Water Flow Velocity Research Articles

Numerical and experimental investigation of an Archimedes screw turbine for open channel water flow application

AbstractLow‐head turbines are becoming an agricultural imperative due to their high efficiency, low cost, ability to operate at low flow rates and minimal environmental impact. Therefore, the Archimedes screw turbine (AST) can play a leading role for producing electric power, especially in Pakistan's rural areas where most of the places have less than 1 m head. In this research work, performance evaluation of AST was carried out at different flow velocities in terms of power coefficient and torque generated. Design parameters such as blade width, blade pitches, and blade rotational angles are also used for performance evaluation. For this purpose, computational fluid dynamic (CFD) analyses of AST blades were conducted at different water flow velocities (e.g., 1, 1.5, 2, 2.5, 3, and 3.5 m/s). ANSYS FLUENT was used for AST blade simulations using three different design parameters such as blade width, blade pitch, and blade rotational angles. Additionally, CFD simulations have inherent errors and uncertainties that may lead to findings and deviations from their exact or real values. To prevent these uncertainties and errors, an experimental study was also conducted to provide validation for the CFD simulation results. The results revealed from CFD simulations for optimized design parameters were then compared with experimental data. From the results, it was examined that the numerical findings were in good agreement with the experiment data. The highest power coefficient and power output values were obtained under optimized design parameters such as inner and outer diameter, blade pitch, blade width, blade rotation angles and shaft length (e.g., 40 mm, 120 mm, 130 mm, 2 mm, 60°, and 850 mm respectively). The findings can be useful to implement the AST unit for those places where the available water head is ranging from 1 to 6.5 m and a flow rate of 0.2–6.5 m3/s, especially for rural areas of Pakistan.

Analysis of layered boulders on asteroid (101955) Bennu and their implications for fluid flow on the parent body

AbstractThe observation of carbonate veins on asteroid Bennu supports the idea that large‐scale water flow may have occurred in carbonaceous asteroids in the early solar system. We identified and analyzed 11 boulders with layered structures on asteroid Bennu's surface using high‐resolution (centimeter‐scale) image and altimetry data obtained by the OSIRIS‐REx mission. The boulders' linear layer boundaries and parallel bedding follow the principle of original horizontality and suggest that they formed from sediment deposition by fluid flow on Bennu's parent body. We developed a simple model of the parent body (100‐km diameter with the density of CM chondrite material) and found that the water flow velocity had to be at least 21.1 cm s−1 to transport the largest clast observed embedded in a layered rock, which is 85 cm in average length. The flow velocity could have been as high as 26.5 cm s−1 if a larger clast observed on top of a layered rock was once embedded therein. Our results strongly support open‐system aqueous alteration on carbonaceous chondrite parent bodies.

The influence of locks on zooplankton in canals (the Bydgoszcz Canal and the Noteć Canal, Poland)

Artificial waterways are characterized by dams and locks that slow water flow. Such conditions can influence the environment of freshwater organisms, including the zooplankton community. Our research aimed to assess the impact of environmental and hydrological conditions on the zooplankton of sites upstream and downstream of canal locks. The study was carried out in 2021 and 2022. Water samples were collected monthly from two canals during the growing season. We evaluated how water flow velocity and selected environmental parameters (i.e., water temperature, Secchi disk visibility, conductivity, oxygen concentration, saturation, pH and chl-a concentrations) influence the zooplankton diversity (T) density (N) and biomass (B). Our study showed that the zooplankton of the canals was highly diverse. Rotifers dominated over crustaceans in diversity and density at all sites of canals. The statistical analysis revealed differences in environmental and biological conditions between habitats located upstream and downstream of locks. Rotifers density and biomass changed approximately proportionally to changes in chlorophyll at sites upstream of locks. It supports the hypothesis that rotifer communities are defined by the bottom-up effect linked to food supply (phytoplankton). The growth of crustaceans (density and biomass), as well as total zooplankton biomass, was affected by water temperature at sites downstream of the lock.

