Influence Of Hydrodynamics Research Articles

Morphological Characteristics and Hydrological Connectivity Evaluation of Tidal Creeks in Coastal Wetlands

Tidal creeks play a critical role in delivering water, suspended sediments, and nutrients to coastal wetlands, so it is important to understand the characteristics of the tidal creek system to guide the development and sustainable utilization of coastal wetlands. Using the coastal wetlands of the Liao River Estuary (LRE) as a study area, this study accurately divided the tidal flat based on the principle of tidal correction, extracted the linear features of tidal creeks using high-resolution remote sensing (RS) data, and then classified the tidal creeks on a tidal flat using the tidal creek ordering algorithm. Our study aimed to quantify the morphological characteristics of tidal creeks and qualitatively evaluate the parameters of the tidal creek network in the study area. The study results show obvious spatial heterogeneity in the order and the average length of tidal creeks in the coastal wetlands of the LRE. With the increase in the order of tidal creeks, the average length of tidal creeks increased exponentially and the number of tidal creeks decreased exponentially in the study area. The total density of tidal creeks was related to the beach surface elevation gradient, and the density and frequency of tidal creeks reduced substantially with an increase in the order of tidal creeks. The sinuosity ratio of tidal creeks declined sharply with a fall in the beach surface elevation gradient. The average bifurcation ratio of tidal creeks in the upper intertidal zone was higher than that in other zones, indicating that the tidal creeks in the upper intertidal zone were erratic. In addition, the hydrological connectivity of the tidal creek network in the upper intertidal zone and the development of the tidal creek system in the supratidal zone were the highest in the LRE. The study results help understand the spatial variations in tidal creek morphology under the influence of tidal hydrodynamics.

The isotopic composition of organic carbon, nitrogen and provenance of organic matter in surface sediment from the Jiangsu tidal flat, southwestern Yellow Sea

The Jiangsu tidal flat is a significant organic matter reservoir, but quantitative studies of organic matter sources are scarce. In this study, total organic carbon (TOC) and total nitrogen (TN) concentrations and δ13Corg and δ15Ntotal values of surface sediment from Jiangsu tidal flat were investigated for their distributions, influencing factors, and sources of organic matter. TOC and TN were high in the center of study area and correlated well with grain size, indicating hydrodynamic influence on organic matter. High TOC/TN and low δ13Corg and δ15Ntotal in estuaries were characteristic of C3 plants, soil, and fertilizer sources, suggesting source effect on the distribution of organic matter. The MixSIAR model revealed that marine sources were dominant with a contribution reaching 56.9 %, followed by uniform of C3 plants, soil and fertilizer, while domestic sewage was least prominent. This study enriched theories of the biogeochemical cycle and ecological protection in the southwestern Yellow Sea.

Source Apportionment, Hydrodynamic Influence, and Environmental Stress of Pharmaceuticals in a Microtidal Estuary with Multiple Outlets in South China.

Pharmaceutical residues in the environment are of great concern as ubiquitous emerging contaminants. This study investigated the presence of 40 pharmaceuticals in water and sediment of the Pearl River Estuary (PRE) in the wet season of 2020. Among psychiatric drugs, only diazepam was found in water samples while six of them were detected in the sediment. The Σantibiotics levels ranged from 6.18 to 35.9 ng/L and 2.63 to 140 ng/g dry weight in water and sediment samples, respectively. Fluoroquinolones and tetracyclines were found well settling in the outlet sediment, while sulfonamides could be released from disturbed sediment under stronger tidal wash-out conditions. After entering the marine waters, pharmaceuticals tended to deposit at the PRE mouth by the influence of the plume bulge and onshore invasion of deep shelf waters. Low ecological risks to the aquatic organisms and of causing antimicrobial resistance were identified. Likewise, hydrological modeling results revealed insignificant risks: erythromycin-H2O and sulfamethoxazole discharged through the outlets constituted 30.8% and 6.74% of their environmental capacity, respectively. Source apportionment revealed that pharmaceutical discharges through the Humen and Yamen outlets were predominantly of animal origin. Overall, our findings provide strategic insights on environmental regulations to further minimize the environmental stress of pharmaceuticals in the PRE.

