Cross-sectional Shape Research Articles

3D concrete printing using computational fluid dynamics: Modeling of material extrusion with slip boundaries

This paper investigates the role of slip boundary conditions in computational fluid dynamics modeling of material extrusion and layer deposition during 3D concrete printing. The mortar flow governed by the Navier-Stokes equations was simulated for two different slip boundary conditions at the extrusion nozzle wall: no-slip and free-slip. The simulations were conducted with two constitutive models: a generalized Newtonian fluid model and an elasto-viscoplastic fluid model. The cross-sectional shapes of up to three printed layers were compared to the experimental results from literature for different geometrical- and speed-ratios. The results reveal that employing free-slip boundary conditions at the extrusion nozzle wall improves layer-mimicking quality for both constitutive models, indicating the presence and importance of a lubricating layer of fine particles at the concrete-solid wall interface. This enhanced performance is primarily due to the observed decrease in extrusion pressure that minimizes layer height- and width-deviations compared to the experimental prints. Furthermore, the free-slip boundary conditions play an important role in predicting the multilayer prints, its deformation and groove shapes.

Assessment of the force characteristics of dispersion of collagen-containing materials with a new single-sided cutting tool of impact-cutting action

The design of a one-sided cutting tool and a new method of vibrational dimensional dispersion of waste of collagencontaining materials are developed. Hodographs and cross-section shapes are constructed using computer modeling of complex spatial vibration movements of the cutting part of the tool. The possibilities of controlling of the geometry of cut chips are determined. Expressions are obtained for calculating of the cutting force during chip separation and the dependence of the cutting force on the angular speeds of the complex movement of the tool. Keywords:impact cutting tool, elastic-visco-plastic material, leather waste, reprocessing, cutting force, crushing, modeling, chip control, dimensional vibration dispersion sergeev-sv@list.ru

Influence of Interior Column on the Behaviour of Quasi-Rectangular Tunnel

The growing population in major cities around the world requires significant development of transportation infrastructure, especially underground system. It requires the construction of more subway lines, and larger tunnel cross-sections. In underground construction, a cross-sectional shape which is a combination of circular and rectangular tunnels is an advanced trend. This shape incorporates the advantages of both forms. There are two terminologies used to classify these shapes, including sub-rectangular and quasi-rectangular tunnels. While the sub-rectangular tunnel lacks an interior column, the quasi-rectangular tunnel includes an interior column located at the center of tunnel. Recent studies focus on separately investigating the behavior of sub-rectangular and quasi-rectangular tunnels using various methods such as numerical methods, analytical methods, and experimental methods. The present study conducted a numerical comparison of these two types of tunnels. The results indicated that the presence of an interior column help to increase the stability of the lining structure. The internal forces within the quasi-rectangular tunnel with an interior column are smaller than those of the sub-rectangular tunnel and quasi-rectangular tunnel without an interior column.

Numerical investigation on thermal-hydraulic performance of variable cross section printed circuit heat exchanger

CO2 transcritical power cycle (CTPC) systems have attracted considerable research focus in the fields of thermoelectric conversion and waste heat recovery. The regenerator is a key component affecting the CTPC system's efficiency. To improve the comprehensive performance of the regenerator, extensive research has been conducted to optimize the regenerator flow channel design. However, the optimization of the traditional Z-channel printed circuit heat exchanger structure (ZPCHE) is limited to constant cross-sectional configurations along the flow direction, which can lead to low channel space utilization. To solve this problem, an efficient variable cross section Z-channel structure (UAPCHE) is proposed in this study. The structure is designed with different cross-sectional shapes along the flow direction to fit the flow path of the main fluid. UAPCHE achieves a coordinated optimization of the heat transfer (Nu), flow (dP), and compactness performance (Q/V) by increasing the effective utilization of the channel space and weakening the damage to the fluid boundary layer. The design principle of the UAPCHE is introduced, and based on this, the structural parameters of the UAPCHE are optimized to achieve the best comprehensive performance. The results show that, compared with the ZPCHE, Nu of UAPCHE can be increased by 16.79%, dP can be reduced by 19.48%, and Q/V can be increased by 22.65%.

