Bottom Of Canal Research Articles

Numerical simulation and optimization of a circular open channel for fish farming using Computational Fluid Dynamics (CFD)

Open canals are one of the most common and cost-effective methods in water supply networks; they are widely used in different industries such as agriculture, water and sewage treatment, urban drainage, pisciculture and water parks. Due to global warming, the demand in clean energy to replace fossil fuels has caused using water turbines in riverbeds and aqueducts to be important. On this basis, optimizing key parameters such as flow motion and canal turbulence is crucial to reduce breakdowns while designing canals. In fact, the inappropriate adjustment of velocity and pressure within the canals may lead to the system failure: imbalance between inlet and outlet will increase the water level and the pressure on canal walls thus, leading to breakdown. In this paper, a circular open canal was designed for a pisciculture system. The velocity and height of the water canal is controlled by the canal inlet and outlet system and the water flows continuously inside the canal. By keeping the canal water volume constant in any time and the flow motion with constant velocity, the system makes the fishes feel infinite movement. Furthermore, the water particles and impurities (e.g., food and fish feces) are removed by the outlet from the canal bottom, transferred to the filtration system, and returned to the fish farm by the canal inlet after the filtration procedure; the mentioned technique causes the water canal to be kept at its optimal level. Computational Fluid Dynamics (CFD) has been used to simulate the canal flow. Solving the Navier-Stokes equations numerically and assuming incompressible, unsteady, and two-phase flow, the parameters of the canal flow were extracted. Also, by mounting the system outlet along the path of water movement, greatly reduces the adverse effects of the outlet suction force on the canal main flow. Moreover, by dividing the canal inlet with guide vanes, the inlet has been modified for the entrance of the clean water simultaneously with the distribution of the inlet flow to several smaller flows in order to make the canal water continue to move continuously without any turbulence.

Расчетное исследование потерь воды из необлицованных каналов с учетом геолого-почвенных особенностей севера Калмыкии

Purpose: carrying out filtration calculations of the main canals (MC) and comparison (comparative analysis) of the obtained values. Materials and methods. The object of study is the water supply network of the Sarpinsky irrigation and watering system (SOOS) in the North of Kalmykia. The initial data for the study were the field survey data of the system canals, as well as materials for official use obtained in the operating organization. When performing filtration calculations, the physical and geographical features of the irrigation network location area were taken into account and the method for calculating backed fil-tration from a canal (in an earth channel) was used under conditions of a steady movement of the seepage discharge. The calculation was based on the application of the filtration resistance method. Results and discussion. Taking into account the features of the geological and soil conditions of the northern regions of Kalmykia, the calculated values of filtration losses from the MC system were determined, which amounted to 2.7–6.51 l/(day sq. m) for the calculated sections of the MC VR-1 and 5.46 l/(day sq. m) – for MС R-1. Comparison of the data ob-tained for the MC SOOS with the results of studies of unlined sections of the Great Stavropol Canal, laid in the similar geological conditions, confirmed the authors' assumption that the values of seepage flow rates from the MC were significantly affected by the presence of clay soils at the canal bottom. Conclusions. As a result of the research, it was found that the value of filtration losses from MC SOOS is significantly affected by the geological and soil features of the system location area, and in particular the low permeability of mantle loams, as well as the presence of impervious Khvalyn clays of marine origin. The studies of other authors have confirmed that the close occurrence of these clays to the day surface contributes to flooding and land salinization, this was not taken into account when developing irrigation in the north of the region.

Development of an undershot cross-flow hydraulic turbine resistant to snow and ice masses flowing in an installation canal

This study developed a microhydraulic turbine that can stably and efficiently generate electricity even in canals where snow and ice masses frequently flow down. An undershot cross-flow hydraulic turbine was selected as the development target, and experiments were conducted in an irrigation canal in a heavy snowfall area. Spherical snowballs were made to flow down to the turbine from the upstream direction. The behavior of the snowballs and the power generation performance were investigated as these snowballs passed through the rotor. When the diameter of the snowball is smaller than the blade interval of the rotor, the snowball passing through the rotor causes a small decrease in power output. In contrast, when the diameter of the snowball is larger than the blade interval, the snowball is entrained between the rotor and canal bottom, temporarily stopping the rotor, and resulting in a large decrease in power generation. These results suggest that an undershot cross-flow hydraulic turbine can reduce power generation performance due to snow and ice masses when its blade interval is larger than the expected size of the snow and ice masses. This study developed some design guidelines for this turbine that are highly adaptable to snow- and ice-flowing irrigation canals.

