Flap Gate Research Articles

Development of disaster prevention technology against tsunami and storm surge

A development of the flap gate type breakwater, which is based on a steel flap gate in hydraulic gates with a number of adoption results, are beginning to be adopted in actual construction. The flap gate type breakwater usually lies down on a seabed and rises up through a sea surface with buoyancy when tsunami or storm surge occurs. In past studies reflected viewpoints of a large number of specialists, it has been confirmed that the flap gate type breakwater has capabilities against tsunamis. This paper describes the characteristics of the flap gate type breakwater, the expansion of utilizations in seawalls except breakwaters to reduce tsunami and storm surge disasters.

Tersedianya Potensi Suplai Dan Drainasi Persawahan Danda Besar Melalui Revitalisasi Prasarana Hidraulik Tingkat Tersier

The low agriculture productivity at Danda Besar tidal swamp area is related with the existing water management system which is still at macro and meso level, and not fulfilling the paddy field water supply (micro water management system). Planting is carried out only in the wet season because the insufficient water management system does not provide available water supply in dry season. Impact of this problem include among others that the canal system become shallow and covered by vegetation. Quaternary canals are also not available. The selected location of this study is the Tertiary T2 Kanan Canal at Danda Jaya, a village in Kabupaten Barito Kuala, South Kalimantan province. These problems can be solved by water management revitalization and micro water management application equipped with a water regulator such as the Flap Gate. This study carrying out a 1 D hydraulic numeric simulation model in five scenarios by application of the DUFLOW computer program showed the improvement of canal capacity until adequate water is supplied during neap and spring tide. Thus, farmers can carry out a planting pattern twice a year in order to increase the crop production index from 100% to 150 – 200%.

Research on Design and Application of Flap Gate in Guiyang Nanming River

The core section of Guiyang Nanming River suffers from river water quality deterioration, black turbidity, sediment deposition and other phenomena. The deposition is extremely serious particularly at the upstream area in front of the flap dam. It is necessary to upgrade and transform the flap dam, thereby preventing the sedimentation in the front of the dam, and improving the ecological environment of the river. The flap dam should be newly designed, and its application should be studied.

Effectiveness Using Circular Fibre Steel Flap Gate As a Control Structure Towards the Hydraulic Characteristics in Open Channel

Hydraulic control gate structure plays an important role in regulating the flow of water in river, canal or water reservoir. One of the most appropriate structures in term of resolving the problem of flood occured is the construction of circular fibre steel flap gate. Therefore, an experiment has been conducted by using an open channel model at laboratory. In this case, hydraulic jump and backwater were the method to determined the hydraulic characteristics of circular fibre steel flap gate in an open channel model. From the experiment, the opening angle of flap gate can receive discharges with the highest flow rate of 0.035 m3/s with opening angle was 47°. The type of jump that occurs at the slope of 1/200 for a distance of 5.0 m is a standing jump or undulating wave. The height of the backwater can be identified based on the differences of specific force which is specific force before jump, F1 and specific force after jump, F2 from the formation of backwater. Based on the research conducted, the tendency of incident backwater wave occurred was high in every distance of water control location from water inlet is flap slope and the slope of 1/300 which is 0.84 m/s and 0.75 m/s of celerity in open channel model.

The optimal design of a flap gate array in front of a straight vertical wall: Resonance of the natural modes and enhancement of the exciting torque

We consider a wave energy converter made of an array of Q neighbouring floating flap gates with finite thickness in front of a straight vertical wall in constant depth. Solutions of the radiation and scattering problems are achieved by application of Green's theorem and Green's function yielding a system of hypersingular integral equations for the velocity potential expanded in terms of Legendre polynomials. We investigate how the distance between the array and the vertical wall affects the performance of the array under the action of monochromatic and random waves. We show that large values of the exciting torque on the gates can be obtained by tuning the wall distance with the resonance of the natural modes of the array; this in turn yields large power extraction for a wide range of frequencies.

津波・高潮減災のための技術開発

A devlopment of the movable flap gate type breakwater, which is based on a steel flap gate in hydraulic gates with a number of adoption results, is reaching the final stage of demonstration tests in the sea.The flap gate type breakwater usually lies down on a seabed and rises up through a sea surface with buoyancy when tsunami or storm surge occurs. In past studies reflected viewpoints of a large number of specialists, it has been confirmed that the flap gate type breakwater has capabilities against tsunamis. This paper describes the characteristics of the flap gate type breakwater, the expansion of utilizations in seawalls except breakwaters for tsunami and storm surge reduction.