Asymptotic Study of Flows Induced by Oscillations of Cylindrical Bodies

Hydrodynamic flows induced by translational oscillations of cylindrical bodies of various cross-sectional shapes are studied. The motion of fluid around oscillating bodies is described using the system of Navier–Stokes equations written in a generalized curvilinear coordinate system. Transition to a given body shape is implemented using a conformal mapping. The problem is solved using the method of successive asymptotic expansions under the assumption that the oscillation amplitudes are small. In each asymptotic approximation, the subproblems are solved numerically using the finite-difference method. Based on the results of the work, estimates of the hydrodynamic effect are obtained, the applicability of the high-frequency asymptotic approximation is estimated, and secondary stationary flows near cylinders are studied, in particular, the occurrence of directed stationary flows near an oscillating asymmetric body is considered with reference to the Joukowski airfoil.

Wake steering of wind turbine in the presence of a two-dimensional hill

Wake interference between turbines in wind farms can lead to significant losses in the overall power output from farms. Wake steering is a strategy in which yaw is introduced in the upstream turbines with respect to the incoming flow field to reduce wake interference with downstream turbines. To characterize the effectiveness of wake steering for turbines located on a hilly terrain, an open source simulator for wind farm applications has been used to perform large eddy simulations (LESs) of a 5 megawatt (MW) wind turbine located at the base of a sinusoidal hill. The height and length of the hill, as well as the turbine yaw angle, are systematically varied over a series of 10 simulations in which inflow corresponds to the neutral atmospheric boundary layer. Results from the LES statistics show that, for a given yaw angle, the power output from the turbine is determined primarily by the height of the hill, rather than the length of the hill. The magnitude of the centerline wake deficit and equivalent wake radius are reduced due to the presence of hills and are not very sensitive to the yaw angle. The theoretical prediction of the wake recovery appears to qualitatively agree with the LES statistics. The yaw-induced spanwise wake deflection is not affected by the hill height significantly. Streamwise vorticity distribution within the lower half of the wake intensifies due to the presence of strong mean velocity gradients present near the surface of the hill, which, in turn, leads to a reduction in the distortion of the shape of a wake deficit cross section.

IMAGE PROCESSING APPROACH FOR FOREIGN MATERIAL DETECTION IN COTTON BUNDLE

The image processing philosophy is mainly determined by the complexity of the image and provides the necessary information to be derived from the image. In the textile industry, the image processing technique focuses on the determination of the geometric properties of the fibers such as cross-sectional shape, diameter, length, fineness, and curl while the studies on the yarn characteristics mostly focus on the determination of yarn hairiness, yarn unevenness and yarn defects (thick place, thin place and neps). In this study, previous studies about image processing approaches that are applied for fiber characteristics were investigated. A case study was conducted to automatically determine the visible foreign matter in the waste cotton bundle that can be used for recycled cotton yarn production. It was revealed that the image processing methods can be successfully applied for foreign fiber and matter detection in cotton bundle. As a result, it is emphasized that the waste cotton properties can be specified with a sensitive and accurate approach via image processing technique, objective and numerical determination can be obtained instead of visual evaluation based on experience.

Modeling of ontogenetic changes in the shell cross section of the most ancient (Late Permian) representatives of <i>Otoceras</i> (Ammonoidea)

