Wall Function Research Articles

An explicit multilevel power turbulent wall function based on the de-thresholding Douglas–Peucker algorithm

Wall functions are extensively applied in engineering simulations with turbulence. They facilitate a significant increase in the scale of the grids next to the wall, which in turn reduces the total number of grids needed. This optimization enhances computational efficiency, making the simulation process more effective and streamlined. However, the current commonly used wall functions, such as the Spalding wall function, are an implicit expression that needs to be solved iteratively, which affects the computational efficiency, and the multilayer segmented wall function is not smoothly articulated, which affects the fidelity. In this study, based on flat plate direct numerical simulation (DNS) data, combined with structural ensemble dynamics theory, the de-thresholding Douglas–Peucker algorithm is introduced to construct an explicit wall function expression in the form of multilevel power exponential concatenated multiplication. The comparison of the new wall function against DNS data reveals that it demonstrates superior fitting accuracy in contrast to the traditional ones, and eliminates the need for manual calibration, reduces subjective influence, and enhances reliability. The numerical simulation outcomes for the flat plate boundary layer and a series of airfoils showcase the new wall function's exceptional accuracy, which not only meets but also surpasses the demanding standards of engineering practice.

A parametric investigation of Dual-throat nozzle bypass channel configurations for advanced Aviation applications

The Bypass Dual-Throat Nozzle (BDTN) has garnered growing attention due to its remarkable thrust vectoring capabilities. This type of nozzle boasts broad application prospects as it achieves deflection control of the jet stream merely through regulating the opening and closing of bypass channels. Our comprehensive study delves deeply into the intricate parameterization of the bypass channel within the BDTN. Research has demonstrated that utilizing Fluent software in conjunction with the Realizable k-epsilon turbulence model, standard wall functions, and the Sutherland formula for viscosity coefficient approximation can yield a relatively accurate representation of the vector flow field structure within the BDTN. Following the validation of the numerical computation methodology employed in this study, we have investigated the influence of factors such as bypass channel radius, precise valve positioning, and actuation direction on the nozzle's vectoring performance. Key findings indicate that, due to the relatively small proportion of secondary flow, the radius of the bypass channel has minimal impact on the thrust vector angle. The positioning of the valve and its opening direction are critical in determining the thrust vector angle, requiring careful consideration during the design and optimization process. Fully opening the bypass channel does not necessarily yield the maximum thrust vector angle. Moreover, the total pressure, velocity, position, and direction of the secondary flow within the bypass channel exert a more profound influence on the nozzle's vector performance compared to the mere presence of the secondary flow itself. Notably, the forward opening method of the valve emerges as the preferred choice, as it facilitates more precise later vector control.

Improved Wall Function Method for Hypersonic Reacting Turbulent Boundary Layers

The chemical reaction and cold wall effects in hypersonic reacting turbulent boundary layers (HRTBLs) cause the failure of the existing wall function method. Therefore, this paper proposes an improved wall function method to simulate skin friction cf and wall heat flux qw in HRTBLs accurately and efficiently. Firstly, the temperature–velocity relation is extended to a generalized enthalpy–velocity relation to comprehensively involve the chemical reaction and cold wall effects. Then, a new unified velocity law of the wall for the inner layer of HRTBLs is theoretically derived. Finally, an improved wall function method is designed with the new laws of the wall. Numerical experiments of typical HRTBLs show that, compared with the existing wall function method, the improved wall function method can significantly reduce the errors of cf and qw from 8.0% and 10.2% to 0.4% and 0.5%, respectively, when the near-wall grids are relaxed to the viscous sublayer, while from 11.0% and 15.3% to 1.2% and 5.8%, respectively, when the near-wall grids are further relaxed to the logarithmic layer, bringing 2.7 and 15 times enhancement of the simulation efficiency. Moreover, by introducing the reference point, the improved wall function method removes the boundary layer edge quantities while ensuring accurate results.

Genetic characterization of candidate ecdysteroid kinases in Drosophila melanogaster.

