Drainage Capability Research Articles

Simulation of flood protection using Hec Ras Modeling: A case study of the Lam Phra Phloeng river basin

The Lam Phra Phloeng reservoir, positioned within the Lam Phra Phloeng river basin and situated in Nakhon Ratchasimi province, assumes a substantial role in the realm of regional water management. During severe storms in the reservoir's upper region, excess water flows downstream, occasionally resulting in devastating floods in Pak Thongchai district, as witnessed in 2010 and 2020. Both flooding events have resulted in significant economic, social, and livelihood disruptions to the local population in the affected areas. This study pursues two primary objectives: firstly, to assess the extent of flood-prone areas across various return periods (2, 5, 10, 25, 50, 100, and 500 years); secondly, to employ Hec Ras modeling for an in-depth analysis of strategies aimed at flood prevention and mitigation within the Lam Phra Phloeng river basin. The Hec Ras modeling incorporates both 1D and 2D flow simulations. The findings reveal that the flood-prone areas, corresponding to the specified return periods, occupy 0.20%, 1.10%, 1.60%, 2.08%, 2.39%, 2.66%, and 3.17% of the total area in the Lam Phra Phloeng river basin, respectively. To safeguard against flooding and minimize its impact, a multifaceted approach is recommended, encompassing the construction of water barrier flaps, augmentation of water transmission and drainage capacity, implementation of flood alarm systems along the Lam Phra Phloeng river, installation of runoff stations, and the establishment of a comprehensive database system for flood and drought prevention. Among these measures, constructing water barrier flaps and enhancing water transmission and drainage capabilities stand out as effective strategies to protect the Lam Phra Phloeng river basin from flooding.

Research on the Application of New Polylactic Acid (PLA) Fiber Concrete Materials in Urban and Rural Flood Resistance

This paper aims to study and apply new polylactic acid (PLA) fiber concrete materials to improve urban and rural flood resistance, enhance flood control and drainage capabilities, and promote sponge city construction. Through the analysis of the characteristics, proportion optimization and performance of PLA fiber concrete in actual projects, it is found that the material has good mechanical properties, environmental adaptability, economy and environmental protection, and has important application prospects in urban and rural flood control and drainage. By adjusting the proportion, selecting the appropriate fiber type and addition amount, the flood resistance and drainage capacity of concrete can be improved. Combined with 3D printing technology and modern scientific and technological means, the application and development of PLA fiber concrete will be further promoted to achieve a win-win situation of continuous improvement of urban and rural flood resistance and environmental protection. With the support of relevant technologies and policies, PLA fiber concrete has broad application prospects in sponge city construction and urban and rural flood control and drainage, and will make important contributions to improving the level of urban and rural disaster prevention and mitigation.

Predicting Ballast Fouling Conditions with the Gaussian Mixture Model

Railroad ballast is typically comprised of only large granular particles. However, the degradation of fresh ballast and the arrival of foreign fines result in ballast fouling. Compared with fresh ballast, fouled ballast exhibits reduced resilience and compromised drainage capabilities. To optimize track performance, maintenance activities for the ballast are frequently scheduled based on the fouling severity. An accurate assessment of ballast fouling conditions can enhance maintenance efficiency and reduce costs. Over the years, while many ballast fouling evaluation methods have been developed, their widespread adoption has been hindered by system costs and implementation challenges. This study aims to address this by developing an affordable and easily implemented approach to estimating ballast fouling conditions using the Gaussian Mixture Model (GMM). Initially, images of fouled ballast are characterized by fitting the distributions of each RGB (Red, Green, Blue) channel. Subsequently, two mathematical methods, expectation-maximization and point estimation, are employed to solve the GMM parameters. These derived GMM parameters are then used to backcalculate the sample parameters, facilitating the estimation of ballast fouling conditions. The results of this study reveal a close alignment between the ballast fouling conditions backcalculated with the GMM and those quantified through laboratory sieving analysis. This study thus presents a promising path forward, using images captured from cost-effective cameras to estimate ballast fouling conditions with minimal computational expense.

