Search Results (77)

Hydraulic erosion from suspended sediment is a major degradation mechanism in Francis turbines of sediment-laden rivers, especially in Andean hydropower plants. This study presents a Python3.9-based computational tool integrating the empirical Oka erosion model within a Lagrangian particle tracking framework, coupled to single-phase CFD in OpenFOAM 10. The novelty lies in a reduced-domain approach that omits the spiral casing and replicates its particle-induced swirl via a custom algorithm, lowering meshing complexity and computational cost while preserving erosion prediction accuracy. The method was applied to a full-scale Francis turbine at the San Francisco hydropower plant in Ecuador (nominal discharge 62.4 m³/s, rated output 115 MW, rotational speed 34.27 rad/s), operating under volcanic and erosive sediment loads. Maximum erosion rates reached ~1.2 × 10⁻⁴ mm³/kg, concentrated on runner blade trailing edges and guide vane pressure sides. Impact kinematics showed most collisions at near-normal angles (85°–98°, peak at 92°) and 6–9 m/s velocities, with rare 40 m/s impacts causing over 50× more loss than average. The workflow identifies critical wear zones, supports redesign and coating strategies, and offers a transferable, open-source framework for erosion assessment in turbines under diverse sediment-laden conditions. Full article

In recent years, pelvic organ prolapse (POP) cases have been rising, affecting women’s quality of life. Synthetic surgical transvaginal meshes used for POP treatment were withdrawn from the United States market in 2019 due to high risks, including infection, vaginal mesh erosion, and POP reoccurrence. Biodegradable mesh implants with three-dimensional printing technology have emerged as an innovative alternative. In this study, polycaprolactone (PCL) meshes for POP repair were fabricated using melt electrospinning writing (MEW) and mechanically evaluated through uniaxial tensile tests. Following this, they were coated with antibiotics—azithromycin, gentamicin sulfate, and ciprofloxacin—commonly used for genitourinary tract infections. Zone inhibition and biofilm assays evaluated antibiotic effectiveness in preventing mesh infections by Escherichia coli, and methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus. The meshes presented a mechanical behavior closer to vaginal tissue than commercially available meshes. Fourier transform infrared analysis confirmed antibiotic incorporation. Ciprofloxacin demonstrated antibacterial activity against MRSA, with a 92% reduction in metabolic activity and a 99% biomass reduction. Gentamicin and ciprofloxacin displayed inhibitory activity against MSSA and E. coli. Scanning electron microscopy images support these conclusions. This methodology may offer a more effective, patient-friendly solution for POP repair, improving healing and the quality of life for affected women. Full article

In view of the problems of slow heat storage process and uneven temperature distribution in the existing phase change heat accumulator, a new type of mesh fin heat accumulator was designed and developed which increased the contact area between the phase change material (PCM) and the fins, enhanced the apparent thermal conductivity of the PCM, improved the heat storage efficiency of the heat accumulator, blocked the PCM, improved the natural convection erosion of the PCM on the upper and lower parts of the heat accumulator, and melted the PCM in each area more evenly. Fluent15.0 was used to numerically simulate the heat storage process of the mesh fins heat accumulator with the finite volume method. The composite PCM prepared by adding 10% mass fraction of expanded graphite to paraffin wax was used as the heat storage material. A 2D, non-steady-state model, incompressible fluid, and the pressure-based solution method were selected. The energy model and the solidification and melting model based on the enthalpy method were used to simulate and calculate the phase change process of PCM. The PISO algorithm was used. The influences of the structural parameters of the mesh fins on the heat storage condition of the heat accumulator were investigated by numerical simulation. The results showed that with the increase in the radius R of the mesh fin, the heat storage time decreased first and then increased. With the increases in vertical fin thickness c, mesh fins thickness δ, and vertical fins number N, the heat storage time decreased. The optimal mesh fin structure parameters were R = 33.5 mm, c = 3 mm, δ = 3 mm, and N = 8, and the heat storage time was 8086 s, which is 47.8% shorter than that of the concentric tube heat accumulator. Otherwise, with the increases in vertical fin thickness c, mesh fins thickness δ, and vertical fins number N, the PCM volume decreased, which shortened PCM melting time. Full article