Analysis on water migration in freeze-thaw process of composite lining canal in seasonal frozen soil area

In order to quantify the migration rule of water in composite lining canal foundation soil during the freeze-thaw process, the outdoor prototype test is performed to prove the change rules of water in different positions and depths of the rigidflexible mixed composite lining canal foundation during the whole freeze-thaw cycle. The prototype observation test shows that during the freezing period, the water content within the 0~80cm depth of the canal foundation soil increases with the depth, and that within the depth of 80~160cm decreases gradually with the depth. In the freezing period, water accumulates in the depth of 60 ~ 80cm, with a maximum water transfer amount of +13.2%, which occurs at the canal bottom. In the thawing period, the maximum water content also occurs at the canal bottom, with a maximum water transfer amount of -11.0%. Through the laboratory test of soil samples, the water migration development and change rules of the canal foundation soil, under different moisture contents and temperature gradients are studied in unilateral pattern. In the case of the same top plate control temperature, soil samples with similar initial water contents have similar water transfer amounts. The samples with higher initial water content have higher water transfer amount, with higher water accumulation, normally accumulating in the depth of 16~18cm. The results indicate that high water contents make it easy to gather water in soil samples during the freezing period.

A fully coupled three-dimensional numerical model for estimating canal seepage with cracks and holes in canal lining damage

Concrete and geomembranes are common materials used in canal linings to decrease canal seepage. Current numerical studies focus on concrete linings only by equivalent continuous models and seldom are about geomembrane and are suitable to quantify the seepage loss from canals with damaged linings. In this study, a new model is developed for the coupled numerical simulation of seepage through concrete with cracks and a geomembrane with holes in canal lining damage based on the finite element method. In this model, the porous media is discretized into solid elements, whereas discrete cracks and geomembranes are modelled by zero-thickness elements, with the Richards equation and cubic law applied to describe the water seepage process. The porous media and crack zones are implicitly coupled in time and space through the exchange flow between the concrete and the crack zones in that the heads are integrated in a single matrix equation. The domain area is divided into two subdomain areas by the geomembrane. For the two subdomain areas, the surfaces of both sides in the geomembrane are treated as two flux boundaries. The proposed model is calibrated and validated by the results of ponding tests conducted on a canal with four lining treatments and additional experiments, which showed that the model fit the experiments very well. The model is applied to sensitivity analyses by varying the model parameters. The model is shown to be capable of simulating the seepage of canals lined by concrete and geomembrane lining with different cracks and holes. The sensitivity analysis shows that canal seepage mainly depends on the lining characteristics, such as the crack width, hole density, saturated hydraulic conductivity (Ks) of the geomembrane, Ks of the concrete, and Ks of the soil layers adjacent to the canal bottom.

Технология укладки бентонитовых матов на канале в сложных условиях производства работ

Purpose: the technology of laying geocomposite bentonite mats with the creation of an anti-filtration lining of increased reliability on the main canal section made under difficult conditions (in the presence of karst and suffusion phenomena) is considered. Materials and methods. The theoretical basis of the research is the indicators of physical, mechanical and technical characteristics of bentonite mats of various manufacturing companies. The practical component is flow charts, diagrams and technology for the work performance in natural conditions on the main canal section. Results and discussion: to reduce the filtration coefficient of anti-filtration coatings it is advisable to use two- and three-layer materials, which were used in the reconstruction of the Donskoy main canal section instead of polymeric materials, according to the results of the feasibility study. The work on laying sodium bentonite mats was carried out in difficult conditions after stopping the water supply, when there was an intense slope sloughing, and the water level in the canal was set below the groundwater level in the canal zone. At the same time, the canal was periodically cleaned with a dredger to remove the swollen soil along the canal bottom, and on the slopes – excavation with a dragline excavator, followed by transportation and soil storage in the slurry dump maps. Further, the work was carried out on maps with pools, separated by dams, where map sections were drained by a mobile pumping station. Conclusions: the use of the developed technology for canal cleaning and laying roll materials based on bentonite made it possible to reconstruct successfully the most dangerous canal sections. The introduction of a structural and technical solution in the form of a combined screen design ensures almost complete water imperviousity of the bottom and slopes of the canal.

