Hydraulic Water Research Articles

Development of a Six-Degree-of-Freedom Deep-Sea Water-Hydraulic Manipulator

With the advancement of deep-sea exploration, the demand for underwater manipulators capable of long-duration heavy-duty operations has intensified. Water-hydraulic systems exhibit less viscosity variation with increasing depth than oil-based systems, offering better adaptability to deep-sea conditions. Using seawater as the driving medium inherently eliminates issues such as oil contamination by water, frequent maintenance limiting underwater operation time, and environmental pollution caused by oil leaks. This paper introduces a deep-sea manipulator directly driven by seawater from the deep-sea environment. To address the challenges of weak lubrication and high corrosion associated with water hydraulics, a reciprocating plunger seal was adopted, and a water-hydraulic actuator was developed. The installation positions of actuator hinges and maximum output force requirements were optimized using particle swarm optimization (PSO), effectively reducing the manipulator’s self-weight. Through kinematic and inverse kinematic analyses and joint performance tests, a six-degree-of-freedom water-hydraulic manipulator was designed with a maximum reach of 2.5 m, a lifting capacity of 5000 N, and end-effector positioning accuracy within 18 mm.

Peculiarities of the existence of a focus cyatocephalosis among wild and cultivated salmon fishes in the reservoirs of the Izhora upland of the Leningrad region

One of the conditions for maintaining fish health in aquaculture is to control and prevent the presence of disease agents in the water supply sources of fish farms. The main advantages of industrial aquaculture to prevent the spread of parasites can be considered the use of groundwater and pellet feed. The use of an underground water source completely eliminates the possibility of the spread of parasites. In the case of using river, lakes or pounds water the consumption of pellets feed by fish should exclude their eating of invertebrates — intermediate hosts of parasites with a complex life cycle. However, we have found singles Cyathocephalus truncatus (Pallas, 1781) cestodes in juvenile rainbow trout in industrial conditions. This served as the basis for research on the spread of this parasite both in natural reservoirs and fish farms of various types located within the Izhora upland. Cyathocephalus truncatus cestode is a dangerous parasite with a complex life cycle that is widespread mainly in salmon fish. The paper presents experimental data highlighting the impact of fish farming factors and nutritional selectivity on the spread of the parasite. Special attention was paid to the infestation of Salvelinus lepecheni grown in the FSGCR in order to replenish the natural population. As a result of our research conducted over three years, fish of this species have not been invaded by the parasite in both industrial and experimental conditions. This indicates the safety of juveniles reproduced in the FSGCR for settlement in natural reservoirs. In order to determine the boundaries of the natural focus of cyatocephalosis, 106 specimens of salmon fish from 8 reservoirs were tested for infection. Methods of preventing disease in flowing pools are proposed. It has been suggested that the preservation of the focus is ensured by the progenis of the cestode procercoids, excluding the need for a definitive host (fish) to maintain the helminth population in isolated hydraulic water sources.

Hydraulic permeation-induced water concentration gradients in ion exchange membranes

Although substantial literature has detailed transport through swollen membranes, there are still conflicting reports regarding the fundamental physics of hydraulic water transport in such materials, with a long-standing debate centered on the applicability of the pore-flow and solution-diffusion mechanisms. The critical thermodynamic distinction between these models is the presence of a membrane-phase concentration gradient. For pure solvent transport, the pore-flow model presumes that a membrane-phase pressure gradient drives transport in the absence of a concentration gradient. In contrast, the solution-diffusion model proposes that a membrane-phase concentration gradient drives transport and that there is a negligible pressure gradient through the membrane. To address this topic for ion exchange membranes, this study reports measurements of water concentration profiles in pressurized films of Nafion and a commercial membrane based on sulfonated poly (styrene-co-divinylbenzene). Several films were stacked together in a custom-built permeation cell, with the feed side pressurized to between 68.9 and 137.9 bar, and the permeate side held at atmospheric conditions. At steady state, the experiment was stopped, the films were separated, and the water content of each film was measured, revealing a water concentration gradient through the stack thickness that increased with increasing feed pressure. The experimental data were in good agreement with theoretical predictions based on Fick's law and polymer-solvent swelling theories (i.e., Flory-Huggins and Flory-Rehner). These results are consistent with the solution-diffusion model and cannot be explained by a pore-flow mechanism.

