Forced Flow Research Articles

SIMMER code two-fluid model well-posedness and stability for simulating liquid metal (lead–lithium eutectic), water vapor, and non-condensable gases multi-component multi-phase flows

Liquid metals are employed as a coolant in liquid metal fast reactors (LMFR) and are considered breeders and coolants for future power-producing fusion reactors. The interaction of liquid metals with other coolants, such as air and water, is one of the possible occurrences in liquid metal-cooled reactors. Although the SIMMER-III computer code is currently in the validation and verification phase, it is a prospective candidate code for correctly investigating possible accidents. This study aims to determine the stability and well-posedness of the SIMMER-III code Eulerian-Eulerian two-fluid model (TFM) under any such accident scenario. This work also considers the influence of the virtual mass force and diffusion forces in momentum on TFM stability in accelerated liquid metal, steam, and non-condensable gaseous flows throughout all flow regimes. The characteristics method is used to assess the ill-posed nature of TFM for all types of accidents and accident scenarios in a hypothetical simplified system model with several components (Lead–Lithium, non-condensable gases, and water vapor). It has been discovered that the analysis findings vary from the air and water two-component two-phase flows (characteristics roots spectrum and error growth rate patterns) and are particularly sensitive to the diffusion and virtual mass coefficients. This is because liquid metals have a higher density than liquid water and steam, resulting in strong virtual mass forces and weak diffusion forces in liquid-metal and gas two-phase flows. Because of the extensive range of possible interactions between fluxes of different components, producing an accurate representation of diffusion in multi-component mixtures is difficult. Because of this, it is strongly suggested that the virtual mass coefficient and diffusion coefficients be handled more accurately for these kinds of flows. The values of these coefficients significantly affect how accurate proposed TFM predictions are, but there hasn't been much research on how to estimate them. The study also sheds light on the model's accuracy and highlights the areas where the model's predictions will be mathematically trustworthy.

Passive Control Measures of Wind Flow around Tall Buildings

The growth and diversification of tall buildings demands higher performance standards that encompass serviceability and resilience. In this respect, the control of air flow around tall buildings poses challenges to minimising the energy that could induce large vibrations or forces. The present investigation scrutinises the flow around a tall structure with variations on its surface roughness by adding balconies to the facade, as a form of passive control of the flow loads. This is conducted through flow simulations across optimised computational arrays that capture 3D effects. To illustrate the applicability of the proposed approach, two types of facades rotated 0∘, 90∘ and 180∘ are considered while focusing on pressure and vorticity fields. It was found that the presence of balconies produces zig-zag patterns on the face where they are located, whereas balconies on the front facade reduce drag with respect to the smooth case. Furthermore, buildings with balconies on their lateral faces experience some increase in drag force and the improvement of the aerodynamics around the lateral pedestrian zones. No qualitative variations between triangular and rectangular balconies were found, excepting some changes in pressure magnitude on the rear side induced by balconies placed on the front and rear facades. Through the comparison of results, it was confirmed that the findings align with previous studies undertaken for medium and low-rise buildings. This reinforces the proposal of using such passive control measures to improve the aerodynamic performance of tall buildings. The study enables the quantification of flow configurations and forces on the building’s faces. Some of the proposed passive control measures effectively mitigate pressure levels while causing large local disturbs on pressure and vorticity that should be attended to by designers of this type of facades.

Flow and Heat Transfer Characteristics in the Entry and Stabilized Flow Regions of a Circular Channel Rotating About a Parallel Axis