Multi-Phase flow simulation for transient analysis of ballast drainage behavior and shoulder cleaning effect

This paper presents multi-phase flow simulations to analyze the transient transport of rain droplets through rail ballast and its dependence on fouling conditions and shoulder cleaning. The entire process consisting of random rain droplet injection, droplet migration through the air, falling on the ballast surface, drainage through the void spaces between ballast aggregates, and running off the ballasts are modeled. A computational fluid dynamics (CFD) model is developed, in which the volume of fluid (VOF) method and Darcy-Forchheimer's equation are employed to capture the gas–liquid mixture interface and consider fouling-induced flow resistance, respectively. The model is implemented as an interFoam solver in the OpenFOAM CFD tool. A method for determining trapped moisture inside the fouled and moderately fouled ballast layers is also presented. Parametric simulations are conducted to investigate the effect of fouling conditions, more specifically, Fouling Index (FI), Fouling Profile (FP), and shoulder cleaning on ballasts' drainage performance and time-dependent moisture accumulation and penetration. The results indicate that severe congestion in fouled ballast is responsible for higher moisture accumulation, slower penetration, and poorer drainage of ballast. Shoulder cleaning is an effective measure to reopen flow passage and restore drainage capability, in particular, for the fouled ballast.

Evaluation of Waste Ceramic Tiles, Reclaimed Asphalt Pavement and Recycle Concrete Aggregate as Pavement Sub-Base

The use of various reclaimed or recycled materials from ancient structures as a source of construction materials has become common in modern road and pavement engineering procedures due to the shortage of fresh natural aggregate supplies and rising processing prices. Waste ceramic tiles (WCT), reclaimed asphalt pavement (RAP), and recycled concrete aggregate (RCA) have all been used for a long time as aggregates in the construction of pavement. WCT, RAP, and RCA are all thoroughly analyzed in this paper, with a focus on their mechanical, environmental, and physical properties. To evaluate the load-bearing ability, drainage capabilities, and long-term durability of these substitute materials when applied as pavement sub-base, laboratory tests and performance analysis were carried out. Since different mixtures of these materials are created, the maximum California bearing ratio of 25.54% is found. By promoting the usage of recycled materials, eliminating waste, and lowering the carbon footprint associated with conventional construction processes, this initiative helps to sustainably build out transportation infrastructure.

Field experiment on a vegetation-wicking geotextile-reinforced base for a permeable sidewalk

Wicking geotextiles have proven effective in reducing water content in road bases under both saturated and unsaturated conditions, thereby increasing granular base strength and mitigating moisture-related damage to the pavement. Despite their effectiveness in paved roads, the use of wicking geotextiles in permeable road and sidewalk, particularly in areas requiring robust drainage such as sponge cities, is not well explored. In “sponge city” roads, moisture content fluctuations and subsequent damage to the structure often cause concern, and the wicking geotextile’s drainage could be a potential solution. Therefore, this study aims to investigate and quantify the effectiveness of wicking geotextiles in reducing the moisture content and improving the resilient modulus of permeable sidewalk base layers. The moisture contents of unstabilized and one-directional wicking geotextile- and two-directional wicking geotextile-stabilized bases under permeable paving bricks were monitored with an interval of 7–10 days for over a year. An analytical approach to reconstruct daily moisture content in the base layer was proposed based on the simulated rainfall saturation test. This approach further assesses the enhancements in resilient modulus due to the drainage capabilities of wicking geotextiles. The experimental results indicated that the two-directional wicking geotextile outperforms its one-directional counterpart and both wicking geotextiles outperformed the control condition in terms of drainage efficiency. By reconstructing the daily moisture content and utilizing the relative damage model, the two-directional wicking geotextile significantly improved the annual equivalent resilient modulus of the base layer under permeable paving bricks.