An Experimental Study on Concrete and Geomembrane Lining Effects on Canal Seepage in Arid Agricultural Areas

Canal lining is commonly used to reduce seepage loss and increase water use efficiency. However, few studies have quantitatively estimated the seepage control effects of different lining materials under different service times. Ponding tests were conducted on the same canal section with four different lining statuses to investigate the canal lining effect on seepage control and its impact factors in arid areas. The cracks and holes in different lining materials were surveyed, and the canal seepage rates under the four test treatments were calculated by monitoring the water level change in the canal. The results show that the cracks in the joints of the two precast concrete slabs and holes in the geomembrane, which are located 0.25 m above the canal bottom on two sides of the canal, are responsible for the increased seepage loss. The new concrete and geomembrane lining combination reduces seepage by 86% compared with no lining, while seepage can be reduced by 68% using the concrete and geomembrane lining combination after three service years, and the amount decreases to 11% by using geomembrane lining with a three year service time. Based on the experiment and literature, a statistical relationship between the seepage reduction and lining service time was established, which provided a possible and easy way to estimate seepage losses from lined canals and improve the estimation accuracy using an empirical formula. Without considering the service time lining effect, the seepage loss is underestimated by 58%, and the canal water use efficiency is overestimated.

Understanding Water Flows and Air Venting Features of Spillway—A Case Study

For safe spillway discharge of floods, attention is paid to the water flow. The resulting air flow inside the facility, an issue of personnel security, is sometimes disregarded. The spillway in question comprises two surface gates and two bottom outlet gates lying right below. Air passages to the outlet gates include an original gallery and a recently constructed vertical shaft. To understand water-air flow behavior, 3D CFD modelling is performed in combination with the physical model tests. The simulations are made with fully opened radial gates and at the full pool water level (FPWL). The results show that the operation of only the bottom outlets leads to an air supply amounting to ~57 m3/s, with the air flow rates 35 and 22 m3/s to the left and right outlets. The air supply to the right outlet comes from both the shaft and the gallery. The averaged air velocity in the shaft and the gallery are approximately 5 and 7 m/s. If only the surface gates are fully open, the water jet impinges upon the canal bottom, which encloses the air space leading to the bottom outlets; the air flow rate fluctuates about zero. If all the four gates are open, the total air demand is limited to ~10 m3/s, which is mainly attributable to the shear action of the meeting jets downstream. The air demand differs significantly among the flow cases. It is not the simultaneous discharge of all openings that results in the largest air demand. The flood release from only the two outlets is the most critical situation for the operation of the facility. The findings should provide reference for spillways with the same or similar layout.

Behavioural responses of eel (Anguilla anguilla) approaching a large pumping station with trash rack using an acoustic camera (DIDSON)

AbstractEuropean eel, Anguilla anguilla L., migrating to the sea encounter many man‐made structures that can hamper and delay migration or induce mortality. Studying small‐scale behavioural movements in front of these man‐made structures could provide insight in further mitigating adverse effects. The behaviour of eel approaching a trash rack in front of a large pumping station was investigated using a dual‐frequency identification sonar (DIDSON). Eels approaching the trash rack swam through the rack (40.5%) but also showed turning behaviour at (44.7%) or in front of the rack (14.7%). Eels approaching the rack had varying body positions, predominantly head or tail first, but also curled up into a ball or drifted sideways. After turning in front or at the trash rack, eels showed upstream and downwards swimming towards the canal bottom. The results suggest a stepwise response to potential cues, when firstly the body position is changed in such a way that secondly, later on, enhances eventual fast upstream escapement when perceived necessary. Implications for management of these behavioural observations are discussed.

