Hydrodynamic Processes Research Articles

Unforeseen nitrate accumulation under nutrient mitigation measures in the east Pearl River Estuary: Phenomenon, drivers and implications

Study regionShenzhen Bay (SZB) in the east Pearl River Estuary, China Study focusEither NO3− or NH4+ is the dominant component of dissolved inorganic nitrogen (DIN) in most estuarine waters, but few studies focused on the mechanisms of ongoing DIN transformations under various hydrologic regimes. This analysis spans 31 years of DIN component changes and involves numerical simulations to identify the roles of various driving factors including runoff and biogeochemical actions. These new insights into DIN change mechanisms from the coupling biogeochemical and hydrodynamic processes would help to boost effective mitigation measures to deal with nitrate accumulation in estuarine waters, thereby supporting integrated land-ocean nutrient management. New hydrological insights for the regionThe dominant DIN component in the SZB was found to transition from NH4+ to NO3− between 1990 and 2020. Particularly in the -upper bay, there was an unexpected increase in the mean concentration fraction of NO3− in DIN, rising from 19.5% (1990‐2017) to 65.5% (2018‐2020). This change can be partially attributed to reduced runoff NH4+ inputs. Both runoff and tidal current can transport NH4+ and NO3−downstream, but the high background levels of NO3− in the lower bay contributed to sustaining NO3− in the upper bay through ebb and flow. Biogeochemical actions further strengthened the decline of NH4+ and the rise of NO3−. Even in scenarios without terrestrial source inputs, the simulated biogeochemical processes continued to help reduce NH4+ levels throughout the bay while increasing NO3− concentrations in the middle and lower bay.

Numerical Study of the Flow and Blockage Ratio of Cylindrical Pier Local Scour

A three-dimensional large eddy simulation model is used to simulate the turbulent flow dynamics around a circular pier in live-bed and clear-water scour conditions. The Navier–Stokes equations are transformed into a σ-coordinate system and solved using a second-order unstructured triangular finite-volume method. We simulate the bed evolution by solving the Exner-Polya equation assisted by a sand-slide model as a correction method. The bedload transport rate is based on the model of Engelund and Fredsœ. The model was validated for live-bed conditions in a wide channel and clear-water conditions in a narrow channel against the experimental data found in the literature. The in-house model NSMP3D can successfully produce both the live-bed and clear-water scouring throughout a stable long-term simulation. The flow model was used to study the effects of the blockage ratio in the flow near the pier in clear-water conditions, particularly the contraction effect at the zone where the scour hole starts to form. The scour depth in the clear water simulations is generally deeper than the live-bed simulations. In clear-water, the results show that the present model is able to qualitatively and quantitatively capture the hydrodynamic and morphodynamic processes near the bed. In comparison to the wide channel situation, the simulations indicate that the scour rate is faster in the narrow channel case.

Optimization of hydrodynamic degumming of flax fiber for improved biochemical profile

Flax fibers have bioactive properties due to their biochemical composition. The quality of the fibers is the main parameter that determines the application, and the process of obtaining fibers has a crucial impact on the composition and properties of fibers. Therefore, this study aimed to enhance the quality of flax fibers by optimizing the hydrodynamic degumming process of decorticated flax fibers. Flax fibers, both non-transgenic (Nike) and transgenic (B14) fibers with overexpression of the β-1,3-glucanase gene from potato, were obtained through nine processes that varied in the degumming temperature, degumming time, and rinsing temperature. The content of phenolic, terpene and polyamine compounds as well as antioxidant activity was determined in the fibers. Two processes, due to having the highest content of bioactive compounds, were selected for further analyses: determination of the chemical composition and structure of plant cell walls, and in vitro tests on the culture of the V79 hamster lung fibroblast cell line. Both processes led to an increase in the content of cellulose and hemicellulose, along with a decrease in the amount of pectin in B14 fibers, indicating changes in the structure of the cell wall. Water extract containing phenolic compounds obtained from flax fiber resulted in increased viability of the V79 fibroblasts and did not show changes in the level of transcripts of inflammatory genes. Based on the obtained results, process VI was identified as the most effective for obtaining flax fibers of the best quality. Additionally, the study confirmed that transgenic B14 fibers exhibited better quality than non-transgenic fibers. The findings highlight the potential of the methods used to obtain flax fibers, which may significantly impact their properties.