Large-scale in-silico analysis of CSF dynamics within the subarachnoid space of the optic nerve

BackgroundImpaired cerebrospinal fluid (CSF) dynamics is involved in the pathophysiology of neurodegenerative diseases of the central nervous system and the optic nerve (ON), including Alzheimer’s and Parkinson’s disease, as well as frontotemporal dementia. The smallness and intricate architecture of the optic nerve subarachnoid space (ONSAS) hamper accurate measurements of CSF dynamics in this space, and effects of geometrical changes due to pathophysiological processes remain unclear. The aim of this study is to investigate CSF dynamics and its response to structural alterations of the ONSAS, from first principles, with supercomputers.MethodsLarge-scale in-silico investigations were performed by means of computational fluid dynamics (CFD) analysis. High-order direct numerical simulations (DNS) have been carried out on ONSAS geometry at a resolution of 1.625 μm/pixel. Morphological changes on the ONSAS microstructure have been examined in relation to CSF pressure gradient (CSFPG) and wall strain rate, a quantitative proxy for mass transfer of solutes.ResultsA physiological flow speed of 0.5 mm/s is achieved by imposing a hydrostatic pressure gradient of 0.37–0.67 Pa/mm across the ONSAS structure. At constant volumetric rate, the relationship between pressure gradient and CSF-accessible volume is well captured by an exponential curve. The ONSAS microstructure exhibits superior mass transfer compared to other geometrical shapes considered. An ONSAS featuring no microstructure displays a threefold smaller surface area, and a 17-fold decrease in mass transfer rate. Moreover, ONSAS trabeculae seem key players in mass transfer.ConclusionsThe present analysis suggests that a pressure drop of 0.1–0.2 mmHg over 4 cm is sufficient to steadily drive CSF through the entire subarachnoid space. Despite low hydraulic resistance, great heterogeneity in flow speeds puts certain areas of the ONSAS at risk of stagnation. Alterations of the ONSAS architecture aimed at mimicking pathological conditions highlight direct relationships between CSF volume and drainage capability. Compared to the morphological manipulations considered herein, the original ONSAS architecture seems optimized towards providing maximum mass transfer across a wide range of pressure gradients and volumetric rates, with emphasis on trabecular structures. This might shed light on pathophysiological processes leading to damage associated with insufficient CSF flow in patients with optic nerve compartment syndrome.

Features of the construction of canals in half-cut-half-fill

This study examines the construction features of the Bustan Canal in the Republic of Karakalpakstan, designed with a half-cut-half-fill method to optimize water supply and drainage capabilities. Given the region’s high groundwater levels, canals were constructed in trenches, serving dual purposes of irrigation and open drainage to mitigate flooding risks. The primary goal was to enhance the canal’s efficiency coefficient to 0.85 by applying concrete lining to its slopes and bed, transitioning from mechanical to gravity irrigation sourced from the Tuyamuyun Reservoir on the Amu Darya River. The study highlights the advantages of using excavated soil for embankment construction, which significantly reduces transportation costs. Physical properties and granulometric composition of the soils were analyzed in accredited laboratories, confirming optimal compaction densities between 1.72 g/cm³ and 1.77 g/cm³ at moisture contents ranging from 17% to 20%. The findings underscore the importance of this canal system in supporting agriculture over an area of 100,000 hectares, enhancing water management practices in Southern Karakalpakstan.

Drainage Performance of Long Longitudinal Slope and High Safety Permeable Asphalt Pavement

Permeable asphalt pavement refers to an asphalt mixture layer with an air void content of more than 18% and internal water permeability and drainage capabilities that can quickly drain away water on the road surface, improve rainy day travel safety, and improve ride comfort. This paper aims to explore the optimal asphalt mixture design for long longitudinal slope pavement (referred to as the FAM mixture). By using CT scanning technology to analyze the air void content of different rotated and compacted asphalt mixture specimens and extensively testing and evaluating the performance of permeable pavement mixtures, the following conclusions are drawn: Based on the research philosophy of functional integration, a new asphalt mixture gradation suitable for long longitudinal slope roads is proposed, with the optimal key factor composition being: 0.075 mm passing rate of 7%, 2.36 mm passing rate of 20%, 9.5 mm passing rate of 55%, and an oil-stone ratio of 4.8%. The FAM mixture was divided into three parts for air void analysis, with the upper part having a slightly higher air void content than the lower part. The air void distribution diagram of the FAM mixture is concave, with higher air void rate curves on both sides and a lower middle curve. Through dynamic modulus testing, the strength requirement for the road asphalt mixture in the pavement structure design was evaluated. It was found that at high temperature conditions (50 °C), the minimum dynamic modulus value of the FAM mixture was 323 MPa, with a peak value of 22,746 MPa at a temperature of −10 °C and a frequency of 25 HZ. The dynamic modulus value at high temperature conditions is lower than at low temperature conditions, while the dynamic modulus value at high frequency conditions is higher than at low frequency conditions. This study provides useful information and experimental data for the design of new asphalt mixtures for long longitudinal slope roads and has conducted in-depth research on the air void distribution and performance of the mixture, providing strong support for related research fields and practical applications.

