Outlet Zone Research Articles

Assessing Seasonal Variations in Reservoir Water Quality: Implications for Eutrophication and Pollution Management

Surface water is a strategic freshwater reserve that meets the needs of households, agriculture, livestock, industry, and research. Surface water quality is affected by anthropogenic activities and seasonal variations, which can pose ecological risks. This study aimed to assess the water quality of the Darma Reservoir, the status of water quality and trophic levels, and trends in water quality changes in the rainy and dry seasons. The study was conducted for one year, from October 2023 to September 2024, covering the rainy and dry seasons. Sampling was carried out at eight stations spread across three zones of the Darma Reservoir, namely the inlet zone, utilization zone, and outlet zone. Water quality parameters were tested using PCA, the water sample measurements were compared with water quality standards (PP/22/2021), and the Regulation of the Minister of State for the Environment number 28 of 2009 was analyzed using the STORET index. The results of the study showed differences in water quality characteristics between seasons, where the concentration of Total Nitrogen (TN) showed an increase in the rainy season, while the concentration of Total Phosphate (TP) was higher in the dry season.

Examining hydro-morphological modulations in proximity to a drain's estuarine outlet, case study: Kitchener Drain, Northern Coast of Egypt

In recent years, the Kitchener Drain has been affected by littoral erosion and sedimentation at the estuary where its discharge enters the Mediterranean Sea. Several measures have been taken to mitigate the impact of these problems. From 1993 to 2007, four stages of hard protection work were finished, including the construction of groins and detached breakwaters along the drain's eastern and western shores. Work on these projects began in 1992. At the drain outlet, dredging works are still proceeding. Nevertheless, shoreline instability continues even after these efforts. The Coastal Modelling System (CMS) was used to figure out what effect the ongoing hard work had on the erosion and accretion hot spot near the drain's output. The CMS-flow and CMS-wave steering modules are part of the CMS, a two-dimensional model of hydrodynamic circulation. To begin mitigating this effect, we ran the simulation beginning in 2012 and experimented with different calibration settings. After the calibration phase, the research area was subsequently simulated for five years. This study aims to assess the current state of affairs concerning the stabilization of the outflow sedimentation process and the erosion that is taking place on the eastern and western sides. In addition to that, we offered alternate structural modulation scenarios that incorporate both hard and soft structures. We looked at plenty of different possibilities. The scenario with the 600-meter-long jetty and sand nourishment was the most similar to the original coastal characteristics. Regarding a sediment reduction to ‐5706.99 m3 from ‐15321.70 m3 (at benchmark) computed at the outlet zone, this scenario was the most similar to the shoreline's initial appearance. Reducing sediment from ‐133433 m3 (at benchmark) to ‐114512 m3 was also achieved on the western side. Despite this, it was determined that the stability of the coastline would be influenced subtly by this circumstance.

Accurate Analysis of Stand-up Time Rock Collapse When Inlet Tunnel Excavation is Carried out in there are Cracked and Broken Rock Formations and a Poorly Silty-clay Soil Profile

The condition of the rock formation and the poor stability of the type of soil mass (problematic soil) in the tunnel excavation route greatly influence the achievement of the collapse (stand-up time) that will occur. The thickness of the overburden pressure above the tunnel opening is often difficult to meet, so in the inlet zone as well as in the out-let zone, slope collapse often occurs and disrupts the work implementation schedule. On the slope of the inlet excavation location, there are also silt formations with outcroppings. Rocks from small to large sizes and there are even rock masses that are cracked so that the quality or strength of the rock is unstable when exposed to the equipment used when tunnel excavation work is carried out. This research method was carried out using an approach that corresponds to the Rock Quality Designation (RQD) value with the Rock Mass Rating (RMR) value which will provide a classification of rock classes and excavation methods. The data used in this research is rock data at the tunnel inlet of the Rukoh Dam Steering Building. From the RQD and RMR data and soil physical properties obtained in this research, analysis was carried out using the empirical approach introduced by Bieniawski. The results obtained from the in-situ test drilling work, the results of which were stored in the core box at the tunnel inlet, obtained an RQD value equal to 32.5% and an RMR value equal to 15. The RMR value shows that the rock at the tunnel inlet falls into the very category poor. With a tunnel opening as wide as 6.60 M, the stand-up time at the tunnel in-let is less than 30 minutes.