WORKS WITH A MINIMUM ENVIRONMENTAL IMPACT IN RIVERBEDS

Various interventions need to be done in riverbeds for achieving certain goals (recreational, economic, flood prevention). However, they should have a low impact on river environments. This paper analyses the effects of a rise in the upstream water levels as an indicator of the impacts magnitude. We found that such an intervention can generate low impacts if it does no result in arise of the water levels. The study was carried out considering two rivers in the North East of Romania: Siret and Bahlui. The conditions in which various interventions can have low impacts were identified by analyzing two possible situations: a river water intake and a discharge sill with flap gate.

Influence of the Operating and Geometric Characteristics of a Bottom-hinged Flap Gate on the Discharge Coefficient of a Side Weir

Bottom-hinged flap gates on side weirs are often used for the regulation of flow diversion in case of water abstraction for a variety of needs. In this study, a new equation for the discharge coefficient of a bottom-hinged flap gate on a side weir was proposed on the basis of discharge measurements. The equation was divided into two parts. The first part covers the impact of the sharp-crested side weir and the second the influence of the position and the width of the flap gate. In this manner, the discharge coefficient can be calculated with other authors’ equations for a sharp-crested side weir, which then must be multiplied by the new proposed coefficient. Very good agreement was found between the obtained discharge coefficients and the one calculated with the proposed equation. Furthermore, the results were compared with the equations of other authors for the discharge coefficients of sharp- and broad crested side weirs. The agreement was found to be very good. Additionally, measurements of water levels along the edge of the flap gate and measurements of the velocity field were carried out with a computer-aided visualization method. From these measurements, it was possible to show that the contraction of the water jet varies with the gate-opening angle. It was also found that the side weir with a flap gate has the most favorable hydrodynamic shape around the gate-opening angle of 33°, where the discharge coefficient reaches its maximum.

Flap gate farm: From Venice lagoon defense to resonating wave energy production. Part 2: Synchronous response to incident waves in open sea

We consider a flap gate farm, i.e. a series of P arrays, each made of Q neighbouring flap gates, in an open sea of constant depth, forced by monochromatic incident waves. The effect of the gate thickness on the dynamics of the system is taken into account. By means of Green's theorem a system of hypersingular integral equations for the velocity potential in the fluid domain is solved in terms of Legendre polynomials. We show that synchronous excitation of the natural frequencies of Sammarco et al. (2013) yields large amplitude response of gate motion. This aspect is fundamental for the optimisation of the gate farm for energy production.

Flap gate farm: From Venice lagoon defense to resonating wave energy production. Part 1: Natural modes

We consider a flap-gate farm, i.e. a series of P arrays, each made by Q neighboring flap gates, in an infinitely long channel. We show that there are P × (Q − 1) natural modes and determine their eigenfrequencies and modal forms. When the distance between the arrays goes to infinity the eigenfrequencies converge to the Q − 1 values given by Li and Mei [14]. For an ad-hoc combination of channel geometry and flap gate characteristics, modal excitation can give significantly larger response than for the case of a single or a sparse gate system. This aspect is relevant for the design of an optimal gate farm wave energy converter.

The Application of Hydraulic Automatic Flap Gate in the Regulation Project of Duanmijian River

Informed by water pressure and gate weight balance principle, the hydraulic automatic flap dam makes use of hydraulic power together with the damping feedback system, which makes it possible to automatically open the discharge when water level at the upper stream is high and to close when the level is low. This helps to ensure that the water level at the upper stream always stays within the normal range and has been widely applied in city water regulation projects and hydropower renovation projects alike. The flap dam in the project reported here is constructed upon the existing levees of Duanmijian river. This paper discusses the design of the flap dam as well as the entire outline and its major features.

Easy and Efficient CSO Monitoring through a Flap Gate

Easy and Efficient CSO Monitoring through a Flap Gate

EXPERIMENTAL STUDY ON RESPONSE CHARACTERISTICS OF FLAP GATE BREAKWATER AGAINST WAVES

A flap gate breakwater is a new type structure for coastal disaster reduction; the breakwater usually lies down on a seabed and rises up through sea surface with buoyancy when tsunami or storm surge occurs. In past studies, it has been confirmed that the flap gate breakwater has capabilities against tsunamis. The characteristics of wave pressure acting on flap gate are different from those on a fixed gate and a breakwater since the flap gate moves according to acting waves or tsunamis. The present study examined the characteristics of wave pressure acting on the flap gate by hydraulic experiments using monochromatic waves and tsunamis. It was confirmed that the gate motion and wave pressure were closely related, and wave pressure was reduced by employing fluid resistance plates.