An ensemble framework for farmland quality evaluation based on machine learning and physical models

Farmland quality (FQ) evaluation is crucial to curb agricultural land's “non-grain” behavior and promote ecological nitrogen trade-off in North China. However, a promising approach to obtain the verified spatial distribution of nitrogen emissions remains to be developed, making it difficult to achieve the precise FQ estimation. Facing this issue, we present a Machine Learning (ML) - Nitrogen Export Verification (NEV) ensemble framework for the precise evaluation of FQ, taking the Beijing-Tianjin-Hebei 200 km traffic zone (zone) as the case. This was done by employing physical models for the precisely spatial estimation of Nitrogen Export (NE) values and then using ML methods to compute the spatial distribution of FQ using the Farmland Quality Evaluation System (FQES) indicators. We found: (1) the ML - NEV framework showed promising results, as the relative error of the NEV method was lower than 5.25 %, and the Determination coefficient of the ML method in FQ evaluation was higher than 0.84; (2) the FQ results within the zone were mainly good-quality areas (~47.25 % and primarily concentrated in the southwest-northeast regions) with improvement significance, with Fractal Dimension, NE values, and unbalanced Irrigation or Drainage Capabilities serving as the primary driving factors. Our results would be helpful in offering decision support for improving FQ based on refined grids, benefiting to Agribusiness Revitalization Plans (i.e., safeguarding grain yield, activating agribusiness development, Etc.) in developing countries.

Enhanced fluid drainage using a novel multi-pod drainage catheter: An in vitro evaluation.

A multi-pod catheter (MPC) is a large drainage catheter that can house multiple smaller retractable (MPC-R) and deployable catheters (MPC-D) within the body. The drainage capabilities and resistance to clogging of a novel MPC have been assessed. The drainage capabilities are evaluated by placing the MPC in a bag of either a non-clogging (H2O) or clogging medium. The results are then compared to matched-size single-lumen catheters with either a close (CTC) or open tip (OTC). The means of five test runs were used to measure drainage rate, maximum drained volume (MaxDV), and time to drain the first 200mL (TTD200). In the non-clogging medium, MPC-D had a slightly higher MaxDV than MPC-R, and higher flow rate than CTC and MPC-R. Moreover, MPC-D needed less TTD200 than MPC-R. In the clogging medium, MPC-D had a higher MaxDV than CTC and OTC, higher flow rate, and faster TTD200 than CTC. However, comparison with MPC-R showed no significant difference. The novel catheter may offer superior drainage compared to the single-lumen catheter in a clogging medium, implying various clinical applications, particularly when clogging is a potential risk. Further testing may be required to simulate various clinical scenarios.