Abstract Cooling of heavy-duty electrical machines such as generators and motors is crucial for the smooth operations without thermal runaway. A commonly employed technique for the cooling of rotors in these machines is to place channels at different radial locations for the continuous passage of coolant. These channels are therefore rotating about a parallel axis, and the rotation-induced forces alter the flow and thermal behavior of the coolant compared to stationary channels. The present study reports a detailed numerical investigation on a long circular channel rotating about a parallel axis. The objective is to analyze the flow, heat transfer, and rotation-induced forces (Coriolis and centrifugal forces) in the entry region as well as in the region where flow is stable (the term ‘stable’ is used rather than ‘developed’ due to the presence of secondary flows in this region). The rotating channel was subjected to constant wall heat flux and constant wall temperature conditions at different Rotation numbers of 0, 0.15, 0.4, and 0.6. The Coriolis force is observed to be strong enough in the entry region to influence the flow. In the “stable flow” region, the centrifugal force becomes more dominant and forms counter-rotating secondary vortex pair, which causes circumferential variation in the Nusselt number. The flow and heat transfer characteristics for constant wall heat flux and wall temperature boundaries are the same for rotation conditions with similar values of rotational Grashof number. A correlation is presented for the circumferential variation of the Nusselt number in the stable flow region.

Impact of the Stefan gusting on a bioconvective nanofluid with the various slips over a rotating disc and a substance-responsive species

This paper presents thorough computational and theoretical analyses of steady forced convective flow over a rotating disc submerged in a water-based nanofluid containing microorganisms. It delves into the examination of boundary layer flow characteristics of a viscous nanofluid, considering Stefan blowing effects and multiple slip conditions influenced by a magnetic field. Notably, the study accounts for novel aspects such as thermal radiation and both constructive and destructive chemical reactions. The movement of nanoparticles is elucidated based on thermophoresis and microscopic behaviors, while changes in volume fraction do not affect the thermo-physical properties of the nanofluid. To address the altered nonlinear set of differential equations, an effective numerical approach, the Keller-Box method, is implemented for critical and efficient solutions. These appropriate transformations are defined and applied. When compared to blowing suction, it shows a better enhancement in the rate of heat transfer, mass, and microorganisms. Some of the main observations are there is a decrease in wall skin friction in the directions of radial and tangential as magnetic field strength is increased. The evaluation of thermal boundary layer thickness and temperature is noted for the radiation parameter (Rd) improvement. The present analysis has applications in electromagnetic micro-pumps and nanomechanics. As to the applications in the science and engineering fields, technologies such as micro-electromechanical systems-based microfluidic devices and microfluidic-related technologies will be accepted.

The viscous force and torque on a closed irrotational surface

The force and torque on a solid body in a viscous potential flow are often taken to be independent of viscosity. Joseph et al. (Eur. J. Mech. B/Fluids, vol. 12, 1993, pp. 97–106; J. Fluid Mech., vol. 265, 1994, pp. 1–23) proved that this holds for (i) the force (not the torque) in any two-dimensional flow, and (ii) the drag force experienced by a purely translating three-dimensional body. The remaining components of the force and torque, along with general three-dimensional flows, were not considered. Importantly, the flow was assumed to be unbounded and irrotational everywhere. We eliminate this rarely satisfied assumption and consider the viscous force and torque experienced by any closed surface where the flow is irrotational locally; this can include a body's surface. Any vorticity distribution is permitted away from the closed irrotational surface. In so doing, we complete the analysis of Joseph et al. for all components of the viscous force and torque in two and three dimensions and enable application to real flows that inevitably contain regions of vorticity.

Deformation and Plasticity of Reinforced Concrete

Statement of the problem.Development of the model of plasticity of reinforced concrete structures is based on the intensity of the "stress-strain" relation to project tensors using transitions, as well as the coefficients of the steps of forces and axes (principal angle and strain-strain, total shear strain, etc.). Results. The dependences of plasticity modulus of concrete, transverse coefficient have been obtained. Complex functions of generalized hypotheses of deplanation of linear and angular deformations and jumps for crack formation breakaway and stiffness are constructed. It includes force flows, i.e., blocks of compressed and tensile concrete for isotropic medium (the first object), "main cracks" from fracture mechanics, functional and two-cone element for the deformation effect of reinforced concrete. The resistance of the tensile concrete is transferred to the working reinforcement using the total average longitudinal and transverse forces for the transversal-isotropic environment, including the average modulus of reinforcement and the reduced tensile concrete coefficient of the second limit state group. The special dowel effect is derived from the second level model of structural mechanics for a rebar with two pinched ends, as well as crack opening (a development of the Thomas –– author hypothesis), crack-track bank shear, and buckling. The main vector of forces in the reinforcement is characterized by two values of longitudinal and transverse displacements and the width of opening and shear of the crack-track (the third object). Conclusions. The energetic theory on the surface of the sphere and the determination of the integral of the mean square value of the tangential stresses of plasticity theory allowed to develop an alternative to the ge-neral model in the form of a paraboloid by summing the volume sectors, radius-levels from the matrix of sliding planes (including octahedral and pure shear) in concrete medium from microcracks to macrocracks.