AN INTERACTIVE EVACUATION TOOL TO IMPROVE THE PUBLIC FLOOD PERCEPTION

Abstract. The advancing climate change increases the danger of heavy rainfall events and devastating floods, which significantly threaten people’s lives and properties. Geographic information system (GIS) has been a valuable tool for mapping flood risks and emergency management worldwide. In this paper, we develop an interactive evacuation tool to improve public flood perception. This work presents how to create an interactive and animated evacuation tool to strengthen the population’s preparedness and action ability in case of a flood. We simulate water depths and flow velocities for a flood scenario in Bonn, Germany. Afterwards, we investigate the flood’s impact on buildings and streets for different flood situations using geoinformation tools in the software QGIS. Based on thresholds from the literature, we identify endangered buildings where inhabitants have to evacuate and streets still ensuring safe locomotion options during the advancing flood. Taking possible shelter points for the population into account then allows for computing the shortest path to the nearest shelter at each flood situation. Our findings are summarized in evacuation maps that can be used together as interactive information tools for the public and can also serve rescue management and disaster education.

Three-dimensional X-ray imaging of macropore flow

Macropores are known to be important pathways for the rapid transport of water, solutes and colloids in soil. Nevertheless, we still know very little about how the topology and geometry of macropore networks govern water flow configurations and velocities in natural soil. In this study, we aimed at gaining more insight into macropore flow by using X-ray tomography to quantify air–water distributions in the macropore networks of undisturbed topsoil and subsoil columns of a clay soil at varying steady-state flow rates. We observed that while large fractions of the macropore network remained air-filled, the air phase only became entrapped when the irrigation rate was very close to the saturated hydraulic conductivity of the soil. The data enabled us to parameterize a kinematic wave model for water flow following the approach proposed in Jarvis et al. (2017a). Follow-up experiments would be required to evaluate whether these kinematic wave parameters derived by X-ray imaging match with those obtained from outflow measurements. We found that quantitative X-ray imaging of macropore flow through soils still remains a challenging task. We recommend that future experiments are conducted on smaller soil samples to improve image resolution and minimize experimental time spans as well as X-ray image noise and illumination bias. Such experiments could also include 3-D tracer imaging to identify the imaged macropore networks transporting most of the water (i.e. the backbone) at varying steady irrigation rates.

Modified geomorphic flood index (GFI) method on backwater problem in tidal tropical river for rapid flood assessment

The Geomorphic Flood Index (GFI) model can show flood inundation in a watershed based on flood events. Flood inundation can occur because of the backwater effect in the river channel. The different water levels from the river and tide that occur downstream may temporarily disturb the water depth and flow velocity. Because of this disturbance, a backwater effect might occur. The case study is located at the Plumbon River in Semarang City, which has the potential for a backwater effect in the river downstream. Backwater is a hydraulic phenomenon that occurs in rivers and can be simulated using a hydrodynamic model, as it can show the relationship between river discharge and tides. The conventional GFI method does not consider hydraulic effects, such as backwater effects, as part of the calculation. Therefore, modifications will be inserted into the calculation of the hydraulic effect on the modelling of flood inundation. The main purpose of this study is to build a modified GFI method that includes backwater analysis in its modelling to predict the backwater effect that occurs downstream of rivers and its impact on inundation. This study will help rapidly predict flood inundation.

Analysis of the hydraulic interference between the baffles and the composite hydraulic structure

The purpose of the present study is to examine the influence of baffles presence at downstream system on weir gate hydraulic response. Two baffles configuration (triangle and angle shapes) are installed in bed flume. Two different spacing are used between the baffles and two different directions for baffles are also adopted. The study tries to investigate the variation in upstream Froude number, downstream Froude number, Reynolds number, actual discharge, discharge coefficient, downstream average water depth and the hydraulic system efficiency which is expressed as function of downstream water depth. It has been shown that the number of baffles has a direct and significant impact on flow hydraulic characteristics of weir-gate structure regardless of the spacing between baffles and the direction of baffles related to flow. Baffles number and spacing have essential impact on the water flow velocity of system and this impact leads to increase the flow resistance. The results clarify that the upstream Froude number, downstream Froude number, Reynolds number, actual discharge and discharge coefficient are decreased with the increase in baffles number except the average downstream water depth which increases with increase in baffles number. The efficiency of hydraulic system gives a good indicator for using baffles with weir-gate structure. At the end this paper shows a fruitful result of efficiency. This experiment run condense on the baffle’s numbers and directions with respect to the water flow direction at the downstream regime. So, the rises in the water level relies on the numbers and directions of the baffles as compare to the case without using baffles at the flume downstream region. The actual discharge and weir-gate discharge coefficient are more sensitive to the increase in the baffles’ numbers and the baffles direction with respect to the water flow direction