The precision casting of nickel-based single-crystal superalloys imposes stringent requirements on the high-temperature stability and chemical inertness of ceramic shell face coats. To address the issue of traditional EC95 shells (95% Al₂O₃–5% SiO₂) being prone to react with the alloy melt at elevated temperatures, thereby inducing casting defects, this study proposes a lanthanide oxide-based ceramic face coat material. Three distinct powders—LaAlO₃ (LA), LaAlO₃/La₂Si₂O₇ (LAS), and LaAl₁₁O₁₈/La₂Si₂O₇/Al₂O₃ (LA11S)—are successfully prepared through solid-phase sintering of the La₂O₃-Al₂O₃-SiO₂ ternary system. Their slurry properties, shell sintering processes, and high-temperature performance are systematically investigated. The results demonstrate that optimal slurry coating effectiveness is achieved when LA powder is processed with a liquid-to-powder ratio of 3:1 and a particle size of 300 mesh. While LA shells show no cracking at 1300 °C, their face coats fail above 1400 °C due to the formation of a La₂Si₂O₇ phase. In contrast, LAS and LA11S shells suppress cracking through the La₂Si₂O₇ and LaAl₁₁O₁₈ phases, respectively, exhibiting exceptionally high-temperature stability at 1400 °C and 1500 °C. All three shells meet the high-temperature strength requirements for CMSX-4 single-crystal alloy casting. Interfacial reaction analysis and Gibbs free energy calculations reveal that Al₂O₃-forming reactions occur between the novel shells and alloy melt, accompanied by minor dissolution erosion without other chemical side reactions. This work provides a high-performance face coat material solution for investment casting of nickel-based superalloys. Full article

A typical county for traditional village conservation in China is Songyang County. It is renowned for its ancient rammed earth dwellings, which exhibit a unique microclimate and possess significant historical value. However, high precipitation and acid rain under the subtropical monsoon climate have caused severe surface erosion, including cracking and spalling. This study focuses on traditional rammed earth dwellings in Chenjiapeng Village, Songyang County, combining field surveys, experimental analysis, and microscopic characterization to systematically investigate erosion mechanisms and protection strategies. Techniques, such as drone aerial photography, X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and microbial diversity detection, were employed to elucidate the anti-erosion mechanisms of gray–green biological crusts on rammed earth surfaces. The results indicate that algal crusts enhance surface compressive strength and shear resistance through macroscopic coverage (reducing raindrop kinetic energy and moisture retention) and microscopic extracellular polysaccharide-cemented soil particles forming a three-dimensional network. However, acidic environments induce metabolic acid release from algae, dissolving cementing materials and creating a “surface protection-internal damage” paradox. To address this, a “transparent film-biofiber-acid inhibition layer” composite biofilm design is proposed, integrating a biodegradable polylactic acid (PLA) mesh, algal attachment substrates, and calcium carbonate microparticles to dynamically neutralize acidic substances, achieving synergistic ecological protection and cultural heritage authenticity. This study provides innovative solutions for the anti-erosion protection of traditional rammed earth structures, emphasizing environmental compatibility and sustainability. Full article

Tip vortex cavitation not only impacts the hydrodynamic performance of a propeller but also results in vibrations, noise, and erosion. In this study, the effect of blade number on propeller tip vortex cavitation is investigated using computational fluid dynamics (CFD) methods. Numerical simulation is performed regarding four model propellers with blade numbers varying from one to four. These propellers have the same blade geometry as the E779A propeller. Large eddy simulation (LES) and the Schnerr–Sauer cavitation model are used to solve tip vortex cavitation with local mesh refinement according to the spiral tip vortex trajectory. The hydrodynamic performance and tip cavitation of the propellers are solved and analyzed to reveal the fluid mechanism of tip vortex formation. The effect of blade number on wake velocity and wake vorticity is discussed. Numerical analysis showed that the increase in blade number leads to a reduction in the thrust and torque of a single blade, although the total thrust and torque of all blades increased. The present study takes new insights to the suppression of tip vortex cavitation, which benefits propeller design. Full article