Ecdysteroids are major hormones in insects and control molting, growth, reproduction, physiology, and behavior. The biosynthesis of ecdysteroids such as 20-hydroxyecdysone (20E) from dietary sterols is well characterized, but ecdysteroid catabolism is poorly understood. Ecdysteroid kinases (EcKs) mediate the reversible phosphorylation of ecdysteroids, which has been implicated in ecdysteroid recycling during embryogenesis and reproduction in various insects. However, to date, only 2 EcK-encoding genes have been identified, in the silkworm Bombyx mori and the mosquito Anopheles gambiae. Previously, we identified 2 ecdysteroid kinase-like (EcKL) genes-Wallflower (Wall) and Pinkman (pkm)-in the model fruit fly Drosophila melanogaster that are orthologs of the ecdysteroid 22-kinase gene BmEc22K. Here, using gene knockdown, knockout, and misexpression, we explore Wall and pkm's possible functions and genetically test the hypothesis that they encode EcKs. Wall and pkm null mutants are viable and fertile, suggesting that they are not essential for development or reproduction, whereas phenotypes arising from RNAi and somatic CRISPR appear to derive from off-target effects or other artifacts. However, misexpression of Wall results in dramatic phenotypes, including developmental arrest, and defects in trachea, cuticle, and pigmentation. Wall misexpression fails to phenocopy irreversible ecdysteroid catabolism through misexpression of Cyp18a1, suggesting that Wall does not directly inactivate 20E. Additionally, Wall misexpression phenotypes are not attenuated in Cyp18a1 mutants, strongly suggesting that Wall is not an ecdysteroid 26-kinase. We hypothesize that the substrate of Wall in this misexpression experiment and possibly generally is an unknown, atypical ecdysteroid that plays essential roles in Drosophila development, and may highlight aspects of insect endocrinology that are as-yet uncharacterized. We also provide preliminary evidence that CG5644 encodes an ecdysteroid 22-kinase conserved across Diptera.

Mining Candidate Genes for Leaf Angle in Brassica napus L. by Combining QTL Mapping and RNA Sequencing Analysis.

Leaf angle (LA) is an important trait of plant architecture, and individuals with narrow LA can better capture canopy light under high-density planting, which is beneficial for increasing the overall yield per unit area. To study the genetic basis and molecular regulation mechanism of leaf angle in rapeseed, we carried out a series of experiments. Quantitative trait loci (QTL) mapping was performed using the RIL population, and seven QTLs were identified. Transcriptome analysis showed that the cell wall formation/biogenesis processes and biosynthesis/metabolism of cell wall components were the most enrichment classes. Most differentially expressed genes (DEGs) involved in the synthesis of lignin, xylan, and cellulose showed down-regulated expression in narrow leaf material. Microscopic analysis suggested that the cell size affected by the cell wall in the junction area of the stem and petiole was the main factor in leaf petiole angle (LPA) differences. Combining QTL mapping and RNA sequencing, five promising candidate genes BnaA01G0125600ZS, BnaA01G0135700ZS, BnaA01G0154600ZS, BnaA10G0154200ZS, and BnaC03G0294200ZS were identified in rapeseed, and most of them were involved in cell wall biogenesis and the synthesis/metabolism of cell wall components. The results of QTL, transcriptome analysis, and cytological analysis were highly consistent, collectively revealing that genes related to cell wall function played a crucial role in regulating the LA trait in rapeseed. The study provides further insights into LA traits, and the discovery of new QTLs and candidate genes is highly beneficial for genetic improvement.

Resistance and speed penalty of a naval ship with hull roughness

Hull roughness, attributed to factors such as corrosion, the degradation of marine coatings, and, notably, biofouling colonisation, leads to increased fuel consumption, thus entailing significant environmental and economic penalties. While this issue on commercial ships is well documented in recent studies, the specific impact on the speed of warships has received limited attention. To fill this gap, this research quantifies the resistance and power penalties, as well as the speed reduction under various fouling scenarios, and explores the resultant changes in flow characteristics around the hull. For this purpose, full-scale simulations of a naval ship, specifically the DTMB 5415, utilise the unsteady Reynolds Averaged Navier-Stokes (URANS) method. A modified wall function model was incorporated into the numerical model to accurately simulate the effects of surface roughness.