Physical Modeling of a Water Hydraulic Proportional Cartridge Valve for a Digital Twin in a Hydraulic Press Machine

Digital twins are an emerging technology that can be harnessed for the digitalization of the industry. Steel industry systems contain a large number of electro-hydraulic components as proportional valves. An input–output model for a water proportional cartridge valve was derived from physical modeling based on fluid mechanics, dynamics, and electrical principles. The valve is a two-stage valve with two two/two-way water proportional valves as the pilot stage and a marginally stable poppet-type cartridge valve as the main valve. To our knowledge, this is the first time that an input–output model was derived for a two-stage proportional cartridge valve with a marginally stable main valve. The orifice equation, which is based on Bernoulli principles, was approximated by a polynomial, which made the parameter estimation easier and modeling possible without measuring the pressure of the varying control volume, in contrast with previous studies of similar types of valves situated in the pilot stage part of the valve. This work complements previous studies of similar types of valves in two ways: (1) data were collected when the valve was operating in a closed loop and (2) data were collected when the valve was part of a press mill machine in a steel manufacturing plant. Model parameters were identified from data from these operating conditions. The parameters of the input–output model were estimated by convex optimization with physical constraints to overcome the problems caused by poor system excitation. For comparison, a simple linear model was derived and the least squares method was used for the parameter estimation. A thorough estimation of the parameters’ relative errors is presented. The model contains five parameters related to the design parameters of the valve. The modeled position output was in good agreement with experimental data for the training and test data. The model can be used for the real-time monitoring of the valve’s status by the model parameters. One of the model parameters varied linearly with the production cycles. Thus, the aging of the valve can be monitored.

Correlation Between Water Erosion and Hydraulics of Slope–Gully Systems According to Check Dam Siltation Depth

Correlation Between Water Erosion and Hydraulics of Slope–Gully Systems According to Check Dam Siltation Depth

The Most Likely Flooded Soil in Terengganu State During Historically Greatest Rainfall Intensity

Water infiltration in the soil is an essential topic for investigation because soil fully saturated with water forms standing water that leads to flooding on top of the soil. Soil investigation is vital for agricultural study due to the necessity to know soil carrying capacity in holding water, field capacity, and also the soil temperature for biological activities and chemical reactions. However, human urbanization and expansion into previously unexplored soil areas could lead to unnecessary environmental stress, such as floods. Floodwater forms when the rainfall intensity exceeds soil water infiltration. The flood event is crucial since it affects the human livelihood and facility damages. Therefore, a good understanding of soil hydraulic water infiltration helps better understanding the cause of flood occurrence. The current study examines the soil series in Terengganu state with its soil properties concerning the soil water characteristics curve, which indicates the soil's ability to absorb and allow water movement in the ground. The equation used was the improved Richards’ equation that can be applied to examine the standing water or floodwater impacts on water infiltration. Also, the unsaturated soil moisture movement conditions can be investigated. The simulation equation verifies with benchmark datasets that was solved on Richards’ equation using a different numerical method. The twelve-soil series of Terengganu state subjected to water infiltration study subjected to flooded conditions, by exposing the soil to the highest rainfall identified in the history of Kuala Terengganu from 1985 to early 2023. The results reveal Jambu, Rhu Tapai and Rudua soil series' water infiltration rate was greater than the rainfall intensity, whereas other soil series could not accommodate the rainfall intensity. Thus, other soil series areas will likely encounter flooded conditions when exposed to heavy rainfall, as has occurred in history.