Energy loss evaluation of a radial inflow turbine for organic Rankine cycle application using hierarchical entropy production method

To evaluate the location and main sources of energy loss in radial inflow turbines for organic Rankine cycle application, this study proposed a hierarchical entropy production method, which is superior to the traditional pressure drop method. The method includes three levels: local entropy production, split of turbine total entropy production, and split of component entropy production. The energy loss of the radial inflow turbine under design condition and different pressure ratios is presented. The results indicate that the high-entropy production zone is primarily located at the stator trailing edge and the rotor tip clearance. The proportion of turbulent entropy production and wall entropy production in the total energy loss of the turbine is about 77% and 20%, respectively. Among the components of the radial inflow turbine, the energy loss of the rotor and diffuser is the highest, accounting for 71.9% and 13.6% of the total entropy production of the turbine, respectively. However, the stator and rotor have higher volume average entropy generation rate and area average entropy generation rate. The high-entropy production region is mainly located in the stator outlet zone and the rotor tip zone. When the pressure ratio increases from 3 to 5, the turbine efficiency decreases by 13.44%. The pressure ratio has a significant effect on the turbulent entropy production of the rotor. This method can provide insight into the energy loss characteristics of radial inflow turbines for organic Rankine cycle applications.

Disturbed fluid flow reinforces endothelial tractions and intercellular stresses

Disturbed fluid flow is well understood to have significant ramifications on endothelial function, but the impact disturbed flow has on endothelial biomechanics is not well understood. In this study, we measured tractions, intercellular stresses, and cell velocity of endothelial cells exposed to disturbed flow using a custom-fabricated flow chamber. Our flow chamber exposed cells to disturbed fluid flow within the following spatial zones: zone 1 (inlet; length 0.676–2.027 cm): 0.0037 ± 0.0001 Pa; zone 2 (middle; length 2.027–3.716 cm): 0.0059 ± 0.0005 Pa; and zone 3 (outlet; length 3.716–5.405 cm): 0.0051 ± 0.0025 Pa. Tractions and intercellular stresses were observed to be highest in the middle of the chamber (zone 2) and lowest at the chamber outlet (zone 3), while cell velocity was highest near the chamber inlet (zone 1), and lowest near the middle of the chamber (zone 2). Our findings suggest endothelial biomechanical response to disturbed fluid flow to be dependent on not only shear stress magnitude, but the spatial shear stress gradient as well. We believe our results will be useful to a host of fields including endothelial cell biology, the cardiovascular field, and cellular biomechanics in general.

Remote sensing estimation of water transparency for Saguling Dam in the past decade (2013-2022) based on Landsat 8

Water transparency (i.e., Secchi disk depth (SDD) reflects light transmission capacity of a water body and influences growth of aquatic plants, aquatic organisms, and primary productivity. In this study, using remote sensing reflectance (Landsat 8) and SDD datasets, we predicted the water transparency in Saguling Dam for the first time. The results indicated that the models in the visible (Band 1, Band 2, and Band 3) combined with near infrared (Band 4 and Band 5) are the most robust and reliable to estimate SDD for Saguling Dam. Subsequently, multiple linear regression model was built using 125 pairs of in situ SDD results and concurrent with Landsat images during the last decade (i.e., 2013-2022). The models were validated with an independent dataset of 33 SDD measurement. The in situ remote sensing model compared well with the in situ SDD measurement where determinant coefficient (adjusted R2) and root mean square error (RMSE) ranging from 0.35 - 0.94 and 0.3 - 1.4 m, respectively. Finally, the model was applied to Landsat 8 images acquired between 2013-2022 to elucidate the spatial distribution of SDD in Saguling Dam for each year (i.e. temporal variations) with water area around 33.7 km2. The estimation results indicated that water transparency values in the inlet and outlet zone have relatively low SDD, with SDD value ranging from 0.019 – 1.01 m and 0.24 – 1.04 m, respectively. Furthermore, based on the National Water Quality Standards (i.e., Indonesia Government Regulations No. 22 year 2021/ Peraturan Pemerintah No. 22 Tahun 2021), the estimation of spatial SDD results indicated that > 99% of Saguling Dam water bodies were classified as Class IV (i.e., could be only used for irrigation). This study provides the first comprehensive remote sensing model for Saguling Dam and can provide essential information for local water quality conservation.