A simple approach for regulating saline groundwater inflows to natural streams in irrigated agricultural areas

Stream salinity management is of prime importance for ensuring environmental sustainability of rivers, streams, lakes and other water bodies. Saline groundwater inflows are the main cause of deteriorating quality of stream flows; especially during periods of low flows. The Murray-Darling Basin is a good example for reducing groundwater recharge from irrigated agricultural areas with successful implementation of land and water management plans (LWMPs). In most cases, these plans help minimize the influence of saline groundwater flows on the stream salinity, as a preventive measure. As a remedial measure, this paper introduces a simple but an innovative approach for regulating saline groundwater inflows to natural streams in irrigated agricultural areas. The approach uses the flap gate with an automatic lowering and raising mechanism. During low stream flow, this gate is kept in a raised position. Depending upon the upstream inflows, the ponding situation will develop hydraulic gradient away from the stream; groundwater inflows to the creek will become minimal. During high stream flows, the gate is kept in a lower position to let the diluted water flows through the stream uninterrupted. To install, operate and manage such gates on multiple sites along the stream(s), the individual control panels can be joined into a central control station via telemetric link up. This approach, which holds a key for successfully regulating groundwater induced salinity to natural streams, should be considered in conjunction with other LWMPs to improve stream salinity in an irrigated agricultural area.

Modified hemi-double-stapling technique combined with the temporal abdominal wall-lift method for performing Billroth I anastomosis after laparoscopically assisted distal gastrectomy

The authors have used a modified hemi-double-stapling (HDS) technique for reconstruction after laparoscopically assisted distal gastrectomy. The stomach is resected from the greater curvature side using a linear stapler inserted into the stomach from that side at a position vertical to the line of the greater curvature. Resection of the stomach is performed by extending the resection line to the lesser curvature using laparoscopic coagulating shears. The resected specimen is examined. After placement of a purse-string suture at the duodenal stump, an anvil is inserted into the stump, and an additional suture with 2-0 silk is placed over the purse-string suture. A curved intraluminal stapler (CDH25) is inserted into the stomach through the opening made on the lesser curvature side, and the center rod of the stapler is passed through the gastric wall on the corner of the resection line at the greater curvature. Ligation with 2-0 silk is added to the center rod by suturing the gastric tissue 5-8 mm from the center rod to encircle it. The authors call this the "one-knot setup HDS," and with this method, a large-caliber anastomosis is secured. In many cases, it is difficult to observe the anastomotic site through the small incisional opening. However, under laparoscopy with the temporal abdominal wall-lift method using the Multi Flap Gate, the anastomotic site can be easily and safely observed. One-knot setup HDS combined with the temporal abdominal wall-lift method is considered a safe and simple method for performing Billroth I anastomosis in laparoscopic distal gastrectomy.

フラップ式可動ゲートの津波低減性能に関する模型実験（その２）―起立安定化プレートの力学特性の把握―

The flap type gate is expected as one of new structures against tsunami, and we have kept developing it. In the past study, we have proposed a new mechanism of flap gate with the sway control plate, and confirmed that the modified flap gate worked enough for structures of disaster reduction. However, there are some uncertainties about both the dynamic characteristics of the flap gate with the plate and the hydraulic conditions accompanying the characteristics. In this study, two-dimensional hydraulic tests were carried out in a water channel with a wave generator, and the behavior of the flap gate was confirmed by measuring pressure and gate acceleration under several conditions. As a result, it is clarified that the modified flap type gate works effectively under some conditions.