Perbandingan Penggunaan 3 Jenis Pipa untuk Sistem Penyediaan Air (Kajian Kasus Kawasan Industri Terpadu Kabupaten Batang)

Batang Regency is one of the areas located on the north west coast of Central Java province. Batang Regency is located in a strategic position, this area is traversed by primary arterial roads that connect West Java and DKI Jakarta with cities in Central Java and East Java Provinces. Batang Regency is divided into 15 sub-districts consisting of 239 villages, 9 sub-districts, 936 hamlets, 3,680 neighborhood units (RT) and 1,009 community units (RW). The total area of Batang Regency is 78,864.16 Ha. The widest sub-district is Subah District, which is 83.52 Ha (10.59%), while the smallest is Warungasem District, which is 23.55 Ha (2.99%) of the total area of Batang Regency. The Central Government's program to encourage the sector to strengthen the industrial sector in Indonesia, namely one of the developments in the Batang industry. The Government provides supporting facilities in the development of the Batang Industrial area through APBN financing. The Batang Industrial Estate has around 4,300 hectares of land to develop, for the first phase it will develop a land area of 450 hectares. To support the supply of drinking water in this area, PERUMDA of Sendang Kamulyan Drinking Water, Batang Regency will supply drinking water which will take water from the raw water source of the Bangkangan spring at 100 liters/second and will be supplied to the Industrial Area at 80 l/s. For the analysis of the drinking water supply system in this industrial area, the Epanet 2.2 program will be used by comparing the hydraulic analysis of the use of HDPE, PVC and iron pipe types/materials, residual pressure and diameter as well as calculating the amount of investment based on the type of pipe material. The results of running Epanet 2.2 on HDPE, Iron and PVC pipes with remaining water pressure at the end of the pipe at the KITB Junction, the remaining pressure is more than 10 meters, meaning that the water has flowed with sufficient criteria in the service area. Based on the analysis taking into account efficiency, the selected pipe is HDPE with an investment value of Rp. 20,273,230,410. The recommendations given for SPAM KITB, can use HDPE pipes, apart from lower costs HDPE pipes have a better roughness coefficient than PVC pipes and iron pipes and can also minimize pipe leaks. Lessons from this study with Epanet Software can calculate water hydraulics in the piping system such as water velocity, the furthest remaining water pressure can be known quickly, can determine the type and specifications of pipes used for the study area and known cost efficiency based on the type of iron, PVC and HDPE pipes.

Design and experimental validation of a valve-distributed water radial piston pump

In underground coal mining, there is an urgent need for reducing the noise, hydraulic shock, and leakage of reciprocating pumps. Flow pulsation is strongly dependent on the number of pistons for single-acting reciprocating pumps. Water hydraulic radial piston pumps (RPPs) allow the pistons to be radially distributed, which makes the multi-piston design easier compared to traditional single-acting reciprocating piston pumps. In this study, a novel valve-distributed water RPP was developed in which the star wheel assembled on the camshaft is used to drive the connecting rod-crosshead-piston assembly and realize the reciprocation of the piston and suction-discharge of the pump check valves. Mathematical and numerical models representing the RPP were built using MATLAB and AMESim, respectively. Three-dimensional computational fluid dynamics analyses were performed to investigate the internal flow field of the suction and discharge circuits as well as the flow characteristics of the discharge valve opening. A prototype pump was manufactured and tested for 200 h and then disassembled to evaluate the wear condition. The tested instant flow rates were lower than those obtained from the theoretical and simulation analyses. The experimental results also revealed that the average flow rates were almost independent of the output pressure and that the volumetric efficiency decreased with increasing rotational speed when the output pressure was larger than 25 MPa. Inspecting the disassembled water RPP revealed that scuffing problems occurred in the pistons, whereas the other components remained intact. The findings of this study offer a reference for water hydraulic power units in various applications and for investigating the intensity of water hydraulics.