Background: Pelvic organ prolapse (POP) significantly impacts women’s quality of life, especially in postmenopausal patients. Although laparoscopic sacrocolpopexy (LSC) is the gold standard for advanced apical prolapse, its complexity and risk of complications have led to alternative approaches like laparoscopic lateral suspension (LLS), a minimally invasive technique with promising results. Methods: A comprehensive search using PubMed databases was performed. The search was conducted from June 2024 to September 2024. The search string used was as follows: (pelvic organ prolapse) AND (lateral suspension) OR (laparoscopic lateral suspension). We included randomized controlled trials, prospective cohort studies, prospective observational studies, and case studies. We excluded retrospective studies, small case series, case reports, and articles not published in English. All selected articles were screened based on the titles and abstracts. Relevant data were extracted and tabulated. Results: An overall number of 12 studies were included in our analysis. LLS demonstrated high anatomical success rates: 91.15% for the anterior, 94.95% for the central, and 86.55% for the posterior compartments. The randomized controlled studies exhibit comparable effectiveness between both methods (LLS vs. LSC) and LLS appears to be the best option for anterior repair or anterior–apical repair. Patient satisfaction rates exceeded 90%, with reduced operative times (123 ± 33 min and 193 ± 55.6 min for ALS and ASC, respectively). According to the Claiven–Dindo scale, 0.17% of postoperative complications were graded more than III. The rate of mesh erosion was 0% to 10%. The technique showed particular benefit for uterine preservation and in obese patients but was less effective for severe posterior prolapse. Conclusions: Laparoscopic lateral suspension offers a safe, effective alternative for POP management, with significant anatomical and functional benefits. Its minimally invasive nature, shorter surgery time, and high satisfaction rates make it suitable for tailored patient care. Further studies should standardize evaluation metrics and assess long-term outcomes. The review was not registered. No funding was received. The authors declare no competing interests. Full article

Pelvic organ prolapse (POP) is a common condition among women, characterized by the descent of pelvic organs through the vaginal canal. Although traditional synthetic meshes are widely utilized, they are associated with complications such as erosion, infection, and tissue rejection. This study explores the design and fabrication of biodegradable auxetic implants using polycaprolactone and melt electrowriting technology, with the goal of developing implants that closely replicate the mechanical behavior of vaginal tissue while minimizing implant-related complications. Four distinct auxetic mesh geometries—re-entrant Evans, Lozenge grid, square grid, and three-star honeycomb—were fabricated with a 160 $\mathrm{\mu }$m diameter and mechanically evaluated through uniaxial tensile testing. The results indicate that the square grid and three-star honeycomb geometries exhibit hyperelastic-like behavior, closely mimicking the stress–strain response of vaginal tissue. The re-entrant Evans geometry has been observed to exhibit excessive stiffness for applications related to POP, primarily due to material overlap. This geometry demonstrates stiffness that is approximately five times greater than that of the square grid or the three-star honeycomb configurations, which contributes to an increase in local rigidity. The unique auxetic properties of these structures prevent the bundling effect observed in synthetic meshes, promoting improved load distribution and minimizing the risk of tissue compression. Additionally, increasing the extrusion diameter has been identified as a promising strategy for further refining the biomechanical properties of these meshes. These findings lay a solid foundation for the development of next-generation biodegradable implants. Full article

This article examines the combined use of UAV (Unmanned Aerial Vehicle) photogrammetry and TLS (Terrestrial Laser Scanning) to detect changes in coastal cliffs in the Strunjan Nature Reserve. Coastal cliffs present unique surveying challenges, including limited access, unstable reference points due to erosion, GNSS (Global Navigation Satellite System) signal obstruction, dense vegetation, private property restrictions and weak mobile data. To overcome these limitations, UAV and TLS techniques are used with the help of GNSS and TPS (Total Positioning Station) surveying to establish a network of GCPs (Ground Control Points) for georeferencing. The methodology includes several epochs of data collection between 2019 and 2024, using a DJI Phantom 4 RTK for UAV surveys and a Riegl VZ-400 scanner for TLS. The data processing includes point cloud filtering, mesh comparison and a DoD (DEM of difference) analysis to quantify cliff surface changes. This study addresses the effects of vegetation by focusing on vegetation-free regions of interest distributed across the cliff face. The results aim to demonstrate the effectiveness and limitations of both methods for detecting and monitoring cliff erosion and provide valuable insights for coastal management and risk assessment. Full article