For the first time, shell cross-sections were made for the most ancient (Late Permian) representatives of the genus Otoceras. From these cross-sections, ontogenetic changes in the shell shape of O. concavum Tozer were reconstructed at size stages ranging from tiny to very large. A moderately wide shell with a moderately narrow umbilicus narrows intensely to its tiny size, becoming a narrow shell. At the stage of very small size, the shell expands, again becoming moderately wide, and the umbilicus narrows slightly, remaining moderately narrow. However, at small sizes, the change in these characteristics occurs in the same direction, but with increased intensity. Moreover, important changes are observed at the medium-sized stage, when the expansion of the shell stops and the umbilicus becomes narrow. At the end of the studied ontogenesis, the morphological development of the mollusk was aimed at the formation of a moderately narrow shape with a very narrow umbilicus. Of the variety of shell shapes previously established among ammonoids, numbering 35 types, representatives of the species O. concavum throughout the studied ontogenesis had only three: subdiscocone, tumaricone, and pachycone. Finally, the constructed ontogenetic model clearly demonstrated the features of the development of the cross-sectional shape of O. concavum shells during their growth, emphasizing ontogenetic trends in changes in the most important parameters of the shell. We conclude that the identified transformations of the shell shape contribute to the diagnosis of small-sized Otoceras, and can serve as the basis for the subsequent reconstruction of the morphogenetic development of the family Otoceratidae.

Modern developments in burn wound dressing

Purpose Intense interest has been shown in creating new and effective biocide agents as a result of changes in bacterial isolates, bacterial susceptibility to antibiotics, an increase in patients with burns and wounds and the difficulty of treating infections and antimicrobial resistance. Woven, nonwoven and knitted materials are used to make dressings; however, nonwoven dressings are becoming more popular because of their softness and high absorption capacity. Additionally, textiles have excellent geometrical, physical and mechanical features including three-dimensional structure availability, air, vapor and liquid permeability, strength, extensibility, flexibility and diversity of fiber length, fineness and cross-sectional shapes. It is necessary to treat every burn according to international protocol and along with it has to focus on particular problems of patients and the best possible results. Design/methodology/approach The objective of this paper is to conduct a thorough examination of research pertaining to the utilization of textiles, as well as alternative materials and innovative techniques, in the context of burn wound dressings. Through a critical analysis of the findings, this study intends to provide valuable insights that can inform and guide future research endeavors in this field. Findings In the past years, there have been several dressings such as xeroform petrolatum gauze, silver-impregnated dressings, biological dressings, hydrocolloid dressings, polyurethane film dressings, silicon-coated nylon dressings, dressings for biosynthetic skin substitutes, hydrogel dressings, newly developed dressings, scaffold bandages, Sorbalgon wound dressing, negative pressure therapy, enzymatic debridement and high-pressure water irrigation developed for the fast healing of burn wounds. Originality/value This research conducts a thorough analysis of the role of textiles in modern burn wound dressings.

Seepage propagation simulation of a tunnel gasketed joint using the cohesive zone model

The gasketed joint plays a critical role in the waterproof or water-leakage resistance performance of tunnel segmental linings. This study presents a novel numerical simulation method based on the cohesive zone model (CZM) to accurately analyze the seepage phenomena along the interface of elastic sealing gaskets in shield tunnel joints. While traditional finite element methods are widely used, they cannot simulate interface opening, limiting their applicability. To overcome this challenge, the proposed method leverages the concept of hydraulic fracturing and redefines the seepage problem as a seepage problem of elastic impermeable media. By establishing a two-dimensional hydraulic fracturing model using the CZM, this study conducts a comprehensive sensitivity analysis of the cohesive element parameters and validates the accuracy and effectiveness of simulating seepage along the interface of elastic impermeable media. Based on the insights gained from the sensitivity analysis, a seepage calculation model is successfully developed, considering the unique characteristics of elastic sealing gaskets. The model is applied to three cross-sectional shapes of elastic sealing gaskets, and their seepage characteristics are analyzed based on the interface opening displacement and liquid pressure distributions during seepage. The results highlight the SC3 cross-sectional shape, which exhibits minimal opening displacement and the highest net water pressure at the moment of seepage occurrence, demonstrating superior waterproof performance compared to other forms. Through the introduction of the CZM, comprehensive parameter analysis, validation, and practical application, this study overcomes the limitations of traditional finite element methods in simulating interface opening. The proposed model, which more accurately captures seepage characteristics than other methods, provides an optimized simulation method for analyzing hydraulic coupling issues related to seepage at shield tunnel joints and is a significant contribution to the field, enhancing our understanding and enabling more accurate analyses of seepage phenomena in shield tunnel joints using elastic sealing gaskets.