Plastic Deformation Characteristics and Calculation Models of Unbound Granular Materials under Repeated Load and Water Infiltration

Unbound granular materials (UGMs) have advantages in their water storage and drainage capabilities in permeable pavement, which is a benefit for urban sustainable development. The plastic strain of UGM is a crucial mechanical property that affects its design and construction. During its service life, repeated load only, repeated load after infiltration, and simultaneous action with load and infiltration are the three inevitable working conditions that will impact plastic strain, especially dynamic water infiltration. How these working conditions influence plastic strain needs to be focused on and solved. This study conducted laboratory tests to investigate plastic strain considering factors such as loading strength and repetitions, as well as infiltration number and duration. The results showed that the plastic strain and plastic strain rate exhibited similar variations during the repeated load only test and repeated load after infiltration test. The plastic strain changed significantly with different infiltration numbers but had relatively small variations in terms of the plastic strain rate. Longer infiltration duration led to greater plastic strain. With the simultaneous action, the plastic strain presented different variation to the other two conditions. The first and second infiltrations had a more obvious influence on the plastic strain when infiltration was applied. Calculation models were established to predict the effects of loading strength and repetitions as well as infiltration number and duration on plastic strains. For the repeated load only test, an error of 4.6% was observed. In terms of the infiltration number and duration, the errors were found to be 18.5% and 8.5%, respectively. The power function and Sigmoidal Logistic model were used to establish calculation models under the simultaneous action test with a maximum error of 11.5% ranging from 100 to 60,000 repetitions. The proposed calculation models can characterize plastic strain under the three working conditions very well, which can help in the design and construction of fully permeable pavement.

Comparative life cycle assessment and life cycle cost analysis of centralized and decentralized urban drainage systems: A case study in Zhujiang New Town, Guangzhou, China

Rapid urbanization and global climate change are increasing the vulnerability of cities to urban flooding, thereby posing significant challenges to the design and implementation of urban drainage systems (UDS). Traditional centralized UDS have been found ineffective in mitigating the uncertainty of future flood risks. Consequently, the need to explore resilient alternatives, such as decentralized UDS, has gained importance. Of particular interest is the coupled approach of grey infrastructure (GREI) and low-impact development (LID), which merges the drainage capabilities of GREI with the versatility and sustainability of distributed green infrastructure. However, there are limited studies assessing the environmental and economic impacts of both centralized and decentralized LID-GREI UDS using integrated Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) methods. This study, using Zhujiang New Town, Guangzhou, China, as a case study, found that decentralized UDS outperformed centralized UDS from both environmental and economic perspectives, mainly due to smaller pipeline scale and lower maintenance frequency. Furthermore, though the LID-GREI UDS showcased more substantial environmental impacts and higher economic costs compared to GREI UDS, the hydrological benefits obtained from LID operation can counteract part of these environmental impacts. In a unique perspective, this study considers the payback periods for centralized and decentralized LID-GREI UDS, estimating them to be 70 and 55 years respectively, when taking economic implications and hydrologic benefits into an overall consideration. Overall, the findings underscore that the LID-GREI UDS, particularly the decentralized LID-GREI, presents a more sustainable and cost-effective strategy for mitigating pluvial flooding compared to GREI UDS. This study provides comprehensive insights into effective and cost-efficient strategies for alleviating urban flooding vulnerabilities through UDS design and implementation.

Investigating the Properties of Drainage Concrete Pavement through the Pore Creation Method: A Study

Background: Over the past decade, the pervious concrete pavement has become a popular innovation due to its highly porous spaces that allow for easy air and water flow from the surface to the underlying layers. However, the increased void content could potentially make the concrete weaker and less durable, which creates a need for alternative methods to maintain its strength while improving its drainage capabilities. Objective: This study aims to analyze the characteristics of drainage concrete pavement using a novel method for creating pore structures. Methods: To address the challenges of conventional concrete pavement, various pore patterns and diameters were examined, including a 2x2, 3x3, and 4x4 row arrangement with pore diameters of 2, 3, and 4 mm. The concrete mixture was formulated to comply with the standards established by the Department of Highways in Thailand. The study analyzed both the fresh concrete properties, such as slump test and setting time, and the hardened properties, such as compressive strength, flexural strength, and water absorption. The draining capability was evaluated through water permeability performance and the clogging effect was measured by very fine sand particles. Results: The test results showed that the slump value of concrete complied with the design specifications, and the initial setting time was recorded to be 230 minutes. The compressive strength and flexural strength tended to decrease while water absorption tended to increase as the pore pattern arrangement and pore diameter increased. However, the compressive strength of all mixtures exceeded 85% when compared to the control. Additionally, the water permeability coefficient ranged between 2.69-18.52 mm/s, and the permeability coefficient tended to decrease when the clogging effect occurred in the range of 18.18-37.27%. Conclusion: The findings of this study contributed to our understanding of the properties and behavior of concrete with pore creation. By refining our knowledge of the intricate correlation between porosity and compressive strength, it has become evident that reducing porosity is necessary to enhance the mechanical properties of concrete and ensure its long-term durability. Furthermore, sustainable infrastructure applications can improve the relationship between permeability and effective porosity through construction techniques.