Experimental Investigation about the Effects of Blockage on Upstream Box Culverts

This experimental study focuses on scouring in box culvert inlets under steady-state conditions and at different percentages of blockage ranging from 0% to 65%, and also looks at the hydraulics of water in the culvert. The investigation shows that the blockage of the culverts has influenced the scouring pattern at the blocked culverts' entrances. Ten experiments were carried out at the laboratory to see how blockage impacts the scouring pattern upstream of a box culvert during steady flow. Both partially blocked and unblocked cases were implemented in this study. The experimental tests were done until the equilibrium scour occurred, which took about 3.5 hours of water flow to reach equilibrium conditions. The results revealed that the blockage will increase the water depth at the inlet by about 30%–50%, which may affect the safety of structures or cause culvert failure. In addition, the results discovered that the maximum scour depth, which inversely correlated with the obstruction upstream of the box culvert, increased with increasing discharge.

Numerical simulation of thermal hydraulics of supercritical pressure water with 2×2 rod assembly wrapped differently with a wire

Through the use of CFD, a thermal-hydraulic analysis was carried out on a set of 4 rod assemblies. The common wire-wrapped spacers on the fuel assemblies are wound in the same direction for all rods. Because of this design, it is anticipated that there would be an adverse flow in all of the sub-channels. In the course of this analysis, this flow was demonstrated to be real. In order to achieve desirable flow characteristics for coolant mixing, a novel configuration for wire-wrapped spacers is proposed here. This pattern designates a group of 4 rods, the rods have the wrapping system of clockwise and anticlockwise pattern. It was determined that this pattern had an exceptional mixing effect as well as a uniform flow. This pattern has a maximum temperature area that is approximately 8.5 °C lower than that of the conventional wire-wrapped fuel bundle arrangement. When compared to the regular pattern, the pressure drop caused by the new arrangement was approximately 1.9% less severe. The redesigned layout of the rod assembly improves heat transfer while also reducing the amount of pressure loss that occurs.

Deformation Characteristics of Three-Dimensional Spiral Soft Actuator Driven by Water Hydraulics for Underwater Manipulator.

The emergence of bionic soft robots has led to an increased demand for bionic soft actuating ends. In this study, a three-dimensional spiral water hydraulic soft actuator (3D-SWHSA), inspired by the winding action of an elephant's trunk, is proposed to provide a more targeted soft actuator catching method. The 3D-SWHSA is composed of multiple bending and twisting units (BATUs), which can produce winding deformation after being pressed. By using the principles of virtual work and integrating the Yeoh 3rd order model, a predictive model for winding was established to investigate the bending and twisting characteristics of BATUs with varying structural parameters through finite element simulation. Following the selection of an optimal set of structural parameters for the 3D-SWHSA, its bending and deformation capabilities were simulated using finite element analysis and subsequently validated experimentally. To validate its flexibility, adaptability, and biocompatibility, successful catching experiments were conducted in both air and underwater environments. Underwater organisms, including organisms with soft appearance such as starfish and sea cucumbers, and organisms with hard shell, such as sea snails and crabs, can also be caught harmlessly. In cases where a single 3D-SWHSA is insufficient for capturing objects with unstable centers of gravity or when the capture range is exceeded, the double 3D-SWHSAs can be utilized for cooperative winding. This study affirms the great potential of 3D-SWHSA in diverse marine applications, including but not limited to marine exploration, fishing, and operations.

Drought effects on water status, plant hydraulics and growth in Eucalyptus grandis and clonal hybrids with red gums and E. urophylla