This paper presents the results of a testbench regarding the effects of liquid water content in the turbine stage of a fuel-cell charging system. The testbench simulates the exhaust conditions of a PEM fuel cell to evaluate erosion potential in a single-stage aluminum turbine and assess the effectiveness of liquid water separators. Key factors such as changes in turbine geometry and performance were analyzed. Erosion influence to low-cycle fatigue potential is assessed via eigenfrequency measurements. Turbine stage-efficiency measurements are used to calculate the thermodynamic impact of erosion. Three-dimensional scanning, eigenfrequency measurements, and performance map calculations showed a 5.4% crater-to-blade thickness change, <0.6% frequency shift, and finally, a <0.1% change in efficiency, indicating that erosion remained at the incubation stage. Centrifugal separators showed superior performance compared to mesh types. The hardest aspect of the work was to minimize measurement error. Full article

Introduction: Pelvic organ prolapse is a common condition that can affect 50% of parous women. The surgical management can be divided into two approaches: A trans-vaginal and a trans-abdominal approach. In view of current controversies and discrepancies between guidelines, this review aims to scope the historically available data on synthetic meshes in the management of POP mainly on outcomes and complications of the trans-vaginal approach and the trans-abdominal approach. Methods: This study is a narrative review of the use of synthetic meshes in POP surgery. The different indications, the results, and comparisons to other surgical management were collected using MEDLINE and Google Scholar. Results: Regarding the trans-vaginal approach, 31 articles were included. The anatomical success rate is high, around 90%. However, this technique was recently considered cost-ineffective mostly because of high rates of erosions, ranging from 4 to 40% depending on the series. Obesity seems to be the most important risk factor of mesh erosion, followed by age and smoking. Regarding the trans-abdominal approach, 36 articles were included. In the literature, anatomical success is between 70 and 95%, with an erosion rate between 0 and 11%. Minimally invasive sacrocolpopexy and open sacrocolpopexy seem to be equally effective on anatomical outcomes and recurrence rates. Concomitant total hysterectomy might be effective but may be associated with more mesh erosions. Concomitant laparoscopic supracervical hysterectomy may be the preferred option for patients with cervical and uterine lesions but should not be performed for the sole purpose of reducing the occurrence of endometrial carcinoma, especially when uterine preservation seems effective and is associated with less blood loss and shorter operating time. Conclusion: Our review reports limited application for trans-vaginal repair because of high complications rates, leading countries to suspend their utilization. Our review reports a gold standard application for trans-abdominal sacrocolpopexy. The use of synthetic meshes in trans-abdominal sacrocolpopexy for POP repair provide durable cure rates with a lower rate of mesh-related complications and therefore may be considered the gold standard approach. Full article

This article proposes an arbitrary polygonal hybrid stress element considering gravity. It derives an arbitrary polygonal hybrid stress element considering gravity alone for slope stability related engineering analysis. In the stability analysis of slopes, slope disasters caused by gravity erosion have recently become an urgent problem to be solved through engineering. The traditional finite element analysis of slope stability faces problems such as a large number of divided elements and slow calculation efficiency. By introducing high-order stress fields through stress hybridization elements, accurate results can be simulated using a small number of elements. When dividing the mesh, most of the cell shapes are asymmetric, and the shape of the cell can be any polygon, which can simulate the geometric shape of complex slopes well and more accurately calculate the stress distribution in different parts, thus accurately simulating the stability situation in engineering. By comparing with the corresponding commercial software MARC 2020, the effectiveness and efficiency of the element were verified. It has been proven that any polygonal hybrid stress element has the advantage of flexible mesh division, which can obtain high-order stress fields and stress concentration phenomena with fewer elements. Applying this element to practical problems of slopes in engineering has also achieved good calculation results. Full article

