Unidirectional Water Flow Research Articles

Controlled Chemical‐Patterning of Textile to Accelerate Anti‐Gravity Water Flow

AbstractBio‐inspired unidirectional flow of tiny aqueous droplets across the fibrous substrate paved the way for the emergence of various advanced materials. In the past, textiles decorated with noncontact‐based wettability‐patterns enabled unidirectional water flow—without flooding the top surface by the transferred water. However, such approaches mostly suffer from a low (≈0.176 µL mm−2 s−1) flow rate and are likely to delay the overall liquid ejection process. Here, a chemically reactive coating capable of tailoring water wettability (121.3° ± 2.4° to 153.3° ± 1.8°) is introduced on commercially available textiles to develop chemically modulated wettability‐pattern for achieving a rapid (2.57 ± 0.28 µL mm−2 s−1) flow rate of water against the gravity with an ability to roll the accumulated liquids on the top surface. The spatially selected and controlled chemical modification with hydrophilic and hydrophobic small molecules through a 1, 4‐conjugate addition reaction yielded a 3D channel with a customized wettability gradient. The pinning and depinning of invaded water through such chemically decorated channels enabled unidirectional and fast penetration of liquid, where the water penetration resistance largely depends on the water penetration direction and dimension of the chemically modulated channels.

Analysis of the interaction between surface water and groundwater using gaseous tracers in a dynamic test at a riverbank filtration intake

AbstractWe discuss a study designed to elucidate the genesis and inflow conditions at riverbank filtration wells located on a mountain river. This article seeks to identify the most important drivers of spatio‐temporal dynamics of water flow in the hyporheic exchange zone, in natural conditions and conditions disturbed by the water abstraction. In our study we try to contribute to further understanding the dynamics of groundwater mixing with river water in the hyporheic exchange zone. We focus on understanding river/aquifer interactions at the scale of reach of an intake, especially the unidirectional water flows induced by water abstraction. To understand these issues, a two‐day field hydrogeological experiment was conducted based on a pumping test of increasing intensity. At each pumping stage, groundwater and river samples were collected to determine the concentration of noble gases, CFCs, SF6, stable isotope content, and the chemical composition of the water. The study results indicate a short pressure propagation time (of the order of several hours) between the intake and the river, which already results in the inflow of water from the river–aquifer mixing zone at low rates of water abstraction by the intake. As pumping rates increase, the conditions of mixing and inflow of water to individual wells stabilize or approach stabilized conditions in less than 1–2 days. The share of river water in the water flux flowing into the intake does not exceed 12%, whereas the ratio of river water to groundwater in the mixing zone is estimated at 1 to 7 or more. The range of the river‐aquifer mixing zone may reach up to 170 m from the river and this range can be identified with a good approximation as coinciding with the range of the zone of hyporheic exchange in the study area.

Wetting hysteresis induces effective unidirectional water transport through a fluctuating nanochannel.

We propose a water pump that actively transports water molecules through nanochannels. Spatially asymmetric noise fluctuations imposed on the channel radius cause unidirectional water flow without osmotic pressure, which can be attributed to hysteresis in the cyclic transition between the wetting/drying states. We show that the water transport depends on fluctuations, such as white, Brownian, and pink noises. Because of the high-frequency components in white noise, fast switching of open and closed states inhibits channel wetting. Conversely, pink and Brownian noises generate high-pass filtered net flow. Brownian fluctuation leads to a faster water transport rate, whereas pink noise has a higher capability to overcome pressure differences in the opposite direction. A trade-off relationship exists between the resonant frequency of the fluctuation and the flow amplification. The proposed pump can be considered as an analogy for the reversed Carnot cycle, which is the upper limit of the energy conversion efficiency.