A measurement-to-modelling approach to understand catchment-to-reef processes: sediment transport in a highly turbid estuary

As sediments carried by rivers enter coastal waters, fine particles can reduce the amount of light that reaches the reef through light attenuation. The Fitzroy Estuary - Keppel Bay (FE-KB), being the second-largest source of sediments to the Great Barrier Reef (GBR) poses a significant threat to the GBR ecosystem such as coral reefs and seagrass meadows, and biogeochemical cycles that influence water clarity. While monitoring and modelling capabilities for catchment and marine settings are now well-developed and operational, a remaining key gap is to better understand and model the transport, dynamics and fate of catchment derived material through tidally influenced sections of rivers that discharge into the GBR. This study aims to reveal sediment transport in the FE-KB estuary by continuously monitoring the seasonal variability over a year-long period and build a high-resolution model to predict sediment budgets under different scenarios of physical forcing and river conditions. Multiple data sources, including field surveys, historical data, and numerical modelling were used to obtain a detailed understanding of the sediment transport processes during wet (high river flow) and dry (low-to-no river flow) seasons. The use of high-resolution bathymetry and survey data for sediment model parameterization allowed for accurate mapping of the morphological changes, while numerical modeling provided insights into the hydrodynamic and sediment transport processes in the estuary. Observation and model data confirm the existence of a Turbidity Maximum Zone (TMZ) in the FE-KB (approximately 35 – 40 km from estuary head), where the topography plays a critical role in trapping sediments. By utilizing the model, a closed sediment budget was calculated under varying flow conditions and the results were used to determine the estuarine trapping coefficient that ranges from 28% (during extreme wet condition) to 100% (during dry condition) of the total catchment loads. Morphodynamic modelling demonstrated a persistent erosion pattern in the upper reach of the FE. The lower FE and southern tidal creeks serve as a large sediment storage basin during both wet and dry seasons, and sediment is exported and deposited offshore during high river flow conditions.

Characterization of salt wedge intrusion process in a geographically complex microtidal deltaic estuarine system

Deltas are strategic systems of high ecological and economic importance since they provide various environmental resources and fertile alluvial soils. Different types of hydrodynamic processes occur in deltas, including saline intrusion. We implemented a three-dimensional numerical modeling system using the EFDC + Explorer Modeling System to analyze the characteristics of saline intrusion in the Sinú River delta, Colombia. We configured the model with field data from two measurement campaigns in February and November 2021, dry and wet seasons, respectively, and with secondary information. Several climatic conditions to cover a wide range of variability in the main forcing factors were simulated, specifically river discharge and tides: (1) without the influence of the El Niño Southern Oscillation (ENSO) climatic phenomena; (2) under critically low conditions of flow discharge; and (3) with sea level rise forecasts. The model was calibrated using in-situ water velocity data and salinity profiles. We obtained Index of Agreement (d) values between 0.67 and 0.99 for salinity and higher than 0.9 for water velocity. The numerical simulation provides valuable information about this stratified salt wedge system's dynamic nature, mainly due to changes in river discharge. The simulation demonstrated that river discharges above 319 m3/s were sufficient to prevent salt wedge intrusion, which are typical values registered annually between May and November. The scenarios under critical low discharge conditions and sea level rise projections showed a maximum reach of the salt wedge intrusion of 7.40 km. The model proved efficient in evaluating the saline intrusion process in the Sinú River delta, obtaining practical results that describe the dynamics of this process. It was shown that by simulating physical processes, such as salinity stratification, numerical models provide useful information on how these estuarine systems respond to different environmental stress factors associated with current climate variability, such as long drought periods or El Niño South Oscilation (ENSO), since salinity gradients play an important role in deltas' aquatic life, since they influence the distribution of phytoplankton, which is a key player for primary productivity.