Long-term evolution of soil quality in citrus orchard terrace system: A whole life cycle perspective

Terracing is widely recognized as an effective strategy for mitigating soil erosion and preserving soil quality. This study aimed to evaluate the variations in soil aggregate C, N, and P composition, as well as the soil quality index (SQI), in subtropical citrus orchards of different plantation ages (PA) and across various terrace positions (TP). Surface soil samples (0–20 cm) were collected from four TP categories: terrace wall (TW), slub ditch (SD), under grove (UG), and between grove (BG), across varying PA (5, 15, 25, 35, and 45 years). The results showed the C, N, and P concentrations in most soil aggregates, along with the SQI of the slub ditch and under grove, increased significantly with plantation age. Compared to the 5-year-old plantations, the SQI of the slub ditch and under grove increased by 84 % and 66 % at 45 years, respectively. The aggregate stability and SQI of BG generally trended upwards but declined at 25 and 35 years. By 45 years, the SQI of the terrace wall was significantly lower than that of other positions, being 58 %, 61 %, and 39 % lower compared to the slub ditch, under grove, and between grove, respectively. Additionally, the C/P and N/P ratios of the terrace wall were higher than those of other positions, indicating phosphorus limitation in TW. Path analysis revealed plantation ages had greater effects on SQI. Aggregate stability and soil properties showed significant positive impacts on SQI. Overall, as plantation age increased, the differences in SQI among the slub ditch, under grove, and between grove decreased, while the terrace wall exhibited the weakest erosion resistance. Therefore, efforts should be made to restore the ecological function of the terrace wall, such as by colonizing it with moss. Additionally, reasonable tillage plans, including appropriate fertilization, should be formulated to enhance orchard soil quality.

CFD assessment of internal Vapor/Liquid separator in an ebullated bed reactor (EBR) for heavy oil hydroprocessing

The ebullated-bed reactor (EBR) is an important system used in the upgrading of heavy oil residue into valuable light products in petroleum refinery operations. The assessment of the gas separation region hydrodynamics is very significant to investigate the performance of EBR. An advanced understanding of EBR fluid dynamics will help in improving the design of existing and future commercial units. For this reason, the development of a computational fluid dynamics (CFD) model is very challenging, where understanding the fundamentals of fluid dynamics in EBR is carried out using a three dimensional model and the turbulence model with a standard wall function in cup geometric design. The two models were used to analyze the influence of operational parameters such as recycle ratio, and inlet velocity on gas fraction recycled and separation efficiency. Moreover, the prediction of the regime transitions occurring in the freeboard region of the EBRs was achieved using the two aforementioned models. The results of the fluid dynamics behavior revealed that the inlet velocity has a substantial effect on gas fraction recycled and separation efficiency. The liquid mean residence time scale provided a valuable efficiency result for the separation within the range of expected mean residence times. This investigation, therefore, provided a good framework for the evaluation of future design and gave a better understanding of gas and liquid flow patterns in EBR.

Roughness constant selection for atmospheric boundary layer simulations using a k-ω SST turbulence model within a commercial CFD solver

Transit of an atmospheric boundary layer (ABL) profile within computational fluid dynamics (CFD) simulations is often hindered through unintended streamwise gradients in the flow resulting in ABL inhomogeneity. Within Reynolds-Averaged Navier–Stokes (RANS) turbulence modeling in Ansys Fluent, user-defined wall functions are not available for the k–ω class of RANS models as a remedy to this problem. Instead, the practitioner is required to use the sand–grain roughness property for ground surface roughness calibration, and specify a roughness height and roughness constant, Cs, accordingly. To-date, no clear guidance on their selection is available that can accommodate both high and low roughness terrains. To overcome this, a straightforward and practical calculation is presented for the roughness constant based on the standard wall function implementation. When this calculation is synthesized with other best-practice guidelines, it is possible to reliably model transiting ABL profiles based on wind-tunnel data whilst minimizing effects due to ABL inhomogeneity.