Analysis of flows and water levels near tidal flap gate

A method is proposed for assessing the impact of rising sea levels on areas upstream of tidal flap gates. These devices, designed to allow drainage of surrounding land during low water and flood defence during high water, are commonly used in areas where tidal high water level is higher than the level of the land behind the sea wall. Studies were undertaken at Pagham Harbour, West Sussex, UK, where a number of tidal flap gates are used to control the flow of water from channels carrying drainage waters away from the nearby town of Chichester. On one of these channels, water level data were collected at 15-min intervals at three sites near the flap gate and analysed in order to obtain values over each tidal cycle of maximum and minimum water levels downstream of the gate, and the time of closure of the gate. Water level was also monitored at two locations upstream of the gate. By obtaining estimates of mean fresh water discharge for each tidal cycle, and combining these with peak tidal water level, a functional relationship (in the form of a three-dimensional plot) was obtained for the parameter tc, the length of time in hours for which the flap gate is closed during each tidal cycle. These values of tc were also used in conjunction with mean tidal fresh water discharge to produce another three-dimensional plot showing the effect on peak tidal water level upstream of the flap gate, thus providing an illustration of the sensitivity of local flooding to varying tc under different tidal conditions. Finally an estimate was made of the likely impact of a 300 mm rise in mean sea level on tc for the same set of fresh water flow data, using a set of ‘look-up’ tables based on the three-dimensional plots obtained. These indicated that the frequency of local flooding was likely to increase significantly for fresh water flows greater than 0·8 m3/s. Although the increase in local flooding illustrated here is not thought to be a cause for immediate concern, particularly in view of the recent construction of a further tidal flap gate adjacent to the existing one, nevertheless the methodology employed is applicable to similar systems.

Three-Dimensional Modeling of Fecal Coliform in the Tidal Basin and Washington Channel, Washington, DC

Fecal coliform are widely used as bacterial indicator in the United States and around the world. Fecal coliform impaired water is highly possible to be polluted by pathogenic bacteria. The Tidal Basin and Washington Channel in Washington, DC are on the Total Maximum Daily Load (TMDL) list due to the high fecal coliform level. To support TMDL development, a three-dimensional numerical model of fecal coliform was developed using the EFDC framework. The model calculates the transport of fecal coliform under the influences of flap gate operations and tidal elevation. The original EFDC code was modified to calculate the die-off of fecal coliform under the impact of temperature and solar radiation intensity. The watershed contribution is expressed as storm water inflow and the load carried by the runoff. Model results show that fecal coliform vary strongly in space in both the Tidal Basin and Washington Channel. The storm water only impacts a small area around the storm water outfall in the Tidal Basin and the impacts are negligible in the Washington Channel due to dilution. The water from the Potomac River may affect the fecal coliform level in the area close to the flap gate in the Tidal Basin. The fecal coliform level in the Washington Channel is mainly controlled by the fecal coliform level in the Anacostia River, which is located at the open boundary of the Washington Channel. The potential sediment layer storage of fecal coliform was analyzed and it was found that the sediment layer fecal coliform level could be much higher than the water column fecal coliform level and becomes a secondary source under high bottom shear stress condition. The developed model built solid connection of fecal coliform source and concentration in the water column and has been used to develop TMDL.

Stratification and fine sediment transport mechanisms in a semi‐enclosed tidal lagoon (Pagham Harbour, West Sussex)

AbstractPreliminary analysis of data collected at a macrotidal semi‐enclosed lagoon (Pagham Harbour, UK) has revealed useful information about long‐term patterns of siltation and some of the related mechanisms. Sediment surface‐level measurements made over 2 years at different sites within Pagham Harbour have shown a steady siltation, in common with earlier measurements, which is moderated by seasonal effects due to erosion by locally generated waves. Furthermore, inspection of vertical profiles of salinity and turbidity over individual tidal cycles has revealed that the degree of sediment transport on the flood tide is related to the vertical salinity gradient. Thus, at the Ferry Pool site, which is characterised by episodic pumped discharges from a nearby sewage treatment plant, landward sediment transport is enhanced by the high degree of salinity stratification observed during the flood tide. The mobility of the sediment, and the greater distribution of softer, less well‐consolidated sediment deposits, is greater here than at the other significant freshwater inflow at the Salthouse site, where the fresh water flow is instead moderated by a tidal flap gate. Preliminary analyses suggest that the higher the salinity stratification, the greater the landward sediment transport during the flood tide. Such analyses could help inform future policy on the methods of land drainage to macrotidal lagoons, and on the potential for managed realignment at such sites.

高潮・津波対策用フラップ式可動ゲートの伝達波低減機構の開発

The flap type gate against storm surge and tsunami has many superior points in comparing with existing coastal structures for prevention of disasters. However, the flap gate has the problem that the gate itself sways because of waves from the open sea and generates waves into a harbor. In this study, a new flap type gate was designed, and the wave transmission characteristics on a new gate were investigated through a two-dimensional hydraulic experiment with the model of scale 1/35. The obtained results indicated that the transmission waves due to sway of the gate were reduced.