Distribution, Sources, and Dynamics of Particulate Matter Along Trans‐Arctic Sections

AbstractIn order to better understand the sources, sinks, and hydrodynamic influences on particulate matter distribution and variability in Arctic basins, we combined transmissometer data from two 2015 fall expeditions: one from Bering Strait (USCGC Healy) and the other from Barents Sea (R/V Polarstern) meeting at the North Pole. These first trans‐Arctic sections of beam attenuation were overlain by salinity, temperature, and chlorophyll‐a fluorescence (Chl‐a) contours. Chl‐a sections were overlain by nitrate contours. Particle composition analyzed from filtered samples throughout the full water column aided significantly in discerning sources, distribution, and dynamics of particles. Dense Pacific water moving swiftly through Bering Strait erodes and carries sediment‐laden waters onto the Chukchi Shelf and into the Canada Basin. This nutrient‐rich Pacific water sinks below a low‐salinity, nutrient‐poor polar mixed layer, forming a thick lens of high salinity water known as Pacific halocline water (salinity 31–33). Ice and the nutrient‐poor mixed layer inhibit photosynthesis in surface waters of Canada and Makarov Basins, but subsurface chlorophyll‐a maxima are observed if nutrients and light are available. Surface‐water biomass is greater in the Barents Sea than in the Beaufort Gyre because nutrient‐rich Atlantic water entering Barents Sea is not isolated from surface waters by ice or strong stratification. Surface water cools, creating high‐density water that cascades into ∼400 m basins in Barents Sea and into deep Nansen Basin, eroding sediment that creates patches of nepheloid layers in the shallow basins. Intense nepheloid layers in the deep basins are rare, suggesting weak bottom currents.

Oil biodegradation in permeable marine sediments: Effects of benthic pore-water advection and solute exchange

Oil spills have been recognized as among the worst kinds of environmental disasters, causing severe coastal ecological and economic damages. Although benthic flow and solute fluxes are known to have strong impacts on fate and transport of oil deposited within marine sediments, their endogenous mechanisms still remain to be uncovered. In this paper, simulations of flow and solute transport processes along with hydrocarbon biodegradation were conducted in a cylindrical benthic chamber system to investigate influences of benthic hydrodynamics on oil biodegradation in permeable marine sediments. Results show that ripple-flow interactions create subsurface recirculation cells whereby seawater infiltrates into the benthic sediments at ripple troughs while groundwater discharges near the crests. It results in a spatially varied oil biodegradation rate in marine sediments. Significant oil biodegradation occurs near sediment ripple troughs due to direct oxygen recharge, while biodegradation of oil deposited uphill becomes slow due to limited oxygen replenishment. Oil biodegradation decreases subsurface oxygen content, and consequently impedes discharge of oxygen from benthic sediments. Our results reveal a dynamic interaction between oil biodegradation and benthic flow and solute transport processes, which has strong implications for predicting oil persistence and biodegradation within marine sediments and its associated impacts on benthic biogeochemical processes.

Sedimentary geochemistry of Late Cretaceous-Paleocene deposits at the southwestern margin of the Anambra Basin (Nigeria): Implications for paleoenvironmental reconstructions

The Campano-Maastrichtian deposits of the Nkporo and Mamu formations of the Anambra Basin represent prospective hydrocarbon resources in southern Nigeria. In order to reveal the paleoclimate, sediment recycling and paleoenvironment during the deposition of these formations in the southwestern portion of the Anambra Basin, a detailed geochemical analysis was performed using major elements, trace elements and rare earth element data, as well as the mineralogical characterization of 20 samples from two wells. The combination of geochemical ratios (Rb/Sr, Th/U, and C-value) and weathering indices (CIA, CIW, and PIA) demonstrates that the region experienced a warm, humid tropical paleoclimate throughout the Late Cretaceous. Furthermore, West Africa experienced strong precipitation during the Cretaceous, leading to intense chemical weathering in the region, as documented by the geochemically matured sediments.The paleosalinity (Sr/Ba) and paleoproductivity (Ba/Al and P/Ti) proxies show that the studied mudrocks were deposited primarily in brackish to shallow-marine settings, with poor primary productivity due to terrestrial clastic influx and hydrodynamic influence. Using multiple paleoredox indicators, deposition under oxic conditions is detected. The low authigenic U enrichment and depleted V and Cr values normalized to UCC standards further support oxic bottom water conditions. Wavy laminations observed in the mudrocks indicate retreating seawater and high hydrodynamic conditions. Ultimately, the southwestern Anambra Basin reveals Late Cretaceous-Paleocene deposits of a shallow sea controlled by a strong hydrodynamic regime.