Anti-scour performance of fluidized solidified slurry in dynamic water for scour repair

A novel method using fluidized solidified slurry for scour repair and protection around offshore foundation has been proposed recently. After being pumped to seabed area around foundation for scour protection or into the developed scour holes for scour repair, the fluidized solidified slurry is kept around the foundation for solidification which is still at a vulnerable state experiencing erosion and scour in the dynamic ocean water environment. Moreover, a reliable evaluation of loss of fluidized solidified slurry in scour repair or protection design using the new method requires to consider both the loss in pumping operation and solidification. Therefore, anti-scour performance of fluidized solidified slurry during solidification process is key for the novel technology. The current work conducted a series of experimental tests using a self-designed specially-targeted flume testing device to study the effects of flow property of fluidized solidified slurry and flow velocity of dynamic water on the anti-scour performance of solidified slurry in solidification under current. The retention rate of solidified slurry and scouring state were evaluated and discussed. Results indicates that the flow value that describing the pumpability of fluidized solidified slurry, is a key factor which affecting the critical starting velocity that characterizing the critical state of incipient motion. The critical starting velocity decreases with the flow value of fluidized solidified slurry. When the water flow velocity of current is larger than the critical starting velocity, the loss of fluidized solidified slurry is great, which can be evaluated by the retention rate. Empirical formulas for calculating the critical starting velocity and retention rate of fluidized solidified slurry in solidification was then proposed for the performance evaluation of fluidized solidified slurry application under current.

Computational hydraulics and hazard assessment of flooding on underground staircases

Underground flooding is intensifying due to urban expansion and more frequent extreme precipitation. Staircases are crucial for accessing underground spaces and evacuation during floods and it is of both academic and practical value to investigate how floodwater and the induced hazard evolve over underground staircases. This study examines flood dynamics on underground staircases and its relationship with staircase characteristics through a series of numerical experiments using a two-dimensional (2D) hydrodynamic model. The study also uncovers how staircase design influences flood hazard levels. Results indicate that shorter or higher steps lead to shallower water depths but higher flow velocities. The branch staircase experiences smaller water depths and flow velocities than the main one. The presence of staircase transforms a subcritical flow into a supercritical flow. Except in extremely deep floodwaters, pedestrians are more vulnerable to sliding than toppling on staircases. The stability of the human body is greater on steps with longer length and lower height (26.56°) or the branch line of the junction type. The relative stability of the human body is not necessarily a guarantee of complete safety and must be analyzed in conjunction with the comprehensive safety factor.

Development of High-Precision Urban Flood-Monitoring Technology for Sustainable Smart Cities.

Owing to rapid climate change, large-scale floods have occurred yearly in cities worldwide, causing serious damage. We propose a real-time urban flood-monitoring technology as an urban disaster prevention technology for sustainable and secure smart cities. Our method takes advantage of the characteristic that water flow is regularly detected at a certain distance with a constant Doppler velocity within the radar observation area. Therefore, a pure flow energy detection algorithm in this technology can accurately and immediately detect water flow due to flooding by effectively removing dynamic obstacles such as cars, people, and animals that cause changes in observation distance, and static obstacles that do not cause Doppler velocities. Specifically, in this method, the pure flow energy is detected by generating a two-dimensional range-Doppler relation map using 1 s periodic radar observation data and performing statistical analysis on the energy detected on the successive maps. Experiments to verify the proposed technology are conducted indoors and in real river basins. As a result of conducting experiments in a narrow indoor space that could be considered an urban underpass or underground facility, it was found that this method can detect flooding situations with centimeter-level accuracy by measuring water level and flow velocity in real time from the time of flood occurrence. And the experimental results in various river environments showed that our technology could accurately detect changes in distance and flow speed from the river surface. We also confirmed that this method could effectively eliminate moving obstacles within the observation range and detect only pure flow energy. Finally, we expect that our method will be able to build a high-density urban flood-monitoring network and a high-precision digital flood twin.