Local-scale feedbacks influencing cold-water coral growth and subsequent reef formation

Despite cold-water coral (CWC) reefs being considered biodiversity hotspots, very little is known about the main processes driving their morphological development. Indeed, there is a considerable knowledge gap in quantitative experimental studies that help understand the interaction between reef morphology, near-bed hydrodynamics, coral growth, and (food) particle transport processes. In the present study, we performed a 2-month long flume experiment in which living coral nubbins were placed on a reef patch to determine the effect of a unidirectional flow on the growth and physiological condition of Lophelia pertusa. Measurements revealed how the presence of coral framework increased current speed and turbulence above the frontal part of the reef patch, while conditions immediately behind it were characterised by an almost stagnant flow and reduced turbulence. Owing to the higher current speeds that likely promoted a higher food encounter rate and intake of ions involved in the calcification process, the coral nubbins located on the upstream part of the reef presented a significantly enhanced average growth and a lower expression of stress-related enzymes than the downstream ones. Yet, further experiments would be needed to fully quantify how the variations in water hydrodynamics modify particle encounter and ion intake rates by coral nubbins located in different parts of a reef, and how such discrepancies may ultimately affect coral growth. Nonetheless, the results acquired here denote that a reef influenced by a unidirectional water flow would grow into the current: a pattern of reef development that coincides with that of actual coral reefs located in similar water flow settings. Ultimately, the results of this study suggest that at the local scale coral reef morphology has a direct effect on coral growth thus, indicating that the spatial patterns of living CWC colonies in reef patches are the result of spatial self-organisation.

Electropumping of water in nanochannels using non-uniform electric fields

Pumping fluids at the nanoscale is of fundamental importance to nanofluidic systems. We perform molecular dynamics simulations and provide the extended Navier-Stokes (ENS) equation to prove the electropumping possibility of using non-uniform electric fields to induce the continuous and unidirectional net flow of water confined in nanochannels. The net flow can be seen as a result of the combined effects of the unidirectional orientation of water molecules and the net force induced by the electric field intensity difference between O and H atoms in a water molecule. Higher net flow rates can be achieved by enhancing the electric field intensity gradients through the characteristics parameter adjustment of external electric fields. Importantly, the electropumping is more effective than the pressure-driven flow due to the ordered arrangements of water molecules in electric fields. The ENS equation proposed is more applicable at the flow field with high order degree of water molecules.

Plastic Filtration and Decomposition According to Ricochet Filtering Mechanism Using Ideonella sakaiensis

Our oceans have been under immense stress due to the deposition and accumulation of marine debris, of which 80% are plastics. Of these, microplastics which are small plastic fragments measuring less than five mm, have been a real bane to the marine fauna, especially the ornamental fishes inhabiting coral reef regions. The multibillion-dollar marine ornamental fish trade depends on these fishes caught from coral reefs. It has often been found that these small fishes are severely affected due to the choking of their gills with microplastics as they are natural filter feeders. To curb the load of plastics in the oceans, and especially in the waters around coral reefs, this study aims to develop a small-scale solution, which could later be scaled up by increasing the size and number of each unit as required. The system has been inspired by the filter-feeding mechanism of manta rays as a basic model for the filtration module. The use of a bacteria named Ideonella sakaiensis, which has been known to decompose plastics inherently is the second level of ideation that has gone into the design. The whole system has been envisaged as a floating system, where the filtration units would be submerged under water and the design of the platform over water would have a provision for self-sustenance, apart from the obvious role in maintaining buoyancy. Each filtration unit has been designed to possess multiple layers of sieving, vortexing and cross-flow filtration with a batch of I. sakaiensis at the end of the unit. To maintain a unidirectional flow of water, a fan would be placed at the end of these filtration units. This system can be a solution to the accumulation of plastics in a localized environment and can be scaled up in terms of size and the number of units to cover a greater area and volume to reduce the menace of plastic pollution. This could be a unique and cost-effective answer to the loss of marine fauna, more specifically ornamental fishes to the curse of microplastics.