Characterization of seepage in an earthfill dam by the integration of geophysical surveys and geotechnical data

Seepage is a common phenomenon in earthfill dams, and one that typically warrants episodic assessment and monitoring by regulatory agencies. Geophysical surveys provide a convenient, cost-effective, and convenient means for assessing seepage, but only if they are applied in effective combinations and if the data are analyzed properly. In the present study, a self-potential survey of streaming potential and a 2D electrical resistivity tomography survey were notably successful in detecting seepage under the embankment of the nearly 90-year-old Standing Rock Dam No. 1 in South Dakota, USA. Self-potential (SP) measurements show a localized negative anomaly of up to 27 mV on the upstream side of the dam, which we interpret to be the inlet or recharge zone for seepage, and a positive anomaly of up to 20 mV on the downstream side, which we interpret to be the outlet or discharge zone. The spatial correlation between our resistivity models, SP data, and topography was excellent. Water-saturated, conductive deposits in the dam's embankment match a negative SP amplitude in the inlet or recharge area. Similarly, water-saturated electrically conductive sediments are characterized by a positive SP amplitude in the discharge area where surface seepage occurs in a topographic low. Six years of water-level measurements in the existing piezometers interpreted relative to the properties and spatial distribution of coarser-grained alluvium (sand and gravel) underneath the dam's embankment fill, suggest that most seepage occurs under the dam. Our approach to assessing seepage in this project should be widely applicable to earthfill dams worldwide, and our modeled results constitute a valuable case study.

A Multi-Parameter-Coupled Mixed Lubrication Model for Rolling Interface Analysis: An Investigation on Interfacial Oil Pressure and Oil Film Thickness

Utilizing the average Reynolds equation, lubrication friction theory, metal rolling deformation theory, and temperature energy theory, a multi-parameter-coupling mixed lubrication model considering the influence of surface roughness with Gaussian distribution characteristics under rolling conditions was established. The results show that the stress distribution of the lubricating oil at the rolling interface conforms to the typical characteristics of line contact stress distribution. The oil film pressure does not increase significantly with the increase in the reduction ratio. A second peak pressure appears before the outlet. The second peak pressure reaches its maximum when ε = 0.2. The rolling speed has little effect on oil film pressure, but greatly affects oil film thickness. The influence of rolling speed mainly occurs in the outlet zone and at the second peak pressure location. The oil film thickness increases with rolling speed. During rolling, the temperature rise in the rolls exhibits two peak values. The first peak appears near the neutral point, and the second peak appears near the outlet, which is also where the second peak pressure is located. The influence of temperature will reduce the peak stress on the rolls. The overall stress on the rolls will also decrease.

Simulation of natural convection in a solar collector

The process of natural convection in a flat solar collector, which was designed by the authors, was mathematically modeled using experimental data. Stones were used as storage means. The inclined collector is expressed as a two-dimensional plate for modeling. The initial and boundary conditions were formulated. It was assumed that the flow in this region is laminar. To simulate the flow of natural air convection, a system of non-stationary partial differential equations was chosen based on the laws of conservation of mass, momentum and energy in the Boussinesq approximation. The equations were solved in a dimensionless form using the finite difference method and an explicit scheme. The picture of the temperature fields and the appearance of convection was obtained on the basis of experimental temperature data in the inlet and outlet zones of the collector, as well as on the surface of the heat accumulator during the day. To evaluate the effectiveness of the resulting model an average approximation error (approximation) of 7.7% was established. The results obtained in specific values of the Grashof and Prandtl numbers are presented in the form of graphs.