Experimental and numerical studies of separation intensification in segmented flow microreactors

Process intensification studies have already been well-established in continuous operations, particularly achieved by using microreactors. Separation intensification benefits from the application of process intensification and shows great potential, yet it is still not sufficiently studied. In this work, liquid-liquid two-phase segmented flow capillary microreactors and simulation models based on finite element method were used to perform experimental and numerical studies on the extractive separation intensification of the Zn-Cd-Mn system, respectively. The influence of hydrodynamics including metal ion concentration, plug velocity, and initial pH of the aqueous phase on the separation factor was explored. By regulating the hydrodynamic conditions, higher separation factors are obtained in shorter times to achieve separation intensification. The Damkhler number (Da) was introduced to clarify the rate-determining step and elaborate the separation mechanism. During the simulations, the results obtained from the model based on the finite element method agree well with the experimental ones. Taking advantage of the strong complementarity between numerical and experimental studies, separation intensification can be more deeply understood.

Zoning Study on Influence Intensity of Cao’e River Sluice on River Network Drainage Based on 2D Numerical Model

Shaoxing City is located in the central and northern part of Zhejiang Province, generally showing the topographic trend of high in the South and high in the North. The South is mountainous and the North is plain. There are many rivers in the river network, which are staggered and complex. A two-dimensional mathematical model for flood control and drainage of river network in Shaoxing plain is established, the hydrodynamic influence of Cao’e River gate on river network in different regions is studied, and the characteristics of each region are analyzed. According to the zoning of the impact intensity of Cao’e River sluice on river network hydrodynamic force, six obvious zoning from strong to weak are obtained, and the characteristics of each region are analyzed. It has reference value for comprehensively formulating sluice dispatching operation procedures, changing river network hydrodynamic force distribution and other non-engineering countermeasures, and provides decision-making basis for river network comprehensive management and hydrodynamic force utilization.

Role of hydrodynamics in shaping chemical habitats and modulating the responses of coastal benthic systems to ocean global change.

Marine coastal zones are highly productive, and dominated by engineer species (e.g. macrophytes, molluscs, corals) that modify the chemistry of their surrounding seawater via their metabolism, causing substantial fluctuations in oxygen, dissolved inorganic carbon, pH, and nutrients. The magnitude of these biologically driven chemical fluctuations is regulated by hydrodynamics, can exceed values predicted for the future open ocean, and creates chemical patchiness in subtidal areas at various spatial (µm to meters) and temporal (minutes to months) scales. Although the role of hydrodynamics is well explored for planktonic communities, its influence as a crucial driver of benthic organism and community functioning is poorly addressed, particularly in the context of ocean global change. Hydrodynamics can directly modulate organismal physiological activity or indirectly influence an organism's performance by modifying its habitat. This review addresses recent developments in (i) the influence of hydrodynamics on the biological activity of engineer species, (ii) the description of chemical habitats resulting from the interaction between hydrodynamics and biological activity, (iii) the role of these chemical habitat as refugia against ocean acidification and deoxygenation, and (iv) how species living in such chemical habitats may respond to ocean global change. Recommendations are provided to integrate the effect of hydrodynamics and environmental fluctuations in future research, to better predict the responses of coastal benthic ecosystems to ongoing ocean global change.