Дворівневий метод моделювання руху рідини за допомогою решітчастої моделі Больцмана та згорткової нейронної мережі

A new two-level method for modeling fluid movement in closed surfaces is proposed. The metod simulates an unsteady hydrodynamic process and includes two levels of description of the modeling process. The first level supports the development of the process over time and is implemented based on the Boltzmann lattice model. At the second level, for each time layer, based on the obtained velocity field, the pressure distribution is refined by modeling the solution of the Poisson equation in the working area using a convolutional neural network, which is pre-trained on a training data set formed for a given set of typical problems. A method combi¬ning both technologies is proposed, taking into account the compensation of the compressibi¬lity characteristic. The structure and features of neural network training are described. Experiments were conducted on models simulating the human digestive tract in various states. The performance of the developed method is compared with the numerical way of solving the Poisson equation.

Comparison of Hydrodynamic Processes Modelling Results in Shallow Water Bodies Based on 3D Model and 2D Model Averaged by Depth

Introduction. Two-dimensional hydrodynamic models have proven their ability to adequately describe the processes of runoff and transportation in rivers, lakes, estuaries, deltas and seas. Practice shows that even where significant three-dimensional effects are expected, for example, with wind flows, a two-dimensional approach can work effectively. However, in some cases, the two-dimensional model does not accurately reflect the actual flow structures. For example, in shallow waters with complex bathymetry, heterogeneous terrain and dynamics can lead to a non-uniform velocity profile. The aim of the study is to develop a basis for determining in which cases a two-dimensional model averaged in depth is sufficient for modelling hydrodynamic processes in shallow waters like the Azov Sea, and in which cases it is advisable to use a three-dimensional model to obtain accurate results.Materials and Methods. Local analytical solutions have been obtained for the propagation of the predominant singular progressive wave in a shallow, well-mixed reservoir. Advective terms and Coriolis terms are neglected, the vortex viscosity is assumed to be constant, and the lower friction term is linearized. Special attention is paid to the latter, since the characteristics of the models significantly depend on the method of determining the coefficients of lower friction. The analytical method developed in the study shows that certain combinations of higher flow velocities (u ≈˃ 1 m/s) and water depths (d ˃ 50 m) can cause significant differences between the results of the depth-averaged model and the model containing vertical information.Results. The results obtained are verified by numerical simulation of stationary and non-stationary periodic flows in a schematized rectangular basin. The results obtained as a result of three-dimensional modelling are compared with the results of two-dimensional modelling averaged in depth. Both simulations show good compliance with analytical solutions.Discussion and Conclusions. Analytical solutions were found by linearization of the equations, which obviously has its limitations. A distinction is made between two types of nonlinear effects — nonlinearities caused by higher-order terms in the equations of motion, i.e. terms of advective acceleration and friction, and nonlinear effects caused by geometric nonlinearities, this is due, for example, to different water depths and reservoir widths, which will be important when modelling a real sea.

Seawater intrusion assessment along the Volturno River (Italy) via numerical modeling and spectral analysis

Surface and groundwater salinization are becoming a significant challenge to inland water quality, negatively affecting people and ecosystems in coastal areas. Even if rivers provide critical pathways for seawater intrusion, this salinization phenomenon has received relatively little attention compared to other salinization mechanisms. To assess the distribution of salinity along the final reach of the Volturno River (Italy), an entire hydrologic year was modeled using the HEC-RAS software. The model was fed with high resolution time-series measurements (time interval of 10 min) of water surface elevations at both river mouth and Cancello Arnone (a hydrometric station located 13 km inland). Field observations and remote sensed data were used to perform the hydrodynamic analysis. The model showed good performance indicators (R2 = 0.878, NSE = 0.870, and MAE = 0.037 m) and well caught hydrometric variation over the simulation period. The tidal component was affected by dissipation moving upstream and showed the capability to shape the salinity profile during dry periods. Whereas during wet periods, even if a strong tidal component is present, the profile is totally regulated by the river discharge. The analysis of the salinity distribution, modelled via the Water Quality module, revealed the massive contribution of the river discharge in limiting seawater intrusion. A correlation between intrusion events and hydrometric stages was established over twenty years (2002–2022), showing a consistent trend between intrusion occurrence and the surface water storage anomaly in the lower Volturno River calculated by Global Land Data Assimilation System (GLDAS) model. Although the 1D approach here used may lead to uncertainties in the reproduction of the involved hydrodynamic and salinization processes, the results are useful for the understanding of seawater intrusion in rivers, and may be utilized to study seawater intrusion in aquifers.