Spectral analysis of dispersed multiphase flows in the presence of fluid interfaces

Spectral analysis of dispersed two-phase flows is highly desirable to reveal the interplay of the various flow scales, much larger or much smaller than the size of the dispersed bodies. This is a challenging task as the matching conditions at the body interfaces generate singularities in the fields describing the two-phase mixture. The nature of these singularities and their consequences on the spectra are theoretically analyzed for bubble or droplet flows. Results of direct numerical simulations are reported and spatial spectra of the mixture velocity, the flow forces and their power are examined. The regular part of the spectral densities of energy production, dissipation and transfers between scales are separated from their singular part. The resulting spectral energy balance, free of the footprint of the singularities, is found in agreement with coarse-grained simulations where the interfaces are filtered out before solving the Navier–Stokes equations. These results pave the way for the spectral analysis of more complex turbulent dispersed flows.

Biomimetic porous wick with efficient fluid transport and excellent heat transfer for loop heat pipes

The porous wick, as a core component of the loop heat pipe (LHP), serves as a source of circulation power. Inspired by the transport system of plant vessels, a radially stacked polyethersulfone (PES) porous wick was designed using PES membranes with an anisotropic porous structure. The PES membranes exhibited excellent capillary force and high permeability. However, the supply capacity of the axially stacked wick was far inferior to that of sintered wick due to the problem of contact gaps and pore misalignment between layers. From the bionic point of view, a laminar winding special transport structure, which is perpendicular to the direction of liquid transport was proposed. The method effectively avoids the adverse effects of gap and pore misalignment on liquid transport. Combining experimental and simulation methods, the heat transfer characteristics and liquid transport characteristics of the radial stacking polyethersulfone wick (RPES) were studied and compared with those of traditional axial stacking polyethersulfone wick (APES) and sintered nickel wick. The results showed that the heat transfer performance of RPES-LHP was significantly improved, with the heating surface temperature maintained at 54.1 °C and thermal resistance of 0.095 °C/W under a heat load of 400 W, which was respectively 26.6 °C and 0.066 °C/W lower than that of the APES-LHP. The evaporator thermal resistance of RPES-LHP also ranked among the top in existing research on wicks. Simulation results indicated that the radial stacking method avoided capillary force weakening and flow resistance increase caused by gap and pore misalignment, thereby enhancing the supply capacity of RPES. The concept of regulating the stacking orientation of the wick to be perpendicular to the direction of liquid transport can strengthen the supply capacity and provide light on the design of porous wicks in the future.

Geometrical investigation of forced convective flows over staggered arrangement of cylinders employing constructal design

The current numerical work conducted a geometrical investigation of forced convective flows over a staggered arrangement of four cylinders applying constructal design. The main objectives are to determine designs maximizing the Nusselt number (NuD) and minimizing the drag coefficient (CD) of the cylinders at three distinct Reynolds numbers (ReD = 10, 40, and 150) considering Pr = 0.71. The problem involves two constraints: cross-sectional area of the cylinders and the occupation area of the arrangement, and three degrees of freedom: ST/D, SL1/D and SL2/D. These represent the ratios between the transversal pitch, the longitudinal pitch between the frontal and intermediate cylinders, and the longitudinal pitch between the intermediate and posterior cylinders over the diameter. The introduction of two longitudinal pitches enabled an exploration of the generation of asymmetrical patterns in the flow direction. Results indicated a strong dependency of the arrangement design on the Reynolds number. Moreover, asymmetrical configurations generally benefited both performance indicators for the present conditions. The most favorable arrangements for the fluid dynamics were achieved with the lowest ST/D, more concentrated longitudinal pitches for ReD = 10, and asymmetrical pitches for ReD = 40 and 150. Concerning the thermal purpose, the highest magnitude of ST/D and asymmetrical longitudinal pitches led to the highest NuD. For ReD = 10, the intermediate cylinders are near the upstream one; for ReD = 40 the length of the arrangement increases with the intermediate cylinders near the downstream one, and for ReD = 150, the arrangement occupied all the length of occupation area with slight asymmetry.