Progressive Dam-Failure Assessment by Smooth Particle Hydrodynamics (SPH) Method

The dam-break water flow is a complex fluid motion, showing strong nonlinearity and stochasticity. In order to better study the characteristics of the dam burst flood, the smooth particle hydrodynamics (SPH) method was chosen to establish a two-dimensional classical dam-burst model, and the flow velocity distribution graph was obtained by calculation and compared with the experimental results in the literature, and the fitting degree of the two was obtained to be 88.4%, which verifies the validity of the model. On this basis, according to the principle of dam failure, the two failure modes of equal-interval gradual failure and progressive gradual failure were simulated, and the water body characteristics such as water flow velocity, energy, pressure, etc., were analyzed based on the different working conditions of the two modes to obtain the characteristics of gradual dam-failure water flow under the two kinds of numerical models. The simulation results show that, compared with the instantaneous dam failure mode, (1) the flow rate of the dam-failure stream reaching the downstream slows down in the gradual dam-failure mode; (2) the depth development of the breach extends downward in layers and stages over time, and the overall duration of the breach is prolonged; (3) the destructive power of the dam-failure flood is weakened as the number of segments increases. The results of the study show that, compared with the instant dam-failure mode, the calculation results of the breach development considering the progressive gradual dam-failure mode are more in line with the theoretical solution and closer to the actual process of dam failure, which can provide ideas and references for advancing the numerical study of dam failure.

Design of Micro Hydrokinetic Energy Harvester of Marine Animal Movement for Underwater Monitoring

The underwater mobile monitoring platform that utilizes marine animals as carriers provides a new solution to address the issues of short endurance, high costs, and bulky size associated with traditional underwater mobile monitoring platforms. Based on most marine animals that have the behavioral habit of long‐duration swimming, a micro hydrokinetic energy harvesting system is proposed. This system applies a miniature vertical‐axis water turbine as its energy conversion component. The hydrokinetic energy is derived from the relative movement between marine animals and the surrounding seawater. A conceptual design of a novel underwater mobile monitoring platform is presented. A finite element model of the external‐rotor permanent magnet synchronous generator is established to comprehensively evaluate the performance of the generator. Numerical simulation is utilized to conduct a comparative analysis of different diversion channel designs. Preliminary water tank experiments show that the designed micro energy harvester can effectively capture the hydrokinetic energy generated by water flow movement. The startup flow rate of the harvester is around 0.16 m s−1. The output power increases with the increase in water flow velocity, reaching a maximum value of ≈57 mW within the range of water flow rate of about 0.2–0.5 m s−1.

Influence of fluorine incorporation into waterborne acrylic coatings on resulting hydrophobic, thermal stability and drag- reduction properties

Fluorinated polyacrylate copolymers containing various amounts of 1H,1H,2H,2H-perfluorooctyl methacrylate (FA) were synthesized via a miniemulsion polymerization process. The characteristics of latex particles and films were investigated using transmission electron microscopy, dynamic light scattering, attenuated total reflectance Fourier transform infrared spectroscopy, 1H and 19F nuclear magnetic resonance spectroscopy, atomic force microscopy, energy dispersive spectroscopy, water contact angle measurements, and thermogravimetric analysis. The results showed that particle size increased almost linearly with FA content, and the surface hydrophobicity of the films increased with FA content up to 14.6 wt% and then plateaued. As the FA content increased, the surface roughness of the films initially increased and then decreased. The thermal stability of fluorinated polyacrylate was significantly enhanced when a high amount of FA was incorporated into the polymer chains. The fluorinated acrylic copolymer coating also exhibited a significant drag reduction effect, with the maximum drag reduction ratio reaching 12% at a water flow velocity of 0.8 m/s.