Dynamic Pore Network Modeling of Imbibition in Real Porous Media with Corner Film Flow.

Wetting films can develop in the corners of pore structures during imbibition in a strongly wetting porous medium, which may significantly influence the two-phase flow dynamics. Due to the large difference in scales between main meniscus and corner film, accurate and efficient modeling of the dynamics of corner film remains elusive. In this work, we develop a novel two-pressure dynamic pore network model incorporating the interacting capillary bundle model to analyze the competition between the main meniscus and corner film flow in real porous media. A pore network with four-point star-shaped pore bodies and throat bonds is extracted from the real porous medium based on the pore shape factor and pore cross-sectional area, which is then decomposed into several layers of sub-pore networks, where the first layer of sub-pore network simulates the main meniscus flow while the upper layers characterize the corner film flow. The two-phase flow conductance of throat bonds for different layers of sub-pore networks are determined by high-resolution two-phase lattice Boltzmann modeling, thus inherently considering the viscous coupling effect. In addition, two artificial neural network models are developed to predict the two phases' flow conductance based on the shape of the throat cross section and the fluid properties. The accuracy of the developed model is validated with a lattice Boltzmann simulation of imbibition in a strongly wetting square tube. Then the model is used to simulate imbibition in a strongly wetting sandstone porous medium, and the competition between the main meniscus and the corner film flow is analyzed. The results show that with decreasing capillary number and viscosity ratio between wetting and nonwetting fluids, the development of the wetting corner film becomes more significant.

Effect of the Cross-Sectional Shape on the Dynamic Response of a Cantilever Steel Beam Using Three Modal Analysis Methods

Effect of the Cross-Sectional Shape on the Dynamic Response of a Cantilever Steel Beam Using Three Modal Analysis Methods

Experimental and numerical study on the energy absorption performance of aluminum foam-filled multi-cell square tubes

When rockbursts occur, the unloading rate of the relief valve of the hydraulic support is less than the loading rate of the impact load, which leads to a continuous increase in the hydraulic column pressure or even failure. To improve the service life of hydraulic support structures under impact loading, an aluminum foam-filled multi-cell square tube is designed and investigated as an energy absorption component to prevent support column failure. In this study, the energy absorption performance of the multi-cell square tube during buckling deformation is investigated via simulation and quasi-static compression tests considering the cross-sectional shape and aluminum foam filling rate. The equivalent crushing load of the tube is calculated by analyzing the impact of the basic deformation unit. The results show that the corner-to-corner (C2C) multi-cell square tube exhibits the best energy absorption performance among six kinds of cross sections. In addition, the interaction between aluminum foam and a multi-cell square tube can improve the performance of the multi-cell square tube. Furthermore, after the C2C component is installed in the support column, the load on the column is significantly reduced, and most of the impact energy is absorbed. These results are expected to improve the performance of hydraulic supports and can be used to prevent rockbursts, which is highly important for practical engineering.

A Generalized Nonlinear Beam Element for Slender RC Members Using a Polygonization Section Approach—Part II: Verification of Analytical with Experimental Results

The proposed mathematical model, described in detail in Part I of the present paper, aims to solve the common numerical problems that currently characterize classic fiber models when used with a moderate fiber grid for reasons of computational cost. To confirm these objectives, comparisons were made between analytical predictions of the model with experimental results of RC specimens and of a 2D scaled frame for a wide range of parameters that mainly concern slender specimens without significant influence of the bond slip phenomenon, different types of cross section shapes, and various loading histories. The agreement between analytical to experimental results was found to range from very good to excellent in some cases.