Pit builders are assisted by walls to find suitable sites for pit construction but are slowed down by obstacles and their initial distance from the destination

Abstract Habitat selection plays a critical role in the survival and reproduction of animals, with implications for all important behaviours. Animals are often limited in their familiarity with their habitat and rely on their senses and the habitat structure to detect suitable sites to settle in. We focus here on a trap‐building predator, the wormlion, which constructs pitfall traps in loose soil, and examine how the distance from suitable microhabitats and the presence of obstacles affect its habitat selection. We conducted four experiments. Experiment 1 assessed the impact of distance on the probability of wormlions reaching a suitable microhabitat. Experiment 2 examined the interaction between distance and obstacles. Experiment 3 investigated the influence of walls on the probability of reaching destinations. Experiment 4 evaluated walls as either leading paths or barriers. Our results showed that increasing distance from the destination negatively affected the probability of wormlions reaching it, with larger individuals more likely to cover greater distances. Obstacles interacted with distance, generally decreasing movement when present. Walls positively influenced orientation, aiding wormlions in reaching suitable sites, either by following the wall or locating the destination along the wall. The function of walls varied, sometimes facilitating movement and sometimes decreasing it, depending on their orientation and context. These findings suggest that walls may serve as navigational aids for wormlions in urban environments, assisting them in locating suitable microhabitats. This has implications for understanding habitat selection in urban ecosystems. Future research should explore the long‐term effects of walls on wormlion survival and habitat quality in more natural settings.

Biocontrol potential and growth-promoting effect of endophytic fungus Talaromyces muroii SD1-4 against potato leaf spot disease caused by Alternaria alternata

BackgroundAlternaria alternata is the primary pathogen of potato leaf spot disease, resulting in significant potato yield losses globally. Endophytic microorganism-based biological control, especially using microorganisms from host plants, has emerged as a promising and eco-friendly approach for managing plant diseases. Therefore, this study aimed to isolate, identify and characterize the endophytic fungi from healthy potato leaves which had great antifungal activity to the potato leaf spot pathogen of A. alternata in vitro and in vivo.ResultsAn endophytic fungal strain SD1-4 was isolated from healthy potato leaves and was identified as Talaromyces muroii through morphological and sequencing analysis. The strain SD1-4 exhibited potent antifungal activity against the potato leaf spot pathogen A. alternata Lill, with a hyphal inhibition rate of 69.19%. Microscopic and scanning electron microscope observations revealed that the strain SD1-4 grew parallel to, coiled around, shrunk and deformed the mycelia of A. alternata Lill. Additionally, the enzyme activities of chitinase and β-1, 3-glucanase significantly increased in the hyphae of A. alternata Lill when co-cultured with the strain SD1-4, indicating severe impairment of the cell wall function of A. alternata Lill. Furthermore, the mycelial growth and conidial germination of A. alternata Lill were significantly suppressed by the aseptic filtrate of the strain SD1-4, with inhibition rates of 79.00% and 80.67%, respectively. Decrease of leaf spot disease index from 78.36 to 37.03 was also observed in potato plants treated with the strain SD1-4, along with the significantly increased plant growth characters including plant height, root length, fresh weight, dry weight, chlorophyll content and photosynthetic rate of potato seedlings.ConclusionThe endophyte fungus of T. muroii SD1-4 isolated from healthy potato leaves in the present study showed high biocontrol potential against potato leaf spot disease caused by A. alternata via direct parasitism or antifungal metabolites, and had positive roles in promoting potato plant growth.