Afforestation with Eucalyptus species occupies over a million hectares in Uruguay, and E. grandis is one of the most cultivated species, mainly for the timber industry. However, the increasing frequency of drought and heat waves in the region raises the need to evaluate hybrids with red gums (E. camaldulensis and E. tereticornis), since they are known to sustain gas exchange and growth even under severe drought conditions. Hybrids with E. urophylla are also evaluated for plantations in subtropical regions. This study aimed to compare the effects of drought on plant water status, hydraulics, and growth of E. grandis (one clone; G), E. grandis × camaldulensis (one clone; GC), E. grandis × tereticornis (one clone; GT), and E. grandis × urophylla (two clones; GU1 and GU2). Two drought-stress cycles were applied to six-month rooted cuttings from mid-spring to early fall under greenhouse environmental conditions. Predawn leaf water potential (?pd), midday leaf water potential (?md), relative leaf water content (RWC), stomatal conductance (gs), and plant growth were measured across each cycle. Daily fluctuation of Ψ was calculated as ΔΨ = Ψpd - Ψmd. Specific (kS) and leaf-specific (kL) hydraulic conductivities and specific leaf area (SLA) were measured at the end of the experiment. Percentage loss of hydraulic conductivity (PLC) was calculated after removing the xylem embolism. Preliminary results suggest that both red-gum hybrids had higher PLC under moderate-to-severe drought, as a consequence of maintaining high water potential gradients to sustain transpiration and carbon fixation throughout the experiment. Under the well-watered condition, no clonal difference was observed. Also, GT showed a three-fold increase in cavitation and had 1.5 times stomatal opening (gs) than the most drought-sensitive clone (E. grandis, G), and exhibited the lowest reduction (17%) in diameter growth under drought. Also, GC attained the highest height at the end of the study, 40% higher than E. grandis, and increased by 25% the SLA under drought. GU clones reached the highest diameter at the end of the study. Correlations among functional variables are explored, and the water supply capacity to the foliage among clones is discussed for a better understanding of drought resistance strategies and growth performance of the different taxa.

Polysulfone/sepiolite nanocomposites and disulfonated polysulfone as desalination membranes

This research targeted the preparation of new sepiolite-based nanocomposites and sulfonated polysulfone and compare them as desalination dense membranes. At the first step, a polysulfone with appropriate molecular weight was synthesized by condensation polymerization. The hydrophilic nature of the synthesized polymer was improved using two different methods: addition of various percentage (0.5–5% by weight) of sepiolite nanorods into the polymeric matrix, and introduction of sulfonated groups with 35–45 wt% sulfonation content to the polysulfone main chain. Precipitation by solvent evaporation was used to produce dense membranes after casting polymer solutions. FTIR, 1HNMR, and EDAX were used to identify the chemical structures of polysulfone, related nanocomposites, and sulfonated polysulfone. Also, the prepared samples were evaluated by equilibrium volume fraction of water, contact angle, water absorption, density, SEM, TGA, DSC, AFM and tensile test. Finally, the operation tests of the membrane including water flux, sodium chloride rejection, hydraulic water permeability, and salt permeability were investigated.

Leaf hydathode occurrence in indigenous New Zealand angiosperm trees: a preliminary survey

ABSTRACT Toothed leaf margins are common (∼36%) in the New Zealand indigenous flora, and are most abundant in cool forests with high rainfall. Toothed margins are often associated with hydathodes, specialised structures that release water and solutes to maintain positive xylem pressure. However, the presence of hydathodes is mainly known from herbaceous plants. Here we investigate the presence and morphology of hydathodes in indigenous woody species representing 25 families, 33 genera and 57 species, with toothed and entire leaf margins. We tested whether toothed leaf margins on predominantly evergreen species are associated with hydathodes. Two types of structures on leaves were recognised: laminar hydathodes, water pores larger than normal stomata and associated with veins, and hydathodes positioned at the terminus of leaf teeth serviced by principal veins. Laminar hydathodes occur more frequently, but not exclusively, on toothed leaves (on 61.8% of toothed species vs. 48.0% of entire-margined species). Leaf tooth hydathodes are complex structures with undifferentiated, porous tissue plugs linked to splayed vein termini of vessel elements and often form a distinctive cap on leaf teeth. Tooth hydathodes occur on ∼90% of the serrated leaves species sampled. Ontogenetic differences in hydathode occurrence were noted in Alectryon excelsus as leaf morphology changes with plant age from a serrated to a non-serrated form. Quintinia acutifolius showed a similar pattern between individuals with different leaf morphologies. In our sampled dataset, tree species with any type of hydathode occur in areas with a higher ratio of rainfall to potential evapotranspiration than tree species without hydathodes. This pattern was not observed in shrubs. The strong association between marginal hydathodes and toothed leaves in New Zealand trees, plus the association with higher rainfall environments, suggests that these structures function to release hydraulic water pressure in plants on periodically saturated soils in high rainfall zones.