Understanding the impact of hydrodynamics on coastal erosion in Latin America: a systematic review

Coastal zones in Latin America support a significant regional population and are vital for providing essential ecosystem services that underpin crucial socio economic activities. However, these zones face pressing challenges, with coastal erosion being a prominent concern. Coastal erosion not only jeopardizes coastal stability but also leads to occasional loss of natural habitats. This is particularly worrisome for sandy beaches due to the consistent shoreline retreat in specific regions. Short term adverse effects of coastal erosion are often attributed to human activities. Nonetheless, the influence of hydrodynamic processes, intensified by extreme events, is gaining prominence. This is due to the combined impact of tides, waves, currents, and other factors, resulting in accelerated shoreline retreat and significant losses of infrastructure and beach areas across Latin America. This article conducts a comprehensive analysis of case studies in Latin America related to coastal erosion due to hydrodynamic processes. Employing a systematic review approach, data is extracted from Scopus and Web of Science databases. From an initial dataset of 701 records, 62 records meet strict eligibility criteria. Case studies present evidence of how hydrodynamic processes interact with various factors, encompassing oceanic climatic conditions, atmospheric climatic conditions, anthropogenic influences, geomorphological and bathymetric characteristics, geological and tectonic factors, and climate change related aspects. These interactions have an immediate and significant impact on sandy beaches, emphasizing the necessity of comprehensively addressing these linkages when analyzing shoreline changes. This approach aids in identifying key erosion mechanisms and developing effective mitigation measures. Furthermore, the article provides a concise overview of data sources, tools, and methodologies identified in the case studies, spanning from field investigations to the utilization of geographic information systems and numerical models. Underscores the crucial role of international academic collaboration in coastal erosion research, facilitating the adoption of innovative methodologies from other regions, potentially offering a more comprehensive perspective in the formulation of mitigation and adaptation strategies. Finally, potential areas for future research in Latin America are explored, including the assessment of extreme event variability and its impacts on local and regional hydrodynamic processes. This aspect holds critical importance in steering future research towards scenarios that encompass economic and social considerations.

A Review Article: Electro-Spinning Thin Film Nano-Spun Fibers

Abstract: Electrospinning is an electron – hydrodynamic process which is gainful and flexible method. Electrospinning forms fibers in 100 NM ranges. Electrospinning mainly composed of 3 main components. High voltage, Spinners and Target collector plate. It is versatile and viable technique for ultra-thin fibers generation. Electrospinning is mainly because there is an increase in surface area compare to volume as particle get smaller. Nanotechnology accomplished most attraction by researcher a nanomaterial exhibit novel and significantly improve properties in terms of physical, chemical, biological, mechanical properties produced of electro spun nanofiber and they can be modified accordingly. Nanotechnology is a budding technology that has been identified as a vital scientific and commercial venture with global economic benefits.

Herbaceous angiosperms, pteridophytes and shrubs cocktail for rapid ground cover for soil and water bioengineering in the Caribbean

Among the Nature-based Solutions currently spreading worldwide, soil and water bioengineering techniques, are used to stabilize hill slopes, earth embankment, and riverbanks. They consist in the use of living plants, sometimes coupled with dead materials, to control erosion and restore ecosystems.These approaches remain to be adapted to Neotropics and particularly to the Caribbean Islands biodiversity hotspot. The success of soil and water bioengineering designs depends on the selection of suitable native plant species and considering the hydrodynamic and geotechnical processes. In the Caribbean, data are available concerning woody species but are still lacking for the other constitutive components of riparian plant communities. The objective of this study was to identify the riparian forest understory species best suited for use in SWBE at their establishment phase. In a three-month ex situ experiment, we measured the survival rate, biomass production and root growth of propagules (cuttings and bulbils) of eleven native Caribbean species (5 herbs, 4 pteridophytes, 2 shrubs) occurring naturally in a variety of riparian environments. All the herb and shrub species studied displayed growth vigour adequate for a successful inclusion in soil and water bioengineering techniques. Among herbs, Commelina diffusa, Hymenachne amplexicaulis and Sphagneticola trilobata performed the best. Gynerium sagittatum and Dieffenbachia seguine, despite their slower growth and root development, remain suitable. Regarding the two shrubs, Ludwigia octovalvis gave better results than Clidemia hirta. Among the pteridophytes, Adiantum latifolium, Thelypteris reticulata and particularly Lycopodium cernuum appeared poorly suited to soil and water bioengineering. Acrostichum danaeifolium was the best-performing pteridophyte. These first experimental results focusing on the propagation and establishment of native herbs, pteridophytes and shrubs, allowed to identify a diversity of species of interest as cuttings for soil and water bioengineering and practical clues for their use in the Neotropics.