Isolated cassava cells: Comparison of structure and physicochemical properties with starch and whole flour

Individual cells are the smallest units of the plant tissue structure, and their structure and physicochemical properties are essential for whole food processing. In this study, cassava cells were isolated using acid-alkali, hydrothermal, and pectinase methods, and the differences in microstructure and physicochemical properties among the cells, starch, and whole flour were investigated. Cassava cells isolated using pectinase showed intact individual cells with a higher isolation rate and less damage to the cell wall structure and intracellular composition. The presence of cell walls in intact individual cells inhibited the swelling and leaching of starch, resulting in a lower peak viscosity and higher gelatinization temperature than those of starch. The intact cell structure and non-starch composition enhanced the shear resistance of the gels in the sample. Heat treatment led to the gelatinization of intracellular starch and increased the permeability of the cell wall, destroying the physical barrier function of the cell wall; however, the compact cell matrix and non-starch components can inhibit starch hydrolysis. This study suggests that cells isolated using pectinase can be used to investigate the effect of cell walls on the functional properties of intracellular starch in cassava. The isolated cells provide new insights into the cassava industry.

Biomechanical effects of hemin and sildenafil treatments on the aortic wall of chronic-hypoxic lambs.

Introduction: Gestation under chronic hypoxia causes pulmonary hypertension, cardiovascular remodeling, and increased aortic stiffness in the offspring. To mitigate the neonatal cardiovascular risk, pharmacological treatments (such as hemin and sildenafil) have been proposed to improve pulmonary vasodilation. However, little is known about the effects of these treatments on the aorta. Therefore, we studied the effect of hemin and sildenafil treatments in the aorta of lambs gestated and raised at highlands, thereby subjected to chronic hypoxia. Methods: Several biomechanical tests were conducted in the descending thoracic aorta (DTA) and the distal abdominal aorta (DAA), assessing 3 groups of study of hypoxic animals: non-treated (Control) and treated either with hemin or sildenafil. Based on them, the stiffness level has been quantified in both zones, along with the physiological strain in the unloaded aortic duct. Furthermore, a morphological study by histology was conducted in the DTA. Results: Biomechanical results indicate that treatments trigger an increment of axial pre-stress and circumferential residual stress levels in DTA and DAA of lambs exposed to high-altitude chronic hypoxia, which reveals a vasodilatation improvement along with an anti-hypertensive response under this characteristic environmental condition. In addition, histological findings do not reveal significant differences in either structure or microstructural content. Discussion: The biomechanics approach emerges as a valuable study perspective, providing insights to explain the physiological mechanisms of vascular function. According to established results, alterations in the function of the aortic wall may not necessarily be explained by morphostructural changes, but rather by the characteristic mechanical state of the microstructural components that are part of the studied tissue. In this sense, the reported biomechanical changes are beneficial in mitigating the adverse effects of hypobaric hypoxia exposure during gestation and early postnatal life.

Implementation and validation of a generalized wall stress function

The generalized wall function by Shih et al. [Report No. M-1999-209398 (1999)], which accounts for non-equilibrium effects by the presence of favorable and adverse pressure gradients in turbulent flows, is addressed with the aim of performing high Reynolds number large-eddy simulations of the wall-bounded flow. The model uses a corrected law of the wall with a pressure gradient contribution to approximate the wall stress and applies to the entire viscous layer, buffer layer, and inertial region. A fully developed channel flow is first tested to validate the solver and model implementation, and then the wall function is assessed for the flow over a periodic hill. Wall-resolved simulations are in good agreement with reference results. A priori investigation with own experimental results corroborates the mathematical form of the model and suggests using different coefficients. The wall-modeled simulations show that the implemented wall model is able to improve the wall shear stress predictions compared to a standard equilibrium wall model. It corrects the underestimation of wall shear stresses by equilibrium models in the favorable pressure gradient region and the overestimation of wall shear stresses in the adverse pressure gradient region. The positions of the separation and reattachment points are also in good agreement with reference results. Furthermore, the prediction of the wall shear stress maximum in the favorable pressure gradient zone at the windward side of the hill is quite robust against coarsening the wall-normal grid spacing.