Simulation of enhancement techniques impact on fluid dynamics and thermal mixing of laminar forced convection flow

Simulation of enhancement techniques impact on fluid dynamics and thermal mixing of laminar forced convection flow

Ashvamedha Yagya in the Vedas

The Ashvamedha Yagya has been hailed as the monarch of rituals in the Indian tradition. Since Vedic times, the Ashvamedha holds a distinguished position among sacrificial rites. The horse symbolizes power. In the Shatapatha Brahmana, potent entities such as the nation, Indra, and the Sun are metaphorically portrayed as horses. The term 'Medha' is synonymous with 'Yagya'. The Nighantu texts provide 15 synonyms for Yagya, one of which is 'Medha'. In the comprehensive meaning of Ashvamedha, in Vedic rhetoric, 'Medha' signifies the awakening of intellect or wisdom. Delving into the philosophical significance of Ashvamedha in scriptural contexts is imperative to grasp this invaluable heritage. This research paper endeavors to understand Ashvamedha in the backdrop of Vedic literature, particularly by deciphering the meanings of the mantras presented in the Vedas. In Rigveda 5/27/4, Ashvamedha signifies the ultimate truth or reality; in Rigveda 5/27/5, it symbolizes the flow of creative power and the bliss represented by the essence of Soma; and in Rigveda 8/68/15 and 8/68/16, Ashvamedha is said to lead to the attainment of strength and the flow of life force. Ashvamedha leads to the enhancement of our intellect, meaning the awakening of wisdom, through which a human is established in the Supreme. The Vedas tell us that the purification of human consciousness through Ashvamedha - the awakening of wisdom - is the reward of Ashvamedha, and that the worship (Medha) of the divine power flow (Ashva) is the expansive, cosmic purpose of Ashvamedha.

Neuraminidase-3 Inhibition Improves Vascular Function in Diabetic Mice

In type 2 diabetes (T2D), endothelial dysfunction and arterial stiffening play a significant role in the development of cardiovascular disease. A central mediator of vascular dysfunction is degradation of the endothelial glycocalyx, a semipermeable mechanosensitive structure that separates the endothelium from the flow of blood and shear forces associated with it. Neuraminidase, a sialidase that cleaves sialic acid from the terminal branches of glycoproteins and glycolipids, is implicated in glycocalyx degradation. However, its role in mediating vascular dysfunction in the setting of T2D remains relatively unexplored. Herein, we tested the hypothesis that pharmacological inhibition of neuraminidase-3 (Neu3i) improves glycocalyx integrity, ameliorates endothelial dysfunction, and reduces arterial stiffness in diabetes. In support of this hypothesis, we report that, relative to vehicle-treated cells, endothelial cells exposed to Neu3i for 24hr have increased glycocalyx components including sialic acid and N-acetylglucosamine (GlcNAc), one of the amino sugars comprising the N-acetyllactosaminoglycans chains within the glycocalyx, as assessed with fluorescent lectin staining using MAA/Mal I+2 and WGA, respectively. We further show that treatment of diabetic ( i.e., db/db) mice with Neu3i for 28 days reduced aortic pulse wave velocity, with no change in blood pressure, when compared to vehicle-treated mice. Neu3i also reduced the stiffness of aortic explants, as assessed via atomic force microscopy. Excised arteries were also assessed for flow-mediated dilation and vascular stiffness using pressure myography. Diabetic mice treated with Neu3i had increased flow-mediated dilation and reduced incremental modulus of elasticity, indicative of improved endothelial function and reduced arterial stiffness. Collectively, these data support the hypothesis that Neu3 is a potential therapeutic target for the amelioration of vascular dysfunction in T2D. National Institutes of Health grant: R01HL153264 to LM-L and JP. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Thoracoscopic surgery for rare congenital pulmonary airway malformations in adults: a decade of retrospective study.