A near-natural experiment on factors influencing larval drift in Salamandra salamandra

The larval stage of the European fire salamander (Salamandra salamandra) inhabits both lentic and lotic habitats. In the latter, they are constantly exposed to unidirectional water flow, which has been shown to cause downstream drift in a variety of taxa. In this study, a closed artificial creek, which allowed us to keep the water flow constant over time and, at the same time, to simulates with predefined water quantities and durations, was used to examine the individual movement patterns of marked larval fire salamanders exposed to unidirectional flow. Movements were tracked by marking the larvae with VIAlpha tags individually and by using downstream and upstream traps. Most individuals showed stationarity, while downstream drift dominated the overall movement pattern. Upstream movements were rare and occurred only on small distances of about 30 cm; downstream drift distances exceeded 10 m (until next downstream trap). The simulated flood events increased drift rates significantly, even several days after the flood simulation experiments. Drift probability increased with decreasing body size and decreasing nutritional status. Our results support the production hypothesis as an explanation for the movements of European fire salamander larvae within creeks.

Non-random orientation of Pocillopora colonies on forereefs of Moorea, French Polynesia

Morphological variation in scleractinian corals has been variously ascribed to genetic differentiation and phenotypic plasticity, with a likely influence of both factors. Experimental approaches have dominated studies of phenotypic plasticity, for example with asymmetrical colony formation resulting from exposure to experimentally imposed unidirectional water flow. However, it has been difficult to disentangle the effects of competition for space between sessile organisms from the influence of physical forcing on coral morphologies in situ. To this end, we investigated morphological variation of coral colonies of the genus Pocillopora on reefs in Moorea, French Polynesia, where recovery (by 2018) after near complete loss of coral cover on the forereef in 2010 was driven predominantly by recruitment and growth of Pocillopora. We employed a large-area imaging approach at 8 study sites in the forereef of Moorea, constructing digital models of 100 m2 benthic plots to describe the orientation of ~400 individual colonies of Pocillopora. Results demonstrate that Pocillopora colonies on the forereef of Moorea exhibit non-random orientations, with a systematic orientation of the major axis that lies approximately perpendicular to the 20-30 m isobath.

Riverine complexity and life history inform restoration in riparian environments in the southwestern United States

Riparian habitat in the southwestern United States has undergone substantial degradation over the past century, prompting extensive management and restoration of these critical ecosystems. Most restoration efforts, however, do not account for life history traits or riverine complexity that may influence genetic diversity and structure. Here, we use simple sequence repeat markers in four southwestern riparian species (Populus fremontii, Salix gooddingii, S. exigua, and Prosopis glandulosa) that occupy a geographically complex region to address four questions: (1) How is river connectivity related to genetic diversity and structure? (2) How do mating systems and dispersal mechanisms influence gene flow? (3) Is genetic diversity influenced by unidirectional water flow? (4) How do unregulated tributary and regulated river flows affect clonality and associated diversity? Our results identify five findings: (1) Patterns of genetic diversity and structure vary substantially across different species; (2) species with geographic distributions that include a large, perennial river exhibit the least genetic structure; (3) mating system, clonality, and seed dispersal are related to genetic structure; (4) genetic diversity is variable among species and populations, but does not increase or decrease unidirectionally; and (5) clonality and associated diversity does not differ along a regulated river relative to unregulated tributaries. Our multispecies approach to understanding how riverine complexity and life history traits influence genetic diversity and structure could be incorporated into management efforts to more closely match riparian species with their unique environments, thereby facilitating restoration success.

A Step-by-Step Process-Induced Unidirectional Oriented Water Wire in the Nanotube.

The orientation of water molecules is a key requirement for the fast transport of water in nanotubes. It has been accepted that the flip of the water chain follows a concerted mechanism, which has led to the view that bidirectional water flux in nanotubes can be transformed into unidirectional transport when the orientation of water molecules is maintained in long nanotubes under the external field. In this Letter, on the basis of molecular dynamics simulations and first-principles calculations, we confirmed that the flip of the water chain is a step-by-step process, which is different from the perceived concerted mechanism. Further analysis indicated that without an external field, it needed more than 20 water molecules to maintain the unidirectional single-file water flow in a carbon nanotube at a duration time of seconds. Considering that the thickness of the cell membrane (normally 5-10 nm) is larger than the length threshold of the unidirectional water wire, this study suggested that it may not require the external field to maintain the unidirectional flow in the water channel at the macroscopic time scale.