Numerical Simulation Study on the Distribution Characteristics of Precipitation Seepage Field in Water-Rich Ultra-Thick Sand and Gravel Layer

The distribution characteristics of a seepage field generated by precipitation affects the deformation damage of the geological body and engineering geological stability, especially a seepage field with a water-rich ultra-thick sand and gravel layer. In order to study the seepage field distribution characteristics of a water-rich ultra-thick sand and gravel layer, taking Luoyang Metro Line 1 as the engineering background, combined with the actual monitoring data of on-site precipitation, numerical simulation was used to study the seepage characteristics of the pit project precipitation with a suspended water-stop curtain. Through the study, the distribution characteristics of the seepage field under different precipitation depths and aquifer thicknesses were obtained, and the changes in pore water pressure characteristics, flow velocity and water inflow, depending on the precipitation depth and aquifer thickness, were analyzed. The research results show that, when comparing the calculated and measured results of the water level drop in the foundation pit, the average value of the error of the water level drop value in the pit and the descending well is 11.7%, which indicates that the calculation model meets the needs for its use in calculation and analysis. Under the conditions of a suspended water-stop curtain and precipitation, for the pore water pressure characteristics, the variation amplitude of the pore water pressure inside the pit increases with the precipitation depth and aquifer thickness. For the maximum flow velocity, all characteristics are present at the bottom of the suspended water-stop curtain, near the inside of the pit. The maximum flow velocity increases linearly with the precipitation depth and there is a threshold when the aquifer thickness is five times the precipitation depth. For water inflow, it increases with the increase in the precipitation depth and aquifer thickness, but, with a continuous increase in the aquifer thickness, the magnitude of water inflow growth decreases.

A SINS/DVL navigation method based on hierarchical water velocity estimation*

Aiming at the problem that Doppler velocity log (DVL) cannot measure the velocity of the vehicle in the middle water environment, a Strap-down Inertial Navigation System (SINS)/DVL integrated navigation method based on hierarchical water velocity assistance is proposed. Firstly, according to the principle of DVL water layer flow measurement, the paper gives a hierarchical water recurrence principle. On this basis, a water velocity estimation method based on average weighted recurrence is proposed. The carrier depth information is introduced in this method, and the carrier velocity information is obtained by means of average value. This method can prevent the carrier velocity anomaly caused by the large error of single-layer water velocity measurement. Secondly, in view of the problem that the DVL water velocity measurement is easily disturbed in the middle water environment, a sliding window and a Chebyshev polynomial fitting function are introduced to realize the robust treatment of the water velocity. On this basis, combined with the Huber M robust filter algorithm, a hierarchical water velocity assisted integrated navigation algorithm based on the improved Huber M robust estimation is proposed to further improve the autonomous navigation accuracy in the middle water environment. Finally, the method proposed in this paper is verified by simulation. The results show that the hierarchical water velocity estimation method proposed in this paper can effectively estimate the water flow velocity, and its robust filtering algorithm can further improve the SINS/DVL integrated navigation accuracy in the middle water environment.

Habitat suitability of Unionidae host fish in the Rhine Delta

Unionid populations are declining worldwide as they are threatened by anthropogenic habitat alterations, the introduction of invasive alien species and the effects of climate change. Several studies have focused on the habitat preferences of adult mussels but none to date have reported on the importance of the habitat preferences of host fish species. The aim of this study was to determine the habitat preferences of unionid host fish species in the Netherlands, to examine potential differences between native and alien host fish species, and to evaluate the effect of alien host fish species on unionid dispersal. Species sensitivity distributions (SSDs) were constructed for the range of occurrences and laboratory tolerance of host fish species in the Netherlands for water temperature, substrate type, flow velocity, and water depth. A case study was selected to assess the suitability to substrate type, flow velocity and water depth of a novel river habitat along longitudinal training dams in the river Waal. Unionid host fish species in the Netherlands preferred shallow littoral zones (0.1 m) with low flow velocity (0.05 m/s), an average water temperature of the Rhine delta (15°C), and most substrate types (ranging from silt to cobbles). Boulder substrate was the most limiting factor of the abiotic factors assessed for both native and alien host fish species. Management options for unionid populations should include host fish species in their assessments while focusing on creating and maintaining areas with limited boulders and implementing alien host fish species removal measures.