Evaluation of Water Network Construction Effect Based on Game-Weighting Matter-Element Cloud Model

Water network construction is one of the important ways to solve complex water problems at present. It is crucial for the optimal allocation of water resources, flood control, disaster reduction, protection of water ecology, water security, and sustainable urban development. Accordingly, this study formulates an index system for assessing the efficacy of water network construction based on the Driving Force–Pressure–State–Influence–Response (DPSIR) model, taking into account the four dimensions of optimal allocation of water resources, flood control and disaster reduction in river basins, protection of water ecosystems, and intelligent water network management. The proposed index system comprises four key aspects, which are utilized to evaluate the effectiveness of water network construction efforts. Then, the game-weighting method and the matter-element extension method improved by the cloud theory established an evaluation model to evaluate and compare the water network construction effects of the two cities in Henan Province. Finally, the GM (1,1) model was used to evaluate the water network construction effects, and future trends were predicted. The results show the following: (1) On the whole, the effect of water network construction in the two cities is constantly improving; (2) There has been a significant improvement in the intelligent management of water networks. The main reason for this result is that the “Internet +” has promoted the intelligent construction of water networks; (3) The water ecological environment, flood control, and drainage capabilities continued to improve, which has largely guaranteed the basic security bottom line of urban development space; (4) The advancement and utilization of water resources has undergone gradual improvements over time, with key impact metrics centered on water supply safety factors and the development and utilization of water resources. As water supply sources continue to diversify, it is expected that the aforementioned situation will be ameliorated in the future; (5) The predicted value shows that the water network construction of the two cities can basically meet the planned value of each index when the water network construction reaches the planning level. This paper provides help to promote the sustainable use of water resources and ensure the sustainable development of cities.

Investigating the Seepage Characteristics of an Open-Graded Friction Course Using Finite Element Modeling

An open-graded friction course (OGFC) is an asphalt mixture designed with a large air void (AV) content that provides enhanced drainage capability at the surface. The main objectives of this study were to investigate the impacts of selected factors (i.e., the OGFC thickness and coefficient of permeability, the permeability of the underlying layer, and traffic loading) on the drainage characteristics of the OGFC, develop a quantitative tool to simulate the deterioration in the functional performance of the OGFC, and propose new guidelines for the AV content of OGFC for optimum functionality. To this end, a three-dimensional finite element (FE) model was developed to evaluate the impacts of OGFC permeability, OGFC layer thickness, underlying layer permeability, rain intensity, and traffic volume on the seepage characteristics of OGFC pavements. The impacts of these factors were evaluated by calculating the time at which the OGFC surface reaches overflow condition ( TC). Statistical analysis of the results showed that all considered factors had a significant impact on OGFC seepage characteristics, except OGFC permeability. In addition, an artificial neural network (ANN) model was developed to predict TC without the need for FE modeling. Results indicated that the ANN model predicted TC accurately with R2 values of 0.99 and 0.98 in the training and validation stages, respectively. The results also indicated that the model accurately predicted TC over time for OGFC pavements with a root-mean-square error of less than 5.0%. Simulation runs were conducted using the developed FE model under different OGFC AV content conditions and rain intensities. Results revealed that an OGFC layer with an AV content of 16% would provide adequate drainage performance while minimizing OGFC durability issues.