Enhancement of physicochemical stability and reduction in enzyme and microbial activity of apple juice by hydrodynamic cavitation processing

Conventional thermally processed apple juices are nutritionally depleted because the heat sensitivity degrades the bioactive compounds that comprise them. This study proposed a non-thermal technique, hydrodynamic cavitation (HC), to preserve the nutritional content and prevent the loss of bioactive components in apple juice. In addition, the effect of hydrodynamic cavitation on the physicochemical, nutrition, and enzyme inactivation of freshly expressed apple juice has been studied. The design expert software has been used for process optimization, while fuzzy logic was applied for sensory. Hydrodynamic cavitation has been used on freshly extracted apple juice with inlet pressure in the range of (34.47–103.421 kPa) for a treatment time of (0–30 min). The apple juice was treated thermally at 90 °C for 2.5 min to compare the cavitation results. The settling of particles in the cavitation sample was 7%, which was lower than the heat-treated sample (10%) and untreated control sample (39%) and had a noticeable effect on the cloud value and stability of the apple juice. The HC treatment reduces the particle size of fresh apple juice from 8934.09 nm to 1112 nm, resulting in a homogenizing effect, a decrease in viscosity, and improved juice stability. Hydrodynamic cavitation reduced the antioxidant activity from 0.4987 mg GAE mL−1 (control) to 0.3951 mg GAE mL−1 yet retained better activity than the heat-treated apple juice (0.3489 ± 0.34 mg GAE mL−1) with microbial log reduction of 0.9 at 103.42 kPa treated for 30 min. After 15 days of storage at 4 °C, HC-treated juice had higher quality features and nutrient retention than heat-treated apple juice.

Shoreline response to sea-level rise according to equilibrium beach profiles

Shoreline position is a key parameter of a beach state, often used as a descriptor of the response of the system to changes in external forcing, such as sea-level rise. Changes in shoreline position are the result of coupled hydrodynamic and morphodynamic processes happening in the nearshore and acting at different temporal scales. Due to this complexity, methodologies aimed at reproducing shoreline evolution at decadal time scale require many simplifications. Simpler methods usually consider an equilibrium beach profile whose shape depends only on beach morphology, and whose location varies depending on incoming forcing. Here, we derive a general equation for shoreline evolution using equilibrium beach profiles. We particularize it based on several common assumptions, and evaluate changes on shoreline position caused by sea-level rise, combined with simultaneous wave and high-frequency sea-level forcing. We compare our model against other analytical equilibrium beach profile-based models and with a dynamic model explicitly computing sediment transport. Results indicate that: (i) it is necessary to consider the area of the emerged beach subject to marine forcing rather than focusing only on the submerged part, (ii) the rates of shoreline recession may change for narrow beaches, defined as those for which marine forcings act onto all of their aerial surface, and (iii) Bruun’s Rule can describe beach shoreline evolution, but the uncertainty in selecting the landward boundary of the active profile entails a huge uncertainty in the magnitude of shoreline evolution. This problematic uncertainty can be drastically reduced if instantaneous forcing conditions are used instead of the arbitrary emerged/submerged active profile boundaries typically defined by only one statistic parameter of extreme conditions.