EXPERIMENTAL STUDY OF A VARIABLE BUOYANCY SYSTEM FOR LOW DEPTH OPERATION

Autonomous Underwater Vehicles (AUVs) are used for the underwater survey both in coastal areas and deep sea without any human intervention during their operations. However, high energy consumptions required by the thrusters of the AUV’s adversely affect their performance such as range and endurance, etc. Herein, we have presented a novel design and development of a standalone variable buoyancy system for autonomous underwater vehicle and investigated the numerical and experimental analysis of Variable Buoyancy System (VBS) in standalone mode. Design idea is based upon the ‘Pump Driven Variable Buoyancy System (PDVBS)’ using ‘Water Hydraulic Variable Buoyancy System (WHVBS)’ method to control the buoyancy using a diaphragm type positive displacement pump (PDP) with capacity of the maximum buoyancy change rate of 4.5 kg/min. Detail experimental and simulation performance of the developed VBS has been investigated. Developed VBS is tested for maximum depth of 5 m and compared the performance of the experimental and simulation results. Presented results demonstrate that designed VBS is effective in changing buoyancy and controlling heave velocities and that will result to achieve the higher range and endurance and better performance in rescue/attack operations.

Seville history insight through their construction mortars

Seville is intimately linked to its historic role and extensive cultural heritage. The city has been occupied by Romans, Arabs and Christians, who built important historical buildings. Roman (first–second centuries) and Arabic (eleventh century) buildings, medieval Shipyard (thirteenth century), San Isidoro and Santa Maria de las Cuevas monasteries (fifteenth century), Santa María de las Cuevas (fifteenth century modified in eighteenth century), El Salvador Church (eighteenth century), the Royal Ordnance building (eighteenth century) and Santa Angela de la Cruz convent (twentieth century) performed with lining mortars, and mortars used in building stones (City Hall and Marchena Gate), all of them located in Seville (Spain), have been studied. Ninety-four mortar samples (employed as structural, plaster, coating) originally used or applied in restoration processes have been collected to perform an archaeometry study. The ratio of CO2 mass loss to hydraulic water (H2O) mass loss, and the mineralogical characterization by X-ray diffraction has been used to compare the mortars used in the different historical periods. Mainly hydraulic mortars were widely used in all these studied monuments as most mortars showed CO2/H2O ratios within the 4–10 range. Moreover, the thermal analysis curves also showed a broad temperature range for the thermal decomposition of the carbonate fraction of the mortars.

Flowback and early-time production modeling of unconventional gas wells using an improved semi-analytical method

Multiple fractured horizontal wells (MFHWs) currently are the only possible means of commercial production from the low and ultra-low permeability unconventional gas reservoirs. In early production time, flowback fluid, which constitutes of hydraulic water and gas flow within fractures, is collected and analyzed. Flowback analysis has been shown to be a useful tool to estimate key properties of the hydraulic fracture such as conductivity and pore volume. Until date, most tools of flowback analysis rely on empirical and approximate methods. This study presents an improved Green-function-based semi-analytical solution for performance analysis of horizontal gas wells during flowback and early production periods. The proposed solution is derived based on coupling the solutions of two domains: a rigorously derived Green’s function-based integral solution for single-phase gas flow in matrix, and a finite-difference, multiphase solution for gas–water two-phase flow in the fracture. The validity of proposed semi-analytical solution is verified by finely gridded numerical models built in a commercial simulator for a series of synthetic cases considering a variety of fluid and reservoir property combinations, as well as various different production constraints. Comparisons against available empirical and approximate methods are also provided for these cases.