Approximation method for the sewer drainage effect for urban flood modeling in areas without drainage-pipe data

Introduction: The underground drainage-pipe network is one of the vital components of a modern city, and it plays an important role in preventing or mitigating urban flooding. Thus, pipe network data are necessary for simulation of the entire urban rainfall–runoff process. However, pipe network data are sparse or unavailable in most urban areas.Methods: To solve this problem, we developed a novel approximation method that can be used calculate the drainage capacity of the pipe system. This method is named the road-drainage method, and it works under the assumption that the pipe network functions by subtracting the corresponding mass from the water conservation equation only from areas of road. The mass is determined from weir flow formulas together with the road properties and correction for this mass is applied to the rainfall source term.Results: Two test cases were used to compare the performance of the new method with an existing method, under which mass is subtracted from the entire area during the rainfall–runoff process. The results showed that the new method considerably improves the accuracy of simulated peak volume, with an improvement of 2.62%–58.75% compared with the existing method across various scenarios. Moreover, the proposed new method reduces the time shift of the rise and peak of surface inundation by 10–45 min in various scenarios, which reflects a more realistic model of the rainfall–runoff process.Discussion: These results demonstrate that the proposed new method can represent the drainage capability more accurately and is more consistent with reality. The road-drainage method has promising potential for application in urban flood simulation in areas without drainage system data and for the support of large-scale urban hydrologic modeling.

A novel cathode flow field for PEMFC and its performance analysis

A good flow field design is important to the proton exchange membrane fuel cell (PEMFC) performance, especially under a high current density region, which is dominated by concentration polarization. Motivated by the variable cross-section channel idea, in this study, a novel flow field containing a converging-diverging (C-D) pattern is proposed. A three-dimensional multiphase model is established to study its performance. The numerical results show that it outperforms the conventional straight channel and only depth-variant channel. In the novel flow field the enhanced under land cross flow and higher effective mass transfer coefficient both improve the reactant transport. The effects of operating conditions, like stoichiometric ratio and operating pressure, on cell output performance are studied. It is found that a higher promotion rate can be obtained by increasing the stoichiometric ratio, but increasing the operating pressure has little effect. The droplet dynamic behavior in the C-D channel and straight channel are studied, and the results prove the better drainage capability of the novel flow field.

Engineered Sandwich‐Structured Composite Wound Dressings with Unidirectional Drainage and Anti‐Adhesion Supporting Accelerated Wound Healing (Adv. Healthcare Mater. 8/2023)

Composite Wound Dressings In article 2202685 by Peng Yan, Xinguo Hou, and co-workers, a novel sandwich-structured composite wound dressing (SCWD), integrating a superlyophobic polydimethylsiloxane layer, a superlyophilic gauze layer, and a lyophobic PDMS layer, with particular unidirectional drainage capability and anti-adhesion properties, is presented. The application of SCWDs can reduce wound infection, avoid tissue avulsion when replacing dressings, and accelerate wound healing by approximately 20%. Aided by lyophilized powders of stem cells supernatant, the wound healing process is further improved.

High-Performance Proton Exchange Membrane Fuel Cells Enabled by Highly Hydrophobic Hierarchical Microporous Carbon Layers Grafted with Silane

The employing of a microporous layer (MPL) with an appropriate pore size distribution and hydrophobicity between the carbon paper substrate and catalyst layer of proton exchange membrane fuel cells (PEMFCs) plays a decisive role in the management of gas transport and the crucial prevention of water flooding. However, enhancing the performance of PEMFCs by directly altering the structure of MPL has rarely been reported. The present work addresses this issue by fabricating hierarchical porous carbon (HPC) enabled MPLs via a dual template method employing zinc oxide and sodium chloride, and a silane-coupling agent is chemically grafted to HPC components of the MPL to improve water drainage instead of applying a conventional hydrophobic treatment. The physical and electrochemical properties of gas diffusion layers formed with different MPLs are analyzed, and the results indicate that the proposed MPL with excellent water drainage and efficient gas transport capability facilitates a higher output power density (863.62 mW cm–2) and lower mass transport impedance superior to a conventional MPL. This work provides a generic and feasible structure design for the development of MPLs that significantly improves the performance of PEMFCs.