Analysis of spatiotemporal changes mechanism of cell wall biopolymers and monosaccharide components in kiwifruit during Botryosphaeria dothidea infection

To further reveal the interaction mechanism between plants and pathogens, this study used confocal Raman microscopy spectroscopy (CRM) combined with chemometrics to visualize the biopolymers distribution of kiwifruit cell walls at different infection stages at the cellular micro level. Simultaneously, the changes in the content of various monosaccharides in fruit were studied at the molecular level using high-performance liquid chromatography (HPLC). There were significant differences in the composition of various nutrient components in the cell wall structure of kiwifruit at different infection times after infection by Botryosphaeria dothidea. PCA could cluster samples with infection time of 0–9 d into different infection stages, and SVM was used to predict the PCA classification results, the accuracy >96 %. Multivariate curve resolution-alternating least squares (MCR-ALS) helped to identify single substance spectra and concentration signals from mixed spectral signals. The pure substance chemical imaging maps of low methylated pectin (LMP), high methylated pectin (HMP), cellulose, hemicellulose, and lignin were obtained by analyzing the resolved concentration data. The imaging results showed that the lignin content in the kiwifruit cell wall increased significantly to resist pathogens infection after the infection of B. dothidea. With the development of infection, B. dothidea decomposed various substances in the host cell walls, allowing them to penetrate the interior of fruit cells. This caused significant changes in the form, structure, and distribution of various chemicals on the fruit cell walls in time and space. HPLC showed that glucose was the main carbon source and energy substance obtained by pathogens from kiwifruit during infection. The contents of galactose and arabinose, which maintained the structure and function of the fruit cell walls, decreased significantly and the cell wall structure was destroyed in the late stage of pathogens infection. This study provided a new perspective on the cellular structure changes caused by pathogenic infection of fruit and the defense response process of fruit and provided effective references for further research on the mechanisms of host-pathogen interactions in fruit infected by pathogens.

Injectable Hydrogels in Cardiovascular Tissue Engineering.

Heart problems are quite prevalent worldwide. Cardiomyocytes and stem cells are two examples of the cells and supporting matrix that are used in the integrated process of cardiac tissue regeneration. The objective is to create innovative materials that can effectively replace or repair damaged cardiac muscle. One of the most effective and appealing 3D/4D scaffolds for creating an appropriate milieu for damaged tissue growth and healing is hydrogel. In order to successfully regenerate heart tissue, bioactive and biocompatible hydrogels are required to preserve cells in the infarcted region and to bid support for the restoration of myocardial wall stress, cell survival and function. Heart tissue engineering uses a variety of hydrogels, such as natural or synthetic polymeric hydrogels. This article provides a quick overview of the various hydrogel types employed in cardiac tissue engineering. Their benefits and drawbacks are discussed. Hydrogel-based techniques for heart regeneration are also addressed, along with their clinical application and future in cardiac tissue engineering.

Study on the deposition characteristics of fine particles at local components in air conditioning ventilation ducts

Air conditioning ventilation ducts are widely used in contemporary buildings. The change of airflow direction in the ducts local components can easily lead to the deposition of particles, which can easily form a secondary source of indoor air pollution and have an adverse effect on human health. Based on this, this paper utilizes the existing experimental data to validate the numerical simulation. The Reynolds stress turbulence model combined with the method of enhanced wall function was used to investigate the deposition characteristics of fine particles in different local components. For the first time, local deposition rates and deposition hotspots were proposed to analyze the simulation results. The results show that the local deposition rate of the particles with a particle size of 1μm do not differ much on each wall surface, and the particles are deposited more uniformly on each wall at the local components, with a difference of less than 10 %, and the maximum local deposition rate is on the outer wall of the local components. When the particle size is larger than 10μm, the local deposition rate on the outer wall of the local component increases significantly, with a maximum increase of 23.3 % (compared to 5μm particles), and the maximum local deposition rate increases slowly with increasing air velocity, with a maximum increase of less than 8 %. The effect of increasing particle size on the maximum local deposition rate is much greater than the increase in air velocity. With the increase of air velocity and particle size, the deposition hotspots of both the 90° bend and the T-type tee duct migrate to the middle of the wall, and the deposition hotspots of the 4-way duct migrate to the inside of the wall.