Optimum layout of weep holes in concrete irrigation canals to control uplift pressure and hydraulic gradient

In this study, the effect of weep holes on controlling uplift pressure and hydraulic gradient under concrete canals was investigated in different groundwater levels. For this purpose, three weep holes were embedded in different locations and combinations on the bottom and the sidewall of a laboratory canal. The amounts of seepage discharge were measured from these weep holes in single and combined modes. The corresponding values of seepage discharge, uplift pressure, and exit hydraulic gradient were calculated through simulation with the Seep/W model. The comparison of the observed and the simulated seepage values was indicative of the model’s high accuracy with a mean error of 6.23%. The results showed that uplift pressure values in the single modes of weep holes in three different groundwater levels are similar. Uplift pressure in the binary combinations had a significant reduction compared to the single modes (an average of 73%). The maximum exit hydraulic gradient occurred at the weep hole located at the corner of the canal bottom. In general, the binary combinations of the weep holes were the best choice in terms of the minimum uplift pressure and the suitable exit hydraulic gradient.

Ecological thresholds of hypoxia and sedimentary H2S in coastal soft-bottom habitats: A macroinvertebrate-based assessment

Ecological thresholds of dissolved oxygen (DO) and sedimentary hydrogen sulfide (H2S) for macrozoobenthos were examined during a 30-month monitoring of two stations in a highly eutrophic canal in inner Tokyo Bay, Japan. Bottom DO and H2S concentrations fluctuated seasonally, and were significantly correlated with water and sediment temperatures. Red tide-derived phytodetritus was a major source of sediment organic matters in the canal bottom, and the sediment became highly reduced and sulfidic condition in warmer months (sedimentary H2S; up to 8.5 mM). Dominant opportunistic taxa, including polychaetes and amphipods, were eliminated under low DO and high H2S conditions (i.e., population thresholds), and devastation of community structure occurred at 2.4–3.3 mg l−1 DO and 1.8–2.7 mM H2S (i.e., community thresholds). To maintain ecosystem function in anthropogenically degraded habitats and ensure colonization by macrozoobenthos throughout the year, DO and H2S levels should be maintained below these thresholds.

Malezas asociadas a canales de riego y terrenos colindantes de arroz anegado en Finca El Cerrito, Guanacaste, Costa Rica.

A weed survey was conducted on irrigation canals and neighboring inundated rice fields, at Finca El Cerrito, Liberia, Guanacaste, Costa Rica. Sampling was performed on two growing seasons contrasting in weather conditions (rainy and dry) during 1992. Each surveying point was subdivided in five habitats (levee, internal slope, external slope, bottom of canal, and neighboring rice field). Plant species, percent cover and phenological stage were recorded at each habitat. In addition, for each species the next parameters were estimated: Frecuency-Cover Index (IFC), and Relative Participation Index (IPR). IPR at the family level was also calculated. 131 species during the dry season, and 144 species during the rainy season were recorded, showing that there is a significant plant diversity associated to these irrigation canals. The levee showed the greatest amount of plant species, while crop fields the least. Poaceae was the most important family, followed by Cyperaceae, based on IPR. Echinochloa colonum showed high IFC values and appeared in all habitats; this species together with others such as Oryza rufipogon, O. latifolia, Cyperus iria, and several broadleaf weeds are carefully controlled in rice fields, but reproduce heavily on irrigation canals, and shed their seeds in irrigation water, thus reinfesting commercial fields.

Research on Elastocoast Revetments Frost Heave Adaptability Model Test

Elastocoast revetments frost heave adaptability model test was carried out. Conclusions: (1) Elastocoast revetments can increase heat resistance and decrease the energy transfer. So the frozen depth and amount of frost heaving could be reduced. (2) This structure has deformation characteristics with temperature, and has a deformation at the test beginning. (3) The freezing rate under revetments is slow and the water supply is sufficient, because of which the amount of frost heaving will occur at one third of side slopes of canal, and the bottom of canal take the second place. (4) Consolidation settlement occurred after freeze-thaw cycling. And the revetments have a trend of becoming gentle slope. It indicates that Elastocoast revetments can commendably adapt to frost heave deformation. (5) The freeze-thaw durability is influenced by water content and the dosage of Elastocoast. The capability to resisting freeze-thaw denudation is better with the water content reduce and the material dosage increase.