Experimental study on the stable morphology and self-attraction effect of subaqueous barchan dunes

The evolutionary process of isolated dunes under the action of a unidirectional steady water flow is recorded from a bottom-up visual angle by optical synchronization imaging measurements. The morphological characteristics of dunes formed from different initial sand pile configurations are analyzed by an image-processing method. Results show that the trend of reproducing the crescent shape of the dune is shown in all sand piles, which is independent of the initial configuration. The triangular initial sand pile is found to be the first to stabilize to a crescent shape, whereas the square initial sand pile takes the longest time to form a stable crescent shape. This finding is essentially due to the shape effect of the triangle, which effectively reduces the amount of transverse moving sand particles. Based on the aspect ratio of the barchan dune that is stable at approximately 1, we determine that the evolution time required for the final stability of barchan dunes reproduced from different initial sand piles is approximately 200 s within the restriction of the present closed-water-tunnel experimental condition. Moreover, a dimensionless comparison of the profile curves of barchan dunes’ stable morphologies reveals a “streamwise–spanwise” dimension of the dune, which essentially synthesizes characteristic information about windward face and two horns. This “streamwise–spanwise” dimension ultimately presents the self-attraction effect of the crescent shape.

Nutrients, eutrophication and harmful algal blooms along the freshwater to marine continuum

AbstractAgricultural, urban and industrial activities have dramatically increased aquatic nitrogen and phosphorus pollution (eutrophication), threatening water quality and biotic integrity from headwater streams to coastal areas world‐wide. Eutrophication creates multiple problems, including hypoxic “dead zones” that reduce fish and shellfish production; harmful algal blooms that create taste and odor problems and threaten the safety of drinking water and aquatic food supplies; stimulation of greenhouse gas releases; and degradation of cultural and social values of these waters. Conservative estimates of annual costs of eutrophication have indicated $1 billion losses for European coastal waters and $2.4 billion for lakes and streams in the United States. Scientists have debated whether phosphorus, nitrogen, or both need to be reduced to control eutrophication along the freshwater to marine continuum, but many management agencies worldwide are increasingly opting for dual control. The unidirectional flow of water and nutrients through streams, rivers, lakes, estuaries and ultimately coastal oceans adds additional complexity, as each of these ecosystems may be limited by different factors. Consequently, the reduction of just one nutrient upstream to control eutrophication can allow the export of other nutrients downstream where they may stimulate algal production. The technology exists for controlling eutrophication, but many challenges remain for understanding and managing this global environmental problem.This article is categorized under:Science of Water > Water QualityWater and Life > Stresses and Pressures on Ecosystems

Feeding kinematics and morphology of the alligator gar (Atractosteus spatula, Lacépède, 1803).

Living gars are a small clade of seven species that occupy an important position on the actinopterygian phylogenetic tree as members of Holostei, sister-group to teleosts, and exhibit many plesiomorphic traits used to interpret and reconstruct early osteichthyan feeding mechanisms. Previous studies of gar feeding kinematics have focused on the ram-based, lateral-snapping mode of prey capture found in the narrow-snouted Lepisosteus genus, whereas this study focuses on a member of the broad-snouted Atractosteus sister-genus, the alligator gar (Atractosteus spatula, Lacépède, 1803). High-speed videography reveals that the feeding system of alligator gars is capable of rapid expansion from anterior to posterior, timed in a way to generate suction, counteract the effects of a bow-wave during ram-feeding, and direct a unidirectional flow of water through the feeding system. Reconstructed contrast-enhanced μCT-based cranial anatomy and three-dimensional modeling of linkage mechanics show that a lateral-sliding palatoquadrate, flexible intrasuspensorial joint, pivoting interhyal, and retractable pectoral girdle increase the range of motion and expansive capabilities of the alligator gar feeding mechanism. Reconstructions of muscular anatomy, inferences from in vivo kinematics, and in situ manipulations show that input from the hyoid constrictors and hypaxials play an important role in decoupling and modulating the dual roles of the sternohyoideus during feeding: hyoid retraction (jaw opening) and hyoid rotation (pharyngeal expansion). The alligator gar possesses an intricate feeding mechanism, capable of precise control with plesiomorphic muscles that represent one of the many ways the ancestral osteichthyan feeding mechanism has been modified for prey capture.