Towards realistic power performance and techno-economic performance of wave power farms: The impact of control strategies and wave climates

This paper performs an investigation of power performance and techno-economic performance of wave power farms in realistic wave climates, where hydrodynamic interaction and influence of control strategies employed by power take-off systems are fully considered in mathematical modeling and numerical analysis. This is of great significance for a commercial wave power farm operated in a specific sea site over a long time of years, as wave energy converters will encounter a wide range of sea states, which requires that associated power take-off systems of individual units must be controlled accordingly to maximize the converted energy and to reduce the levelized cost of energy (LCOE). To that end, a fully-coupled numerical model, where the power take-off systems of wave energy converters are coordinately controlled/tuned for each sea state by employing an optimal linear passive control strategy and an optimal active control strategy, respectively. Numerical results show that power performance and LCOE of wave power farms vary over wave climates, and machinery constraints of power take-off force must be considered. Globally coordinated control of wave power farms by employing a constrained optimal linear active control strategy yields a LCOE of 0.17−0.54 $/kWh and increases the annual energy generation at least three times in specific wave climates of China, United States, Australia and Ireland.

Backward Location and Travel Time Probabilities for Pollutants Moving in Three-Dimensional Aquifers: Governing Equations and Scale Effect

Backward probabilities have been used for decades to track hydrologic targets such as pollutants in water, but the convenient deviation and scale effect of backward probabilities remain unknown. This study derived backward probabilities for groundwater pollutants and evaluated their scale effect in heterogeneous aquifers. Three particle-moving methods, including the backward-in-time discrete random-walk (DRW), the backward-in-time continuous time random-walk (CTRW), and the particle mass balance, were proposed to derive the governing equation of backward location and travel time probabilities of contaminants. The resultant governing equations verified Kolmogorov’s backward equation and extended it to transient flow fields and aquifers with spatially varying porosity values. An improved backward-in-time random walk particle tracking technique was then applied to approximate the backward probabilities. Next, the scale effect of backward probabilities of contamination was analyzed quantitatively. Numerical results showed that the backward probabilities were sensitive to the vertical location and length of screened intervals in a three-dimensional heterogeneous alluvial aquifer, whereas the variation in borehole diameters did not influence the backward probabilities. The scale effect of backward probabilities was due to different flow paths reaching individual intervals under strong influences of subsurface hydrodynamics and heterogeneity distributions, even when the well screen was as short as ~2 m and surrounded by highly permeable sediments. Further analysis indicated that if the scale effect was ignored, significant errors may appear in applications of backward probabilities of groundwater contamination. This study, therefore, provides convenient methods to build backward probability models and sheds light on applications relying on backward probabilities with a scale effect.

Geometric and hydrodynamic influences on the droplet breakup dynamics in a branched microdevice

Droplet breakup phenomenon in a microchannel is a well-known potential approach for process intensification. Here we investigate a branched microdevice to explore the influence of Capillary number (Ca) and the ratio of branching arm width to the main channel (β) on droplet breakup dynamics by developing a 3-D computational model, which was firstly validated with the in-house as well as independent experimental results. A homogeneous pressure field inside a droplet is found to be the principal reason in droplet non-breakup for widely asymmetric configuration (i.e., β = 0.4 and 1.2). For other branching configurations (β = 0.6, 0.8 and 1.0), droplet breakup in three different regimes is identified, and a regime map is formulated as a function of Ca vs. β. It is observed that apart from Ca, a critical β also exists for the transition between breakup and non-breakup regimes, and the configuration with β = 0.8 is more susceptible for droplet breakup owing to the force balance in both arms with respect to confinement and flow direction. Additionally, the smaller critical Ca for β = 1.0 than for β = 0.6 indicates the significance of upstream flow distribution.

Hydrodynamic and Morphodynamic Influences from Ocean Current Energy Conversion Sites in the South–Southeastern Brazilian Inner Shelf

As marine renewable resources begin to become a feasible energy source, it becomes crucial to investigate the nearshore impact of hydrodynamic and morphodynamic processes. As part of the implementation of turbines in the numerical modeling environment of Telemac-3D and Sisyphe modules, we conducted a 10-year run to evaluate nearshore impacts of turbines in the flow. We used five criteria to define viable locations. Turbines sites were added to a conversion energy model coupled into the hydrodynamic model in order to develop properly the flow changes towards the energy conversion process. The results revealed that in the three chosen spots, turbines were not converting equally the current energy within the site. In fact, the turbines located on the outer side of the farm developed greater conversion rates. This impacted the nearshore in the following ways: (1) the decrease in the currents intensity that generates strong adjustments in the water column, breaking the natural pattern of vertical circulation; (2) development of lateral flows that in time affects the bottom dynamics and results in changes in sediment deposition; and (3) increase in bedload transport rates around the turbine’s field due to divergence in the flow. The idealized turbines sites produced 1,775 GWh in 10 years, which could provide electricity to 54,181 residences during this period.