The lower Barra Velha formation (Aptian) in the Atapu field, Santos basin: Geological model for a pre-salt succession

The characterization of facies, microfacies and facies successions allowed to develop a conceptual geological model for the lower succession of the Barra Velha Formation in the Atapu field, Aptian of the Santos Basin. The obtained data and interpretations were based on the detailed description (scale 1:10) of ca. 90 m of two almost continuous well-cores and petrographic analysis. The facies were defined based on their primary depositional attributes, which are well recognized despite diagenetic modifications. Lutites, microbialites, tufa-rocks, calcirudites constitute the main recognized facies. The clastic lutites recorded transport and deposition of terrigenous and intraformational clasts by hydrodynamic and gravitational processes in low energy and shallow lacustrine environment. Microbialites and tufa-rocks record in situ carbonate deposition in alkaline saturated waters. Injectites, diastasis cracks, loop bedding, slump folds, many of the normal and listric faults and fractures are syn-depositional structures interpreted as primarily induced by tectonics. Facies changes allow to divide the succession in three stratigraphic intervals. Lutites predominates in intervals 1 and 3 whereas tufa-rocks constitute the interval 2. In the lower part of interval 1 labile fresh siliciclastic components and tractive and gravitational structures are abundant, indicating dry climate but with sporadic rainfall during a period of relative high water level of the lake. The upward decreasing of siliciclastic fragments, the appearance of coarse microbialite and a fish mortality level in the upper part of interval 1, mark the transition to the tufa-rocks of interval 2. These latter features denote a relative dryer climate and higher alkalinity waters, and a low water level of the lake. The interval 3 lutites cover abruptly the tufa-rocks recording the drowning of the succession. This may be related to renewed rifting or to the beginning of the basin thermal subsidence.

Exact Analysis of Unsteady Solute Dispersion in Blood Flow: A Theoretical Study

The diameter of an artery can narrow due to atherosclerosis or stenosis, making it challenging to resolve solute dispersion issues as blood flows via a stenosed artery. The stenosis occurrence restricted drug dispersion and blood flow. This research introduces the establishment of a mathematical model in examining the unsteady dispersion with respect to the solute in overlapping stenosis arteries depicting blood as a Herschel-Bulkley (H-B) fluid model. Note that fluid velocity was obtained by analytically solving the governing and constitutive equations. The transport equation has been solved by employing a generalised dispersion model (GDM), in which the dispersion process is described. Accordingly, yield stress, stenosis height, slug input of solute length, as well as a rise in the power-law index have improved the peak with regard to the mean concentration and solute concentration. The maximum mean concentration yielded the effective dose for therapeutic concentration. In conclusion, this study is relevant to disease arteries, coagulating hemodynamics and may help physiologists in furnishing a more refined understanding of diffusion processes in cardiovascular hydrodynamics. An interesting application related to the present study is the transportation of drugs in the arterial blood flow.

Effect of hydrodynamic cavitation processing on orange juice physicochemical and nutritional properties

Effect of hydrodynamic cavitation (HC) processing on pH, °brix, separation index, viscosity and color properties, retention of nutritional bioactive compounds (Vitamin-C, total phenolics, and antioxidant), and inactivation of enzyme pectin methyl esterase (PME) in freshly expressed juice from Brazilian oranges was investigated. HC at 4 bar pressures with a treatment time of 0, 10, 20, 30, 40, 50, 60, and 90 min at low temperatures (42 °C) were studied. There was no significant change in the values of pH, and TSS was noted in HC-treated juices. Further decreased flow behavior index while increased values of flow consistency index were recorded for the juice treated with HC showing a significant physical modification of the juice. Degradation and loss in vitamin C and total phenolics were observed when juices were HC-treated for a longer time. Therefore, it was concluded that HC could be used as a non-thermal method for improving the stability and physicochemical properties of Brazilian orange juice.