Data driven models for capacity prediction of CFS lipped channel flexural members

Cold-Formed Steel (CFS) is considered as a sustainable material and CFS members are becoming popular nowadays as primary or secondary load carrying structural elements. The increasing use of CFS members is owing to their other advantages like high strength to weight ratio, versatility in cross sectional shapes and dimensions, easy fabrication and mass production, uniform quality, good energy efficiency, easiness to handle and transport etc. The behaviour of cold-formed members under flexure is complex as it involves the occurrence of various buckling modes (Local, distortional or lateral-torsional buckling) and the possible interaction between them. Although, the moment carrying capacity of CFS beams can be estimated using existing codes and design standards, the present study is an attempt to introduce an alternate rapid capacity assessment tool based on machine learning for the same. Available data on experiments conducted on CFS lipped channel beams are collected to model and analyse in ABAQUS for validating the finite element model. The validated FE model is used for developing the input-output data set for training the Machine Learning (ML) models by sampling the geometric and strength related input parameters of the CFS beam. Recently introduced machine learning regression models like Linear Regression, Lasso regression, K-Nearest Neighbors, Decision Tree, Random Forest, Adaptive Boosting, Extreme Gradient Boosting, Light Gradient Boosting, Categorical Boosting, Gradient Boosting Regressor, Support Vector Machine and Artificial Neural Network are used to predict the ultimate flexural capacity of CFS beams. The CatBoost model is emerged as the best performing algorithm for predicting the flexural capacity, with 98.5% accuracy for the test data set. A SHAP (SHapley Additive exPlanations) analysis is also conducted for the global and local interpretation of the prediction of the best performing machine learning model. SHAP results not only indicate the influence of input parameters on output prediction, but also the influence of input parameters on each other in predicting the output.

A hybrid wave and finite element/boundary element method for predicting the vibroacoustic characteristics of finite-width complex structures

This paper presents a hybrid wave and finite element/boundary element method for predicting the vibroacoustic characteristics of complex panels characterised by an irregular cross-sectional shape with a non-flat upper surface. In this approach, the panels are treated as waveguides and only a small segment of the panel is modelled using finite elements. The mass and stiffness matrices of the segment are then post-processed to project the motion onto its cross-sectional boundaries interfacing with the surrounding fluids. The acoustic pressures in the fluids are modelled by applying Fourier transforms to the Helmholtz boundary integral equations in the wavenumber domain. For each wavenumber component, the pressures acting on the segment are transformed into external nodal forces by evaluating the virtual work performed by the surface pressure on the segment. The wave and finite element formulations are subsequently coupled to the discretised boundary integral equations to determine the response of the panel to acoustic wave excitation. The hybrid method for predicting dispersion curves and sound transmission is validated through comparisons with predictions obtained from both an analytical model and a wave-based method found in the literature. To demonstrate the practical utility of the approach, the hybrid method is employed to predict sound transmission through a corrugated sandwich panel, where developing an analytical model is difficult. The method provides accurate predictions at a low computational cost.

Exact Insulated-Tip Fin Length Correction for Tip Convection Compensation

Abstract This study details the derivation of a length correction term for computing the heat transfer performance of one-dimensional, straight, convecting-tip fins using the insulated-tip fin solution. Use of this corrected length in the insulated-tip fin solution produces the identical heat transfer rate and temperature profile as those computed using the more complex convecting-tip fin equations. The analysis derives the length correction equation from fundamental principles and produces a simple, closed-form expression valid for all fin cross-sectional shapes. Furthermore, the valid parameter range where this length correction is applicable, and outside of which no exact length correction is possible, is quantified.

Unstitching the Past: An Experimental and Microwear Investigation of Dorset (Paleo-Inuit) Needles from the Foxe Basin Region