A numerical study of hydrodynamic influence on collision of brash ice with a structural plate

A numerical study of hydrodynamic influence on collision of brash ice with a structural plate

Estimation of surface wave induced fluid mud thickness on the seafloor

Mud-induced dissipation of surface wave energy is a key mechanism that affects wave propagation in muddy environments. The properties of fluid mud on seafloors required to simulate wave dissipation over shallow waters are often unknown in investigations where wave energy reduction over onshore fetch is a key factor in design of coastal infrastructure. Direct observation and estimation of the thickness of fluid mud on seafloors are complicated; this brings a major complication against accurate prediction of waves in muddy environments. As a step towards filling this gap, this study presents for the first time the estimation of the thickness of fluid mud layers surface waves generate over muddy shelves, using three methods : (1) a method based on vertical structure of acoustic backscatter that requires less assumptions, (2) a mass balance based on vertical structure of sediment concentration, and (3) an empirical approach. Comprehensive field observations of wave–mud interaction were collected for two months at 4 m water depth and analyzed here. The results, assumptions, and approaches of these three methods are evaluated. The analysis of the field observations and the estimates show that fluid mud layers formed in the wake of four significant frontal storms with relatively strong low-frequency swell energy (wave periods ≥ 7 s) during which the wave-induced orbital velocity at the bed exceeded the same threshold of ub∼ 0.5 m/s. The thickness of fluid mud layers varied between 4 cm and 15 cm among the four events. Using an onset density of fluid mud based on laboratory experiments, the mass balance method gives fluid mud thicknesses that agree with, but underestimating, the results of the acoustic backscatter method. The empirical approach agrees best with the acoustic backscatter method, when a settling velocity of 3.5 mm/s and a hydraulic roughness of 0.001 m are used, in agreement with the previous sediment and hydrodynamic data collected at the study site. Applicability of these methods to determine fluid mud thickness at other locations requires accurate description of sediment conditions near the seafloor under the influence of surface waves and hydrodynamics.

Flow boiling of carbon dioxide with a micro impinging jet

Flow boiling of carbon dioxide with a micro impinging jet was experimentally studied. The flow was issued from a 206 µm diameter nozzle onto a fused silica substrate that held a serpentine heater and three concentrically distributed resistance temperature detectors (RTDs). The effects of heat flux, radial position, mass flux, and pressure were experimentally studied. Heat fluxes up to 140 W/cm2, mass fluxes from 0.7 to 2.4 kg/cm2s, and saturation temperatures from 16.5 to 26.7 °C, corresponding to pressures of ∼ 5.3 to 6.7 MPa, respectively, were studied. To reveal the heat flux, radial position, and mass flux effects, the fluid entered at a temperature of 21.2 °C and a pressure of 5.9 MPa, which was around the saturation conditions of CO2, resulting in a rapid onset of nucleate boiling in most of the experiments. Results showed an increase in the heat transfer coefficient with heat flux, mass flux, and pressure up until the critical heat flux condition. In contrast, the heat transfer coefficient declined with radial position characterized by a pronounced influence of the jet hydrodynamics. Finally, comparisons with available correlations showed discrepancies, resulting in the proposal of a new correlation.