Expressive fluxes over Amazon floodplain revealed by 2D hydrodynamic modelling

Water fluxes in the Amazon River floodplain affect hydrodynamic and ecological processes from local to global scales, but they remain poorly understood due to difficult accessibility and limited data. We characterized the hydrodynamics of eight floodplain units of the central Amazon River (40000 km2) using the 2D hydraulic model HEC-RAS. High resolution modelling (∼400 m) improved the representation of river and floodplain discharge, water surface elevation (77 cm accuracy) and flood extent (∼80% - high water period, ∼52% - low water period) compared to past modelling studies. Our results show that floodplain flows during floods are very intense with upstream inflow and downstream outflow of the floodplain units. These gross flows are much larger than the net flows, with values of up to 20% of the Amazon River discharge and residence time around 6 days during floods (several months during low water period). Water extent did not show strong interannual variability during floods as the volume stored in the floodplain did, possibly due to topographic constraints. Significant hysteresis in flood extent and volume, and active and storage zones on the floodplain highlight the complexity of floodplain hydrodynamics. Extreme floods strongly impacted the onset and duration of the flood by up to one month and, consequently on duration of high water renewal period with the river. Our characterization is important to assess the effects of extreme floods on riverine communities, understand nutrient and sediment variations in the floodplain, and characterize the export of water, sediment, and carbon flux to the ocean from the world's largest hydrological system.

On Improving Sheet Metal Formability in Hydrodynamic Deep Drawing Process through a Solid‐Oil‐Type Mineral Grease Pressure Medium

In this research, the improvement in sheet metal formability obtained through the utilization of a mineral grease in solid‐oil‐type (SMG) pressure medium in the hydrodynamic deep drawing process assisted by radial pressure is investigated by experiments and finite‐element method (FEM) simulations on flat‐bottom cups realized with pure copper and DIN 1.0338 steel. To determine the process parameters ranges, an FEM model is developed in ABAQUS/Explicit and validated against experimental results. Afterward, experiments are carried out using two pressure mediums with different viscosities, i.e., water and SMG. Considering the results relevant for both sheet materials, the SMG medium allows an average reduction of the sheet metal thinning of 15% and 10% on the corner edges while also granting a negligible thickness variation on the cup walls. In contrast, the higher viscosity of the SMG, in comparison to the water medium, also results in an average 16% increase in the forming force when compared to the water pressure medium.

A comparative study on source of water masses and nutrient supply in Zhanjiang Bay during the normal summer, rainstorm, and typhoon periods: Insights from dual water isotopes

Typhoons and rainstorms (rainfall >250 mm day−1) are extreme weather events that seriously impact coastal oceanography and biogeochemical cycles. However, changes in the mixing of water masses and nutrient supply induced by typhoons and rainstorms can hardly be identified and quantified by traditional methods owing to the complex hydrological conditions in coastal waters. In this study, we analysed a comparative data set of dual water isotopes (δD and δ18O), hydrological parameters, nutrients, and chlorophyll-a from three periods (normal summer, rainstorm, and typhoon periods) in Zhanjiang Bay, a typical semi-enclosed mariculture bay in South China, to address this issue. The results revealed a significant increase in contributions from freshwater during rainstorms and typhoons. Correspondingly, nutrient supplies from freshwater during these periods remarkably increased compared to the normal summer, indicating that heavy rainfall can transport substantial amounts of terrestrial nutrients into the bay. Furthermore, disparities in hydrodynamic processes between typhoon and rainstorm periods were notable due to inconsistencies in freshwater diffusion paths. During rainstorms, freshwater primarily diffuses towards the outer bay in the upper layer due to strong stratification and cannot form an ocean front. However, under intense external forces caused by the typhoon, high-salinity water intruded into the bay, and enhancement of vertical mixing disrupted stratification. The massive influx of freshwater column during the typhoon mixed with higher salinity seawater column in the bay led to the formation of an ocean front, which could retain contaminants. This study suggests that although both rainstorms and typhoons can discharge large quantities of terrestrial nutrients into Zhanjiang Bay, the front formed during the typhoon period impedes the contaminant transportation to open sea thereby deteriorating water quality and affecting mariculture activities within the bay.

ИССЛЕДОВАНИЯ ГАЗОДИНАМИЧЕСКИХ И ГИДРОДИНАМИЧЕСКИХ ПРОЦЕССОВ В ПОЛОСТЯХ И КАНАЛАХ ВАКУУМНЫХ ЗАХВАТНЫХ УСТРОЙСТВ

The article discusses the results of studies of gas-dynamic and hydrodynamic processes in cavities and channels of vacuum gripping devices operating in air, water and mixed media. Transient processes were obtained that occur in the cavities of the gripping devices from the moment the vacuum generator is powered up to the moment of the steady-state vacuum level.