Effect of Seagrass on Current Speed: Importance of Flexibility vs. Shoot Density

Water flow through seagrass beds transports nutrients, affects sediment stability and chemistry, and imposes hydrodynamic forces on shoots that alter canopy configuration. Past studies done under diverse conditions yielded conflicting results about the effects of shoot density on flow through seagrass bed canopies. We used eelgrass, Zostera marina, to study how the density of flexible shoots affect the hydrodynamics of seagrass beds (canopies) in unidirectional water flow. By exposing randomly-arranged shoots of uniform length to current velocities controlled in a flume, the effects of shoot density and downstream distance (position) could be determined without confounding factors. Comparison of velocity profiles within beds to those upstream of the beds showed that flow was slower in the beds. However, shoot density, position, and current velocity did not affect the percent reduction in flow velocity in a (sea)grass bed. Turbulence enhances mixing of substances carried in the water. Here, turbulence intensity (index of the importance of turbulent velocity fluctuations relative to average current velocity) was lower when ambient flow was faster, but was not affected by shoot density or position, Drag, the hydrodynamic force on a shoot that bends it over in the flow direction, provides another measure of how the canopy affects flow experienced by a shoot. Drag was not affected by current velocity, shoot density, or position in the bed. Gaps between shoots can enhance light and flow penetration into the canopy, but when shoots are bent over by flow, they can cover gaps. Faster ambient currents caused greater gap closure, which at each current speed was greater for high shoot densities. Thus, canopy gap closure did not correlate with percent flow reduction in grass beds or with drag on individual shoots, both of which were independent of shoot density and ambient current velocity. Since changing shoot density does not affect the flow in a grass bed exposed to a given ambient current, our results are inconsistent with the hypothesis that the high shoot densities observed in grass beds in habitats exposed to rapid flow are due to a direct, adaptive response of the grass to the flow environment.

Determinants of parasite distribution in Arctic charr populations: catchment structure versus dispersal potential.

Parasite distribution patterns in lotic catchments are driven by the combined influences of unidirectional water flow and the mobility of the most mobile host. However, the importance of such drivers in catchments dominated by lentic habitats are poorly understood. We examined parasite populations of Arctic charr Salvelinus alpinus from a series of linear-connected lakes in northern Norway to assess the generality of lotic-derived catchment-scale parasite assemblage patterns. Our results demonstrated that the abundance of most parasite taxa increased from the upper to lower catchment. Allogenic taxa (piscivorous birds as final host) were present throughout the entire catchment, whereas their autogenic counterparts (charr as final hosts) demonstrated restricted distributions, thus supporting the theory that the mobility of the most mobile host determines taxa-specific parasite distribution patterns. Overall, catchment-wide parasite abundance and distribution patterns in this lentic-dominated system were in accordance with those reported for lotic systems. Additionally, our study highlighted that upper catchment regions may be inadequate reservoirs to facilitate recolonization of parasite communities in the event of downstream environmental perturbations.