Experimental investigation of bubble size evolution released from a fine bubble ejector

AbstractThe effects of gas flow rate, liquid flow rate, and liquid properties on the bubble size evolution at the outlet zone of an ejector have been investigated systemically. The liquid properties, including surface tension and viscosity, were changed by adding glycerol, ethanol, or Carbopol 2020 into tap water. It was found that increasing the liquid flow rate is beneficial for producing smaller bubbles with a narrower size distribution in the ejector, while the gas flow rate investigated here shows less influence on the generated fine bubble diameter. An intense bubble coalescence phenomenon, which has a negative effect on mass transfer, was first observed at the small outlet zone of the ejector by exploring the bubble size evolution along the axial height. It was found that the mean diameter of the fine bubbles could increase by 48% ~ 90% when they rose only 25 cm from the ejector outlet, and the bubble coalescence could be effectively suppressed by adding a small amount of glycerol to water. The bubble diameter could be reduced by 32% ~ 43% by using a 2 wt.% glycerol solution under the experimental conditions. A comparative study with tap water, glycerol solution, Carbopol solution, and ethanol solution was taken, and the underlying mechanism of reducing the generated bubble size by changing the liquid properties was revealed.

The Analysis of Mercury Concentrations of Water in Gold Mining Environment at Poboya, East Palu Subdistrict, Palu, Central Sulawesi Province

Gold mining activities influence the environment, mainly the aquatic environment, due to the heavy metal and mercury detected in settling pond and river waters. Based on laboratory analysis, it is known that Mercury concentrations in settling pond water of inlet, transition, and outlet zones respectively are 0.075 mg/L, 0.042 mg/L, and 0.027 mg/L. These are shown that mercury concentration in water was not passed Government Regulation of the Minister of Environment No. 202 the year 2004 about quality standards of liquid waste, which said that the standard is 0.005 mg/L. The Heavy metal concentrations, especially mercury in river water at 1, 2, 3, 4, and 5 stations respectively, are 0.004 mg/L, 0.009 mg/L, 0.050 mg/L, and 0.006 mg/L, which do not meet the government regulation of water quality standard 0.001 mg/L.

Investigation of the complex 3D flow structure within a selective catalytic reduction (SCR) reactor of a coal-fired power plant

A selective catalytic reduction (SCR) reactor is commonly used to remove nitrogen oxides (NOx) from coal-fired boilers. Uniformity of the flow passing through the catalyst layer is important for increasing denitrification (de-NOx) efficiency. In order to examine flow uniformity, this study conducted an experimental and numerical analysis of the complex internal flow within a realistic SCR model. Magnetic resonance velocimetry (MRV) was utilized to obtain non-invasive measurements of three-dimensional three-component average velocity and validate Reynolds-averaged Navier-Stokes (RANS) numerical simulations. The computational results showed similar overall flow structure compared with the MRV results. Parameters representing flow quality such as relative standard deviation (RSD) and recirculation zone strength (RZS) were calculated by integrating the flow field. These parameters have the largest value after the straightener area and decrease towards the catalyst reactor, and are not significantly affected by Reynolds number upstream of the catalyst layer. The recirculation zone size was analyzed using spanwise uniformity and skewness indicators. As the recirculation zone induces biased flow, the non-reacted NOx concentration was more prominent in the outlet zone opposite of the recirculating area in the corresponding actual on-site SCR reactor. Based on this finding, a meaningful correlation between flow maldistribution and de-NOx reaction could be deduced.

What is the best procedure for determining removal rate coefficients in horizontal flow treatment wetlands: influent and effluent concentrations or longitudinal concentration profiles?

First-order removal rate coefficients (k) are used in predictive equations for estimating effluent concentrations from horizontal flow (HF) wetlands. Due to limited resources, influent and effluent concentration data from existing systems are frequently used in the estimation of k values from operating systems, but another choice is to use concentration data along the longitudinal profile of the HF wetland. Based on a dataset with 41 HF wetlands/studies obtained from a literature survey, with chemical oxygen demand (COD) measurements at different sampling points, volumetric (kV) and areal (kA) removal rate coefficients for the Tanks-In-Series (TIS) model have been obtained using the two estimation methods. In general, removal rate coefficients derived from longitudinal profiles of concentrations were higher than those obtained by using data from influent and effluent concentrations, reflecting the fact that constituent removal is mostly accomplished before the wastewater reaches the outlet zone. Deriving coefficients from longitudinal profiles is more comprehensive, providing a better explanation of the internal removal taking place in the treatment wetland. However, the more widely used approach of calculating kV and kA from influent/effluent concentrations may lead to a safer design of horizontal flow wetlands, because of underestimation of the actual removal rate coefficients.

