% and 70%, risk of cavitation occurrence is the maximum and at 10% and 100% it is the minimum. Also the piezometer, closest to the gate edge, is subjected to more fluctuations and critical point of pressure fluctuations are transferred to higher points upon with increase of gate opening. Coefficient of pressure fluctuations (C'p) is the maximum at 10 % opening that indicates compaction and pressure beats to the structure in this opening. Therefore control hydraulic conditions and geometric changes of the gate slot decreasing cavitation occurrence to the minimum would be possible.

Cavitation study in bottom outlet gate slots by pressure fluctuation

Around the high head gates as the velocity is too high, every non uniform object such as a slot makes the flow too disturbed. Vertical-lift gate required recessed slots in abutments for the movement of the gate slides. The flow of water across the slots causes flow separation at the upstream lip of the slot and reattachment on the downstream side. Eddies are set up within the slots and vortices are formed. Thus, under higher velocity flow conditions (due to high head), cavitations can occur within gate slots by fluctuations. In addition of cavitations the pressure fluctuation can make impacts on the structure too. This hydraulic phenomenon can be occurred with serious damages. In this research, experimental data is used based on measuring pressure fluctuation by pressure transducer under an experimental model which has built and taken place in Michelle Hydraulics Laboratory at civil engineering department of the University of Melbourne. Pressure fluctuations were measured under two group of seven piezometers along the two gate slots for gate positions of 10%-10%, 30%-10%, 50%-10%, 70%-10%, 30%-30%, 50%-30%, 70%-30%, 50%- 50%, 70%-50%, 70%-70%, head condition behind the gates were constant for all tests. The results were analyzed and presented as Cavitations Index in two slots. The cavitation indexes were calculated in based 0.1% probability levels of fluctuation pressures. Other probability levels contained 1%, 5% as higher pressures and 95, 99 and 99.9% as higher pressures, were studied in this paper.

Cavitation study in bottom outlet gate slots by pressure fluctuation

Cavitation study in bottom outlet gate slots by pressure fluctuation

Investigation of Deflector Effect on Cavitation in an Axisymmetric Gate Slot by Means of AE Measurement

To take up the three-dimensional axisymmetric gate slot concerining with the gate slot possessed in hydraulic equipment, such as, a gate valve, the state of cavitation of the gate slot was investigated by Acoustic Emisson (AE) measurement. The relationship between AE energy level and cavitation condition was analyzed by the root-mean-square (RMS) of acoustic wave. Moreover, a new AE parameter "relative accumulated intensity (RAI)" was defined in order to estimate the erosion tendency of cavitation. Combining with the result of impulsive pressure measurement, the relationship between the erosive damage and the high amplitude generation of AE wave is confirmed by using RAI. In consideration of deflector effect, the AE measurement showed that the conical shape installed on the upstream side of gate slot makes the cavitation erosion increased, and the offset shape on the downstream side of gate slot makes the cavitation erosion decreased significantly.

Experimental Study on the Shear Failurelaw of Gate Slot

The mechanical behavior of 12 concrete specimens under local strain is studied according to simulating principle of work of gate slot. The experimental result indicates that the failure mode of these reinforced members in the test has revealed to be shear failure. The shear failurelaw of gate slot based on the test data is analyzed in the paper, and the main effect factors of the shearing capacity of gate slot are discussed. In this foundation, a corresponding proposed simplified method is put forward in the end.

Study of the Free Surface Flow on an Ogee-Crested Fish Bypass

A study of the free surface flow on an ogee-crested fish bypass is presented. The commercial computational fluid dynamics (CFD) code Fluent 6.1 was used to perform the simulations. Structured/unstructured hybrid grids were used to accommodate the complex geometry that included gate slots, flow control gates, and an aeration slot. The volume of fluid (VOF) approach was used to model the water/air interface. The fish bypass exhibits complex free surface features including free nappes and air entrainment from the air slots. Free surface elevations on both sides of the nappe, pressure along the ogee surface, and discharge rating curves were compared against 1:24 experimental data from the laboratory model for different headwater elevations and gate settings. Limited comparison against measured velocities was also performed. Once deemed reliable through validation against experimental data, the computational model was used to analyze the flow field, supplementing the areas of limited experimental data. Though the paper presents the final fish bypass design, CFD was used to guide the design process and provide insight for several variations in the geometry.

Diversion tunnel of the Irganaiskaya waterworks facility and prospects of its use in the period of erection of the dam to intermediate levels

General information on the diversion tunnel and statement of the problem of its use at normal maximum operating level NMOL = 521 m. The Irganaiskaya waterworks facility is being built in Dagestan on the Avarskoe Koisu River. The design engineering solutions for this waterworks facility and the stage of the construction have been considered in [1]. Excess water volumes of this waterworks facility are passed through the right-bank combined diversion and operational tunnel-kind spillway designed for freeflow operation in all stages of flow passage. The diversion tunnel is the first story of the spillway, which serves for passing flows in the initial period of the erection of the waterworks facility and in temporary operation. This structure consists of an intake channel, intake portal, slightly inclined part of the tunnel, and a tail device. The gretaer part of the slightly inclined tunnel and the tail device are to be used later in the period of continuous operation after the erection of the sluiceway entrance and inclined part of the sluice of the upper (second) story. Some data on the structure of the diversion tunnel and of laboratory hydraulic studies performed for its design are presented in [2]. The full length of the diversion tunnel is 965 m, and a two-span gates chamber is constructed in its intake portal (Fig. 1). The sizes of the entrance cross-section of the gates chamber (in front of the slots of the guard gates), which determine the diversion capacity of the tunnel, are h b = 6 4.5 m; the sizes of the main gates are 6.3 3.5 m. The operating gates were actuated by hydraulic actuators mounted at a level of 522.0 m of the upper part of the intake portal of the tunnel. Metallic facing exists in the gates chamber only on the zone adjoining the gate slots. Behind the gates chamber and the bottleneck transition part, the tunnel has a trough shape with a height of 11 m and a width of 8 m; the interface of the trough and of the vertical side walls of the tunnel is rounded. On the upstream region (in front of the connection between the tail reach of the tunnel and the inclined conduit of the operational spillway) the tunnel has a sloped bottom (the slope is 0.006) and on the downstream discharge region the slope is 0.0235. In the greater part of the length the diversion tunnel is made of concrete of class B30, but in the upstream region the Power Technology and Engineering Vol. 39, No. 6, 2005

114 戸溝内に発生するキャビテーションに及ぼすデフレクタの効果(流体 III,2.学術講演)

114 戸溝内に発生するキャビテーションに及ぼすデフレクタの効果(流体 III,2.学術講演)