Estimation of Drag Reduction by Polymer Additives at High Reynolds Numbers Using Rheological Measurements

In industrial applications such as hydraulic water fracking, polymers are added at dilute concentrations to the flow causing significant drag reduction (DR) and leading to a massive reduction to pump energy cost. In recent years, an alternative approach that is based on rotational flow has shown capabilities of measuring DR based purely on rheological testing. Nonetheless, there are some limiting assumptions in this approach that can lead to inaccurate interpretation of the data, especially for non-Newtonian polymer solutions, where the Reynolds number (Re) is evaluated at the infinite-shear or solvent viscosities. However, it is well known that the apparent viscosity of the polymer solutions is higher than that of a solvent at a stable region and lower than infinite shear viscosity at an unstable one. In this study, we propose a theoretical form of the DR expression that is based on the Re, which is estimated at the apparent local viscosity measure. The work establishes a promising approach for screening DR agents using rheological measurements. Moreover, the study presents new theoretical findings and analyses for estimating DR and extrapolating the results to high Re. Two polymer solutions of xanthan gum (XG) and partially hydrolyzed polyacrylamide (HPAM) in distilled water are tested at concentrations between 5 and 150 ppm using a concentric double-gap cylinder. The proposed approach is found to be more consistent with the theory of linear flow (i.e., flow loop), where the DR in the stable region is found to be identically zero. The transition from stable to unstable regions is also consistent with the existing linear flow theory. This enhances the role of rheological testing for DR measurements and DR agent screening, which provides a platform for the application of simple and cost-effective rheometry in the DR industry.

The Impact of Sediment–Water Ratio and Hydraulic Residence Time on the Release of Inorganic Nitrogen from Sediments in the Pearl River Delta

Black-odorous water bodies in the Pearl River Delta have been treated. However, the re-release of nitrogen (N)-containing compounds in sediment can cause a relapse of black-odorous water bodies. Sediment–water ratio (SWR) and hydraulic residence time (HRT) influence pollutant release. Therefore, how to control SWR and HRT during the treatment process has become an urgent problem. This study focuses on the dynamic release of endogenous inorganic N from sediments into overlying water in a river channel of Dongguan City, Guangdong Province. Physicochemical parameters (dissolved inorganic nitrogen (DIN), NH4+-N, NO3−-N, NO2−-N, dissolved oxygen (DO), pH, oxidation-reduction potential (ORP), chemical oxygen demand (COD), Fe and total phosphorus (TP)) of overlying water were monitored under different SWRs (0.71, 0.38, and 0.16) and HRTs (13 days and 6.5 days), and the nitrogen release flux under different conditions was compared. Finally, the correlation and influence pathways among environmental factors were analyzed. The results showed that SWR significantly affected DO, pH, ORP, and sediment N release fluxes while prolonging HRT-promoted denitrification. DIN → NO2−-N → DO pathway had a total effect of 19.6%, and DIN may promote low DO concentration via NO2− oxidation. Maintaining reasonable SWR and HRT can reduce the release of inorganic N from sediment into the overlying water. This study provides a theoretical basis for controlling black-odorous water bodies.

Development of an Anthropomorphic Soft Manipulator with Rigid-Flexible Coupling for Underwater Adaptive Grasping.

Inspired by human hands and wrists, an anthropomorphic soft manipulator (ASM) driven by water hydraulics is proposed for underwater operations and exploration. Compared with traditional rigid manipulator, ASM has highly evolved grasping ability with better flexibility and adaptability, while it has better load capacity, grasping ability, and flexibility in comparison with the pneumatic gripper. ASM wrist is composed of rigid-flexible coupling structure with three bellows and a spindle, which generates continuous wrist pitching. The linear elongate characteristics of bellows and pitching performance of ASM wrist are simulated by finite element modeling (FEM) method and tested experimentally. The mathematical model of bending deformation for the water hydraulic soft gripper (WHSG) is established. The bending deformation and contact force of WHSG are simulated by FEM and measured experimentally. The ASM prototype is fabricated, and the grasping experiments in the air and underwater are conducted. It is confirmed that the developed ASM can switch between standard and expanded grasping position to adopt and grasp objects of different shapes and dimensions. And living animals with rough or smooth surfaces such as turtle and carp can also be caught harmlessly. ASM also exhibits preferable adaptability when the objects are out of grasping range or deviating from the grasping center. This study confirms that the developed ASM has enormous application potentials and broader prospects in the field of underwater operation, underwater fishing, underwater sampling, etc.