A validated numerical methodology for flow-induced vibration of a semi-spherical end cantilever rod in axial flow

This study presents a simulation method for turbulent flow-induced vibrations of cantilever rods with a semi-spherical end exposed to axial flow, a configuration investigated for the first time. This simulation strategy has been developed using solids4Foam, a toolkit for the open-source package OpenFOAM, which uses the finite-volume approach. The fluid and solid domain equations are solved separately. Coupling is achieved with the Interface Quasi-Newton Inverse Least-Squares (IQN-ILS) algorithm. The mean flow is described by the unsteady Reynolds-averaged Navier–Stokes equations. Turbulence is modeled through either the stress-transport model of Launder, Reece, and Rodi or the effective-viscosity k–ω shear stress transport model, both with the wall-function approach accounting for near-wall turbulence. The methodology is validated using experimental data produced during this study. The simulations show good agreement with the measured values of the oscillation amplitude and frequency for both flow directions (toward rod free-end and away from it). Turbulence model comparisons show that (a) Reynolds stress transport models are necessary to reproduce the vibration amplitude and (b) wall functions enable the simulations to be completed in realistic time scales. The significance to the fluid–solid-interaction (FSI) process of a so far overlooked (with the exception of a couple of recent studies) dimensionless number, the ratio of the flow dynamic pressure to the rod's Young's modulus of elasticity, is also explored. Simulations, which decouple the variation of this dimensionless number from that of the Reynolds number, demonstrate this number's strong effect on the vibration amplitude. This finding is important to the contact of further FSI studies and the scaling of FSI data.

SYSTEMATIC REVIEW ON THE EPIDEMIOLOGY AND CLINICAL MANIFESTATIONS OF VARICOSE VEIN DISEASE

This article examines the management of varicose vein disease, a condition affecting lower limbs and characterized by swollen, convoluted veins. It highlights that prolonged standing and obesity, particularly in older adults, increase the likelihood of varicose vein disease. It provides a comprehensive analysis of treatment options and preventative strategies. The review discusses varicose veins, their causes, prevention methods, risk factors, and treatments. It highlights the effectiveness of endovascular, surgical, and herbal therapies in improving quality of life and reducing secondary vein-related issues. Lifestyle interventions like consistent yoga and certain fruits and vegetables are also emphasized as preventative strategies. The article emphasizes the importance of antioxidant medications, particularly flavonoid-based ones, in reducing arterial blood pressure and preventing atherosclerosis in patients with varicose veins. These veins, typically found in the thigh or calf, are enlarged due to sensitivity to the venous wall and abnormal valve function. Over time, they may become longer, twisted, pouched, and thicker due to gravity pulls.

Investigation of resistance performance of anti-icing wave-plate separators for marine gas turbines intake system

Abstract Due to their high power and efficiency, gas turbines are commonly used propulsion systems in hovercraft propulsion systems. In polar and cold marine environments, when a hovercraft rises, a significant number of droplets are generated on the water surface and are drawn into the gas turbine’s air intake with the cold air. This paper takes the structure of the original wave-plate separator as a reference and designs two structures: the rhombic anti-icing wave-plate separator (RAWS) and the streamlined anti-icing wave-plate separator (SAWS). Experimental and numerical simulation methods are employed to calculate the air intake resistance of the two structures at speeds ranging from 1 to 10 m/s. The results show that the K-ε standard enhanced wall function turbulent model is the closest to experimental measurements, with all calculated results having an error below 5%, demonstrating reliability. Compared to RAWS, the calculated total pressure loss for the SAWS structure decreases by 200 Pa under a designed air intake velocity of 7 m/s, representing a relative reduction of 40.8%. This provides a valuable reference for the design and resistance optimization of ship air intake anti-icing devices.