Spatial self-organization of marine agglutinated microbial carbonate build-ups: Insights from stratigraphic forward modelling using Stromatobyte3D

Microbialites span a substantial fraction of Earth history, and have important meanings for understanding long-term history of life and environment. Key controls on microbialite morphology and distribution include substrate topography, hydrodynamic conditions, water depth, salinity, light intensity, and sedimentation rates. This leads to potentially complex combinations of control by internal spatial feedbacks and also external factors. This complexity is explored here using Stromatobyte3D, a new numerical stratigraphic forward model that calculates microbialite accumulation due to in-situ precipitation, sediment trapping and binding, and sedimentation from suspension, controlled by evolving topography and water flow due to waves, tides or other currents. Results show that with increasingly strong spatial interactions of microbialite growth with water and suspended sediment, particularly the influence of hydrodynamics on in-situ microbialite growth and suspended sediment deposition patterns, three distinct microbialite morphologies are produced, from isolated columns, through elongated mounds, to ridges elongated in the dominant flow direction. Quantitative analysis demonstrates a dominant antecedent substrate topographic control on microbialite nucleation and growth in the absence of water flow, declining as hydrodynamic processes and strong spatial interactions are introduced causing mounds to accrete and coalesce laterally in the flow direction. Formation of coherent morphological patterns, produced by spatial interactions between topography, hydrodynamics, microbialite growth, and sedimentation from suspension, and independent of initial condition, is evidence of spatial self-organization. Modelled morphologies are strikingly similar to observations from modern marine agglutinated microbialite strata, suggesting modelled processes and their behaviours are realistic, and can therefore be useful to assist field interpretations of observed microbialite morphologies where similar processes were operating together.

Active Nematodynamics on Curved Surfaces – The Influence of Geometric Forces on Motion Patterns of Topological Defects

We derive and numerically solve a surface active nematodynamics model. We validate the numerical approach on a sphere and analyse the influence of hydrodynamics on the oscillatory motion of topological defects. For ellipsoidal surfaces the influence of geometric forces on these motion patterns is addressed by taking into account the effects of intrinsic as well as extrinsic curvature contributions. The numerical experiments demonstrate the stronger coupling with geometric properties if extrinsic curvature contributions are present and provide a possibility to tune flow and defect motion by surface properties.

The Influence of Electrolyte Flow Hydrodynamics on the Performance of a Microfluidic Dye-Sensitized Solar Cell

The dye-sensitized solar cells microfluidically integrated with a redox flow battery (µDSSC-RFB) belong to a new emerging class of green energy sources with an inherent opportunity for energy storage. The successful engineering of microfluidically linked systems is, however, a challenging subject, as the hydrodynamics of electrolyte flow influences the electron and species transport in the system in several ways. In the article, we have analyzed the microflows hydrodynamics by means of the lattice-Boltzmann method, using the algebraic solution of the Navier-Stokes equation for a duct flow and experimentally by the micro particle image velocimetry method. Several prototypes of µDSSC were prepared and tested under different flow conditions. The efficiency of serpentine µDSSC raised from 2.8% for stationary conditions to 3.1% for electrolyte flow above 20 mL/h, while the fill factor increased about 13% and open-circuit voltage from an initial 0.715 V to 0.745 V. Although the hexagonal or circular configurations are the straightforward extensions of standard photo chambers of solar cells, those configurations are hydrodynamically less predictable and unfavorable due to large velocity gradients. The serpentine channel configuration with silver fingers would allow for the scaling of the µDSSC-RFB systems to the industrial scale without loss of performance. Furthermore, the deterioration of cell performance over time can be inhibited by the periodic sensitizer regeneration, which is the inherent advantage of µDSSC.

Rheology-modulated alterations in electro-magneto-hydrodynamic flows in a narrow cylindrical capillary: Contrasting trends in high and low surface charge limits.

We investigate electrokinetic transport of power-law fluids in a narrow cylindrical capillary in the presence of a transverse magnetic field. The governing equations including the full Poisson-Boltzmann equation and the Cauchy momentum equation with power-law constitutive behavior are solved numerically, without being restrictive to low surface potential limits. The influence of the power-law index, wall zeta potential, relative strength of electromagnetic force over viscous force (as represented by the Hartmann number), and the lateral electric field strength on the variation of the volumetric flow rate is analyzed. Our results reveal a significant augmentation in the net-throughput beyond the traditionally explored low surface-charge limits, especially for shear-thinning fluids, defying the established notions. These fundamental theoretical premises may act as essential precursors towards developing deeper insights on fluidic transport bio-nanopores under electro-magneto- hydrodynamic influences.