Energy-Conserved Hydrodynamic Lubricated Components with Wall Slippage

The hydrodynamic thrust slider and journal bearings as well as hydrodynamic lubricated gears with the merit of energy conservation by the wall slippage are reviewed. The principle for designing these hydrodynamic contacts is to artificially set the wall slippage on the stationary surface in the hydrodynamic inlet zone. To design the wall slippage on the moving surface in the hydrodynamic outlet zone can also give additional benefits. The technical merits of these mechanical components are the improved load-carrying capacity and the lowed friction coefficient, i.e., the energy conservation due to the wall slippage. Owing to the designed wall slippage, the carried load of the hydrodynamic step bearing can be increased by 200%~400% while its friction coefficient can be reduced by 50%~85%, and the load-carrying capacity of the hydrodynamic journal bearing can be increased by nearly 100% while at the same time, its friction coefficient can be reduced by more than 60%. For hydrodynamic lubricated gear contacts, by covering ultrahydrophobic or oilphobic coatings on the slower moving surface, the friction coefficient can be approaching to vanishing and the contact load-carrying capacity can be increased very significantly for large slide-roll ratios under medium or heavy loads.

Multiscale analysis and numerical simulation of hydrodynamic inclined fixed pad thrust bearing with ultra low surface separation

In the hydrodynamic inclined fixed pad thrust bearing, when the surface separation is ultra low, there will be the special hydrodynamic mode where in the inlet zone occur both the adsorbed boundary layer flows and the intermediate continuum fluid flow i.e. the multiscale flow and in the outlet zone only occurs the physical adsorbed boundary layer flow. This new mode of hydrodynamic bearing has not been addressed before. Here, we present the corresponding multiscale hydrodynamic analysis for this bearing. The inlet zone flow is described by the closed-form explicit multiscale flow equations. The outlet zone flow is described by the nanoscale flow equation. First, the analytical derivations for the pressure distribution and carried load of the bearing were feasibly made by making a reasonable assumption. Then, full numerical solutions to the bearing were obtained to verify the analytical solution. It was found that there are significant differences between the analytically calculated pressure distribution and the numerically solved pressure distribution for the same operating condition; however for the studied different fluid-bearing surface interactions, when the surface separation is relatively large, the analytically derived load equation can be used to calculate the carried load of the bearing. Numerical solutions clearly show that stronger the fluid-bearing surface interaction, higher the generated hydrodynamic pressure in the bearing, and larger the carried load of the bearing. The study not only provides the mathematical tools for studying the bearing but also gives the indication of the strong adsorbed boundary layer effect in this bearing.

MULTISCALE HYDRODYNAMICS IN INCLINED FIXED PAD THRUST SLIDER BEARING WITH INHOMOGENEOUS SURFACES

For two different and inhomogeneous surfaces, the flow equations for multiscale hydrodynamics involving the boundary layer flows are different from those for two identical and homogenous surfaces. The analysis is presented for the hydrodynamic inclined fixed pad thrust slider bearing with two different and inhomogenous surfaces with low bearing clearances, where both the adsorbed boundary layer flows and the intermediate continuum fluid flow should be considered. Based on the governing equations, the pressure and carried load of the bearing were derived. The calculation results show the performance of the studied bearing different from the bearing with homogeneous surfaces. It was found that by taking the stationary surface in the inlet zone as hydrophobic (or oilphobic) while that in the outlet zone as hydrophilic (or oilphilic), the load-carrying capacity of the bearing can be significantly improved if the bearing clearance is such that the multiscale flow regime occurs and the tilting angle of the bearing is sufficiently small, e.g., no more than 1 × 10<sup>-4</sup> rad.

A microscale system for in situ investigation of immobilized microalgal cell resistance against liquid flow in the early inoculation stage.