Impact of hydrodynamics (ex- and infiltration) on the microbially controlled phosphorus mobility in running water sediments of a cultivated northeast German wetland

To gain insight into the impact of hydrodynamics (ex- and infiltration) on microbial activities, the microbial community structure, and the dynamics of phosphate and other chemical parameters in running water sediments of two transects in a German wetland have been studied. Flow directions and Darcy flow rates at canal bottom were determined using temperature profiles in the groundwater zone near and beneath the canal. Besides the chemical composition of pore water and sediment, a suite of enzyme activities and phosphorus fractions have been analyzed in the sediment. Hydrological analysis proved that at one transect infiltrating and stagnant conditions alter frequently, whereas at the other transect exfiltration dominates. We found significant differences between the transects in microbial activities and organic and iron-bound phosphorus as well as significant correlations between Darcy flux, microbial activities and phosphorus fractions. We conclude that not only the direction and rates of the flow, but also the quantity of changes between ex- and infiltration have an impact on microbial activity, and thus on phosphorus dynamics in the sediment of wetlands.

An integrated approach for modeling solute transport in streams and canals with applications

A new modeling approach for solute transport in streams and canals was developed to simulate solute dissolution, transport, and decay with continuously migrating sources. The new approach can efficiently handle complicated solute source feeding schemes and initial conditions. Incorporating the finite volume method (FVM) and the ULTIMATE QUICKEST numerical scheme, the new approach is capable of predicting fate and transport of solute that is added to small streams or canals, typically in a continuous fashion. The approach was tested successfully using a hypothetical case, and then applied to an actual field experiment, where linear anionic polyacrylamide (LA-PAM) was applied to an earthen canal. The field experiment was simulated first as a fixed boundary problem using measured concentration data as the boundary condition to test model parameters and sensitivities. The approach was then applied to a moving boundary problem, which included subsequent LA-PAM dissolution, settling to the canal bottom and transport with the flowing canal water. Simulation results showed that the modeling approach developed in this study performed satisfactorily and can be used to simulate a variety of transport problems in streams and canals.

Hydrodynamic and sediment transport modelling in the canals of Venice (Italy)

A framework of numerical models was applied to the canal network of Venice in order to simulate hydrodynamics and sediment transport. A two-dimensional finite element model (SHYFEM) was applied to the whole surrounding lagoon using water levels as a forcing. The computed levels were extracted along the contour of the city of Venice and then a link-node model was run in the canal network. The simulated variables were calibrated and compared with data from field measurements. Calculated water elevation displays a good agreement with the measured data, and current velocity is well reproduced. Simulations were initially carried out using a constant Manning parameter (MC) and successively a varying coefficient (VMC) was adopted, in order to account for the different depths of the canals. By applying the sediment transport module an evaluation of the sediment accumulation rate in the canal network was obtained, permitting an estimation of the yearly silting up of the canal bed. Different simulations were carried out considering material input from both the city and the lagoon. The model is able to reproduce the overall accretion rate of the canal bottom, and it is a useful tool for planning the dredging activities in the whole canal network.

New record of the species Spongilla lacustris L. (Porifera)

The species Spongilla lacustris was identified for the first time in Iraq, it was found during winter 1998 in an irrigation canal within the campus of the University of Baghdad (Jadiriah), water is drawn from Tigris river. The specimens were found in water samples of sizes ranging between 5-50 cm with yellowish color . It was found in two habitats , one as attached on submerged aquatic plant Ceratophyllum sp., and the other on the canal bottom (concret material). Some physico- chemical characters were determined including conductivity ,salinity , pH, total alkalinity, total hardness, Ca ,Mg ,anddissolved oxygen. Water quality was fresh , alkaline, hard and well aerated.

THE SEAGOING HOPPER DREDGE

Dredging is a special type of excavation involving the removal of material from under water. Several thousand years ago the Chinese and the Assyrians employed the primitive spoon-and-bag dredger to clean and maintain their canals. This apparatus consisted of a bag manipulated from a boat by means of a pole attached to a yoke or hoop at the mouth of the bag which was dragged along the canal bottom. When full, the bag was lifted and dumped into the boat. The method of disposal of the material is not clear, but it must be assumed that it was lifted ashore or dumped overboard, all probably by hand. Little improvement over this spoon-and-bag method of dredging was made until the advent of the industrial era in the eighteenth century. The method was then developed into a chain of buckets moving on a ladder.