For Paleo-Inuit cultures, needles are arguably one of the most important artefact types, as they were used to create warm, waterproof clothing that is essential for survival in Arctic environments. This, in combination with the prevalence of needles within archaeological collections, has prompted many researchers to the topic of Paleo-Inuit needles. However, the majority of their studies have approached the material using traditional, typological methodology. A pilot study conducted by Siebrecht et al. (2021) demonstrated that, while needles from several Dorset Paleo-Inuit culture (c. 800 – 1300 AD) sites in the Foxe Basin region were previously considered as typologically identical, microwear analysis highlighted variation in how they would have been made and used over time and across sites. The pilot study also noted variation, across sites, in certain typological attributes, such as needle eye shape, distal end shape, and cross-section shape. The present study aims to expand on these discoveries by considering possible reasons for variability in the attribute of needle cross-section shape. Methodologically, we use microwear analysis, experimental archaeology, and ethnographic collaboration. With this approach, we were able to explore Dorset needle making and sewing practices in more detail than has been possible in prvevious, purely typology-focused studies. Our results showed no observable pattern between cross-section shape and the material being sewn but may reveal links between needle size and the material being sewn, a correlation in different polish types and the duration of needle use, as well as insights into the possible sewing techniques used by Dorset groups. Our study thus offers a fresh perspective on this topic and points to new directions for this area of Arctic archaeological research.

Effects of cross-sectional shape on flow and heat transfer of the laminar flow of supercritical carbon dioxide inside horizontal microchannels

Supercritical carbon dioxide (sCO2) flow at the micro scale provides an excellent heat transfer solutions for a range of microelectronics cooling applications. The cross-sectional shape of the microchannel (in combination with the abruptly changing thermophysical properties of sCO2) affects the heat transfer and flow characteristics, but these effects are not well understood at constant wall temperatures as most of the previous studies were performed at constant surface heat fluxes. Current study numerically investigated, using CFD, the effects of different cross-sectional shapes, such as circle, equilateral triangle, semi-circle, and square, in zero gravity (space) and in terrestrial conditions, at constant wall temperatures.In all cases, the hydraulic diameter of the microchannel was 100 μm, the total length was 27 mm, and the heated length was 25 mm. A total of 216 cases were analyzed to predict the effects of surface temperature ranging from 310 to 330 K, pressures ranging from 8 to 10 MPa, and Reynolds numbers from 100 to 500 on the heat transfer and flow. It was revealed that the microchannel with triangular cross-section has the highest heat transfer rate, highest mass flow rate, and lowest pressure drop both in zero gravity and in terrestrial conditions. The total surface heat transfer rate for the triangular microchannel was about 49% higher than the circular microchannel at a pressure of 8 MPa, around 53% higher at 9 MPa, and about 55% higher at 10 MPa. However, the average surface heat transfer coefficient displayed a complex behavior, and it depends on the combination of surface temperature, Reynolds number, and operating pressure. The surface heat transfer rate and pressure drop were increased for all shapes at terrestrial conditions, emphasizing that the effects of buoyancy cannot be neglected. Overall, this study revealed a complex behavior of the flow of sCO2 inside microchannels of different cross-sectional shapes, and the triangular cross-section performed better than other shapes.

CFD Analysis of Pressure Drop Reduction in PEMFC Flow Channels with Distinct Cross-Section Shapes

Proton exchange membrane fuel cells (PEMFCs) have great potential to produce renewable, sustainable and clean energy and reduce air pollutants to mitigate climate change. PEMFCs consist of distinct parts including anode and cathode bipolar plates having flow channels, gas diffusion layers, catalyst layers, and membrane. The flow channel geometry influences the flow and pressure drop characteristics of the channel and cell performance. In this work, a three-dimensional (3D) CFD model is built employing SOLIDWORKS and ANSYS Workbench. The innovative configurations are generated by changing the half of 0.2 x 0.2 mm square channel to 0.3 x 0.1 mm, 0.3 x 0.15 mm, 0.3 x 0.2 mm and 0.3 x 0.25 mm rectangular section at the top. The results showed that increasing rectangular section height significantly reduced pressure drop at the anode and cathode with a slight decrease in the current density at 0.4 and 0.6 V. The new configuration with 0.2 x 0.1 mm half square section at the bottom and 0.3 x 0.25 mm rectangular section at the top decreases the current density, anode and cathode pressure drop of 11%, 69% and 58%, respectively in comparison to 0.2 x 0.2 flow channel at 0.4 V. Taking into account pressure loss along the flow channels, this configuration is a good option to improve the cell performance.