Real-time tsunami forecasting system with nonlinear effects using Green’s functions: application to near-shore tsunami behavior in complex bay topography

ABSTRACT In this study, a real-time tsunami estimation method was developed using the linear superposition of Green’s functions, which account for nonlinear tsunami effects around coastal areas. To this end, first, the nonlinear effects associated with the inundation and bottom friction and advection terms in a nonlinear long-wave model were investigated, focusing on large tsunamis around Urado Bay in Kochi Prefecture, Japan, which is at risk of future damage from tsunamis produced by the Nankai Trough earthquake. The results indicate that the effects of advection play a more significant role than those of the inundation and bottom friction in terms of accurately estimating near-shore tsunami propagation. Then, based on these results, Green’s functions were modified to account for the linearly approximated effects of the advection terms. By applying the developed method to tsunamis around Urado Bay, it was demonstrated that accurate estimations of the water surface level and flow velocity changes could be quickly obtained at any location around the bay. The developed method can be applied to real-time tsunami inundation forecasting and off-shore evacuation simulations of vessels to support optimal evacuation decisions.

In-situ experimental study on heat exchange capacity of long-span energy tunnel exchangers

Energy tunnel is a new type of geothermal exchanger in ground source heat pump systems due to their technical and cost improvements over traditional borehole geothermal exchangers. The main reason that the factors affecting the heat exchange capacity of energy tunnel are unclear makes its development be restricted. An in-situ full-scale study using the thermal response tests (TRT) and thermal performance tests (TPT) is performed to investigate the factors affecting the heat exchange capacity in Badaling Energy Tunnel of Beijing-Zhangjiakou High-speed Railway. This paper analyzes the influences of constant heating power, inlet water temperature, air temperature in tunnel, circulating water flow velocity, operation mode, and pipe connection on the heat exchange capacity of the energy tunnel. The test results reveal that (1) the heat exchange rate of the energy tunnel decreases with the increasing constant heating power, (2) the heat exchange rate of the energy tunnel is positively proportional to the inlet water temperature, (3) the heat exchange rate of the energy tunnel at a circulating water flow velocity of 1.1 m3/h is larger than that at 0.5 m3/h, it is smaller than that at 0.8 m3/h, (4) the air temperature in tunnel has a great effect on the heat exchange rate of the energy tunnel, and the pipes connected in parallel or connected in series have a slight effect on the heat exchange rate of the energy tunnel, (5) the average heat exchange rate in an intermittent operation mode is approximately 18.5% larger than that in a continuous operation mode. The test results can be used for the thermal design of energy tunnels.

Heat pump efficiency with energy geostructure: Numerical long term modelling

Heat pump efficiency with energy geostructure: Numerical long term modelling

Management Techniques of Ancestral Hydraulic Systems, Nasca, Peru; Marrakech, Morocco; and Tabriz, Iran in Different Civilizations with Arid Climates

The research aims to evaluate various management techniques of Ancient Hydraulic Systems (AHS) in different civilizations in arid climates, in cities located in Nasca in Perú (Puquio), Marrakech in Marruecos (Khettara) andTabriz in Irán (Qanat). The scarcity of water resources in these areas compelled the inhabitants to seek water management solutions to meet the necessary water supply for the population at the time. The methodology employed was a case study in which climatic data, supply, and operation of AHS were analyzed. The different indicators studied resulted in findings that, in the case of Nasca, the system relied on lintels, utilizing robust materials such as stone. They employed geometry to control water flow velocity, inclined walls to prevent collapses, and terraces to facilitate access to underground galleries. In the cases of Tabriz and Marrakech, their systems were based on excavations and reinforcements primarily using clay and earth as materials. In conclusion, the techniques employed in different civilizations are responses to contextual realities, offering an adaptive solution to environmental and physical challenges with a sustainable focus within their immediate surroundings.