Congenital pulmonary airway malformation (CPAM) is a rare benign deformity of the lungs in adults. Our study aimed to evaluate the clinical features and compare the effect of thoracoscopic lobectomy and wedge resection for adult CPAMs. This was a retrospective study including eighteen adults with CPAMs recruited between 2013 and 2023. Radiological scans and pulmonary function test (PFT) were performed before operation. All the patients were treated with thoracoscopic approach, which were categorized into groups of lobectomy and wedge resection. The baseline, preoperative, and operative data were evaluated and analyzed. Four males and fourteen females were diagnosed with CPAMs at a median age of 57.5 years. Cough was the main symptom, reported by 55.6% of the patients. CPAMs were always initially misdiagnosed as other conditions due to heterogeneous computed tomography (CT) characteristics. The mean of PFT results showed normal (>80% predicted) in forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and FEV1 to FVC ratio (FEV1/FVC), but less than 70% predicted in forced expiratory flow (FEF) at 25-75%, 50% and 75% of FVC. All patients underwent video-assisted thoracic surgery (VATS) with a total of nine wedge resections and nine lobectomies. Age at surgery varied statistically between the two groups. Whereas, duration of surgery, blood loss, postoperative drainage, days of drainage, days of hospitalization and postoperative complications showed no statistical difference between the two groups. There were 27.8% of the lesions showing CPAMs mixed with other diseases during histological evaluations. CPAM in adults showed a complex presentation in terms of clinical symptoms, imaging performance and pathological findings. Half of the patients were detected with small airway dysfunction preoperatively. Thoracoscopic lobectomy and wedge resection for the treatment can achieve satisfactory short-term outcomes.

Forced air flow through a rectangular channel with 3D turbulence enhancers: fluid-dynamics and thermal analysis by Large Eddy Simulations

Many newer engineering applications, like the cooling of automotive batteries and high-performance CPUs, require heat exchangers (HEs) with large contact areas and very small heights. Performances of this type of HEs can be significantly improved by using surfaces enhanced with optimized 3D structures. The project Mood4hex aims at designing new geometries with optimized morphology, starting from a large database of experimental data on ribbed surfaces. In order to perform an optimization algorithm on such surfaces, analyses are carried out on CFD models with increasing complexity and computational time, to find a fast-running code that preserves the physical meaning. Until recently we used RANS models, and now we began to investigate the use of Large Eddy Simulations (LES) as a higher order validation tool for simpler models. In this paper, we present the results of LES along with experimental data of a forced air flow inside a streamwise periodic rectangular channel of high aspect ratio, i.e., 1:10, equipped with standard transverse ribs (α = 90°). More specifically, the ribs are placed only on the lower wall that is operated at constant heat flux, while air flowing at Re 500 or 1000. Comparison of experimental data vs LES results shows weaknesses and strengths of the model.

Effects of Hypopressive Abdominal Training on Ventilatory Capacity and Quality of Life: A Randomized Controlled Trial.

Pelvic floor dysfunctions, associated with alterations in respiratory mechanics and, consequently, quality of life, are the cause of the most frequent gynecological problems. Pelvic floor muscle training emerges as a first-line treatment, with new approaches such as hypopressive exercises. The aim of this study was to analyze the efficacy of an 8-week supervised training program of hypopressive exercises on the pelvic floor and its impact on improving the ventilatory mechanics and quality of life in women. Analysis of the spirometric parameters showed a significant main Group × Time effect for three parameters: the ratio of FEV1/FVC (p = 0.030), the forced expiratory flow at 75% of the expired vital capacity (p < 0.001), and the forced expiratory flow over the middle half of the forced vital capacity (p = 0.005). No statistical significance was found regarding the SF-12 questionnaire components; only differences were found over time in the physical role (p = 0.023), bodily pain (p = 0.001), and vitality (p < 0.010) domains and in the physical component summary score (p = 0.010). After an 8-week intervention of hypopressive exercises, an improvement in the ventilatory and pulmonary capacities can be observed.