In attached microalgae cultivation systems, cell detachment due to fluid hydrodynamic flow is not a subject matter that is commonly looked into. However, this phenomenon is of great relevance to optimizing the operating parameters of algae cultivation and feasible reactor design. Hence, this current work miniaturizes traditional benchtop assays into a microfluidic platform to study the cell detachment of green microalgae, Chlorella vulgaris, from porous substrates during its early cultivation stage under precisely controlled conditions. As revealed by time lapse microscopy, an increase in bulk flow velocity facilitated nutrient transport but also triggered cell detachment events. At a flow rate of 1000 μL min-1 of growth medium for 120 min, the algal cell coverage was up to 5% lower than those at 5 μL min-1 and 50 μL min-1. In static seeding, the evolution of attached cell resistance toward liquid flows was dependent on hydrodynamic zones. The center zone of the microchannel was shown to be a "comfortable zone" of the attached cells to sequester nutrients effectively at lower medium flow rates but there was a profile transition where outlet zones favored cell attachment the most at higher flow rates (1.13 times higher than the center zone for 1000 μL min-1). Besides, computational fluid dynamics (CFD) simulations illustrated that the focusing band varied between cross-sections and depths, while the streamline was the least concentrated along the side walls and bottom plane of the microfluidic devices. It was intriguing to learn that cell detachment was not primarily happening along the symmetry streamline. Insight gained from this study could be further applied in the optimization of operating conditions of attached cultivation systems whilst preserving laminar flow conditions.

Analysis for Hydrodynamic Wedge-Platform Thrust Slider Bearing with Ultralow Surface Separation

For the case of ultralow surface separation, in a hydrodynamic wedge-platform thrust slider bearing, the outlet zone and a portion of the inlet zone are in boundary lubrication, while most of the inlet zone is in the multiscale lubrication contributed by both the adsorbed boundary layer and the intermediate continuum fluid film. The present paper first presents the mathematical derivations for the generated pressure and carried load of this bearing based on the governing equation for boundary lubrication and the multiscale flow equation. Then, the full numerical calculation is carried out to verify the analytical derivations. It was found that the mathematical derivations normally have considerable errors when calculating the hydrodynamic pressure distribution in the bearing, owing to introducing the equivalent parameter λ bf , e which is constant in the inlet zone; however they can be used to calculate the carried load of the bearing when the surface separation in the outlet zone is sufficiently high. The study suggests the necessity of the numerical calculation of the hydrodynamic pressure and even the carried load of this bearing. It is also shown that owing to the fluid-bearing surface interaction, the pressure and carried load of this bearing are significantly greater than those calculated from the classical hydrodynamic theory.

T‐Joint Micromixer Coupled with Deforming Diaphragm

A novel active micromixer design involving an oscillating diaphragm is proposed. A simulation study is performed to determine the effect of diaphragm length, amplitude, and frequency of the oscillating diaphragm on the mixing index. The geometry is a simple T-joint with an elongated channel for the outlet with a diaphragm on the outlet channel wall. The fluids at the inlets are similar in fluid properties with the same flow rate and diffusion constant. The mixing index saturates with increasing frequency and amplitude of oscillation for a given diaphragm length. The diaphragm's effectiveness was calculated based on the pressure difference between the diaphragm inlet and outlet zone. The effectiveness declined with an increase in the frequency of the diaphragm oscillation. An analytical expression is derived to find the effect of the frequency and amplitude of the diaphragm oscillation on the mixing index. This simple novel design may find wide applications in various industrial fields.

Secret Sharing-Based Energy-Aware and Multi-Hop Routing Protocol for IoT Based WSNs

Abstract: Modern advancements in insolent sensors, RFID, Web - based machineries, and technical requirements are made possible by the Internet of Things (IoT). Sensor nodes are often employed to collect and transmit sensed data and are thought of as intelligent devices. In addition to these inherent limitations, sensor nodes are also open to a number of security risks. In order to improve the quality of renewable energy with multi-hop information security versus malicious acts, this work provides (ESMR) protocol. There are three primary components to the suggested procedure. The network field is first divided into inlet and outlet zones depending on the placement of the nodes. Additionally, a large number of clusters are created in each zone based on the proximity of the node neighbourhood. Second, the suggested effective secret sharing mechanism is used to protect the data transfer from cluster members in each zone to the bowl node. In order to reduce routing disruption, the suggested approach examines the mathematical analysis of data connections. The work described offers a multi-hop, compact, secure data analyst solution for limited wireless communications based on the Internet of Things (WSNs). In terms of bandwidth by 38 percent, network available bandwidth by 34 percent, electricity intake by 34 percent, median end-to-end postponement by 28 percent, and high latency by 36 percent when compared to the conventional work, the experimental results of the part of the application and secure number of co routing protocol