A wave energy system based on converting wave-induced motions into peristaltic flow in a rectangular channel

Energy from the waves at sea is one of the areas that has been an area of interest of the engineering communities worldwide. Recent decades have witnessed the development of various wave energy systems, using various schemes and principles. The main challenge for most systems in efficient energy converting is posed by converting energy into a usable form from the reciprocating wave induced motions due to the harmonic motion of water particles.The authors have conceived a scheme to convert the harmonic motions of water particles which manifest themselves as the near-sinusoidal motion of the free water surface into a unidirectional water flow that can be exploited for harvesting energy: An array of buoys that are arranged in a line perpendicular to the wave direction, that are allowed to oscillate in heaving motion. The heaving motion enforces a series of actuators to induce a sinusoidal motion to a diaphragm sheet placed inside a rectangular channel, which is placed beneath the free surface at a sufficient depth. The motion of the diaphragm sheet shall result in the peristaltic motion of the otherwise stagnant water. The mass of flowing water peristaltic-pumped then can be channelled to a turbine from which energy can be obtained.

Incipient Motion of Shells and Shell Gravel

AbstractIncipient motion of seashells under a unidirectional flow of water in a horizontal open channel over surfaces with differing roughnesses and shell placements is investigated experimentally....

Unidirectional Transport of Water through an Asymmetrically Charged Rotating Carbon Nanotube

Achieving a high speed, unidirectional water flow through carbon nanotubes (CNTs) is a key factor in designing novel nanofluidic devices. In this study, utilizing molecular dynamics (MD) simulations, we propose a novel nanoscale water pump for directed water transportation using charged rotating CNTs. Two basic conditions for stable water flow, including thermodynamic nonequilibrium and spatial asymmetry, are provided by introducing partial charges on carbon atoms of the channel with asymmetric patterns and its rotation, respectively. We demonstrate that the performance of the water pump is proportional to the gradient of a linear charge distribution and angular velocity of the rotation. Our results indicate that, in a constant total charge, there is a linear relationship between water flux and charge difference of the nanotube ends. In addition there is a logarithmic relationship between the water flux and the nanotube angular velocity. In fact, there is no considerable flux when the nanotube is rotating...

Design of Nano Screw Pump for Water Transport and its Mechanisms

Nanopumps conducting fluids through nanochannels have attracted considerable interest for their potential applications in nanofiltration, water desalination and drug delivery. Here, we demonstrate by molecular dynamics (MD) simulations that a nano screw pump is designed with helical nanowires embedded in a nanochannel, which can be used to drive unidirectional water flow. Such helical nanowires have been successfully synthesized in many experiments. By investigating the water transport mechanism through nano screw pumps with different configuration parameters, three transport modes were observed: cluster-by-cluster, pseudo-continuous, and linear-continuous, in which the water flux increases linearly with the rotating speed. The influences of the nanowires’ surface energy and the screw’s diameter on water transport were also investigated. Results showed that the water flux rate increases as the decreasing wettability of helical nanowires. The deviation in water flux in screw pumps with smaller radius is attributed to the weak hydrogen bonding due to space confinement and the hydrophobic blade. Moreover, we also proposed that such screw pumps with appropriate diameter and screw pitch can be used for water desalination. The study provides an insight into the design of multifunctional nanodevices for not only water transport but water desalination in practical applications.

A Hybrid Continuous/Discrete-Time Model for Invasion Dynamics of Zebra Mussels in Rivers

While some species spread upstream in river environments, not all invasive species are successful in spreading upriver. Here the dynamics of unidirectional water flow found in rivers can play a role in determining invasion success. We develop a continuous-discrete hybrid benthic-drift population model to describe the dynamics of invasive freshwater mussels in rivers. In the model, a reaction-advection-diffusion equation coupled to an ordinary differential equation describes the larval dispersal in the drift until settling to the benthos, while two difference equations describe the population growth on the benthos. We study the population persistence criteria based on three related measures: fundamental niche, source-sink distribution, and net reproductive rate. We calculate the critical domain size in a bounded domain by analyzing a next generation operator. We analyze the upstream and downstream spreading speeds in an unbounded domain. The model is parameterized by available data in the literature. Combi...