Fluid–soil interaction plays a pivotal role in various geotechnical engineering applications, as it significantly influences processes such as erosion, sediment transport, and soil stability. Modeling fluid–soil particle interactions in these contexts presents substantial challenges due to the inherent complexity of the interactions occurring across multiple characteristic scales. The primary challenge lies in the vast disparities in magnitude between these scales, which demand sophisticated modeling techniques to accurately capture the intricate dynamics involved. Coupled fluid–soil particle models have emerged as essential tools for understanding the mechanisms underlying fluid–soil interactions. Among these, the CFD-DEM (computational fluid dynamics–discrete element method) approach has gained significant attention. This method provides an effective compromise between high-resolution sub-particle fluid modeling and coarser mesh-based techniques for fluids and particles. By doing so, CFD-DEM facilitates large-scale simulations while maintaining computational efficiency, making it a promising solution for studying fluid–soil interactions in complex geotechnical scenarios. This review highlights the application of CFD-DEM models in geotechnical engineering, with a specific focus on soil erosion processes and the critical role of turbulent flow. It explores various fluid–soil particle interaction computational mechanisms and their implications for erosion dynamics, emphasizing several key aspects, including the following: laminar vs. turbulent flow models: understanding the distinctions between flow regimes is critical for accurately predicting fluid-induced soil particle movement. Shear stress effects: the influence of flow-induced shear stress on the detachment of soil particles is analyzed, particularly in erosion-prone environments. Sediment transport mechanisms: factors such as particle size, density, and water velocity are examined for their roles in governing sediment transport. Knowledge gaps and future directions: these involve identifying unresolved issues in current fluid–soil interaction models, with an emphasis on improving the accuracy and scalability of CFD-DEM simulations. By delving into these aspects, the review aims to advance the understanding of fluid–soil interactions and provide insights into optimizing modeling techniques for geotechnical engineering applications. It also outlines future research directions to bridge existing knowledge gaps, emphasizing the importance of integrating advanced turbulence modeling and computational strategies to enhance the predictive capabilities of fluid–soil interaction frameworks. Full article

Armor blocks are extensively deployed to shield vital coastal facilities against wave erosion. Evaluating the wave run-up and reflection under wave impact is essential for the engineering design of new ecological quadrangular hollow blocks. This study constructs a three-dimensional numerical model employing the open-source CFD software OpenFOAM-v2206 to analyze these processes for the new blocks. The model’s accuracy was confirmed by comparing its predictions with physical modelling tests. Model results accurately captured the variation in hydrodynamic parameters, as well as the energy dissipation properties of the new blocks. Sensitivity analysis indicated that both the wave reflection coefficients and run-up are considerably affected by mesh sizes, while velocity distributions and pressure fields were less affected by mesh. Finally, the model was utilized to examine how wave run-up and reflection for the new ecological quadrilateral hollow block are influenced by factors such as wave period, water depth, wave height, wave breaking characteristics, and wave steepness. The findings in this study provide valuable insights into novel design and safety assessment of new ecological quadrangular hollow blocks. Full article

To address the issues of pipeline corrosion and erosion during ground testing, this paper presents an innovative electromagnetic ultrasonic thickness measurement system that utilizes ZigBee wireless communication technology. The system employs a ZigBee mesh topology for creating a wireless distributed network, where node devices carry out multi-point monitoring in a configuration of “one master, multiple”. Each node is powered by an STM32 embedded control chip and fitted with ultrasonic sensors. Slave nodes transmit the real-time data they collect to a server via the master node, thus enabling remote monitoring of the system through a web interface. The system incorporates an enhanced data filtering algorithm, allowing for precise monitoring of the pipeline wall thickness and providing immediate data feedback. An experimental validation of the system’s stability and long-distance transmission capabilities was performed on a simulated platform, confirming its viability and applicability for real-world engineering applications. Full article