Modeling and experimental analysis of CO2 methanation reaction using Ni/CeO2 monolithic catalyst

In this study, the effect of the cell density of monolithic catalysts was investigated and further mathematically modeled on cordierite supports used in CO2 methanation. Commercial cordierite monoliths with 200, 400, and 500 cpsi cell densities were coated by immersion into an ethanolic suspension of Ni/CeO2 active phase. SEM–EDS analysis confirmed that, owing to the low porosity of cordierite (surface area < 1 m2 g−1), the Ni/CeO2 diffusion into the walls was limited, especially in the case of low and intermediate cell density monoliths; thus, active phase was predominantly loaded onto the channels’ external surface. Nevertheless, despite the larger exposed surface area in the monolith with high cell density, which would allow for better distribution and accessibility of Ni/CeO2, its higher macro-pore volume resulted in some introduction of the active phase into the walls. As a result, the catalytic evaluation showed that it was more influenced by increments in volumetric flow rates. The low cell density monolith displayed diffusional control at flow rates below 500 mL min−1. In contrast, intermediate and high cell density monoliths presented this behavior up to 300 mL min−1. These findings suggest that the interaction reactants-catalyst is considerably more affected by a forced non-uniform flow when increasing the injection rate. This condition reduced the transport of reactants and products within the catalyst channels and, in turn, increased the minimum temperature required for the reaction. Moreover, a slight diminution of selectivity to CH4 was observed and ascribed to the possible formation of hot spots that activate the reverse water–gas shift reaction. Finally, a mathematical model based on fundamental momentum and mass transfer equations coupled with the kinetics of CO2 methanation was successfully derived and solved to analyze the fluid dynamics of the monolithic support. The results showed a radial profile with maximum fluid velocity located at the center of the channel. A reactive zone close to the inlet was obtained, and maximum methane production (4.5 mol m−3) throughout the monolith was attained at 350 °C. Then, linear streamlines of the chemical species were developed along the channel.

Experimental and theoretical investigations on the static behavior of low aspect ratio shear stud connectors in ultra high performance concrete

In reinforcement project for early-built orthotropic steel bridge decks (OSDs) using ultra high performance concrete (UHPC), low aspect ratio shear stud connectors in UHPC are required. In present study, push-out tests of six static UHPC specimens with and without reinforcement bars were first conducted. The failure modes, load-slip curves and shear capacity of shear stud connectors embedded in UHPC with an aspect ratio of 1.84 were investigated. Subsequently, the experimental results of shear capacity and load-slip curves were compared with the theoretical calculation results. Finally, a new theoretical model of shear stiffness was proposed for low aspect ratio shear studs based on the energy equivalence theory. The experimental results indicated that the failure mode of all specimens was stud shank failure, while the UHPC slabs without reinforcement bars showed extensive cracks. The effect of reinforcement bars on the behavior of shear studs embedded in UHPC slabs can be negligible. The reinforcement bars mainly affected the internal force flow in the UHPC, thus limiting crack initiation and extension. The compressive strength of the UHPC and the weld collar had significant impact on the shear capacity of short studs in the UHPC. In calculating the load-slip curves of short shear stud connectors in UHPC, the theoretical results calculated using the fractional form equations were in better agreement with the experimental results. The proposed theoretical model neglecting the deformation of shear stud in elastic stage can accurately predict the shear stiffness of low aspect ratio shear stud connectors in UHPC.

An instrument-free, integrated micro-platform for rapid and multiplexed detection of dairy adulteration in resource-limited environments

In dairy industry, expensive yak's milk, camel's milk, and other specialty dairy products are often adulterated with low-cost cow's milk, goat's milk and so on. Currently, the detection of specialty dairy products typically requires laboratory settings and relies on skilled operators. Therefore, there is an urgent need to develop a multi-detection technology and on-site rapid detection technique to enhance the efficiency and accuracy of the detection of specialty dairy products. In this study, we introduced a fully integrated and portable microfluidic detection platform called Sector Self-Driving Microfluidics (SDM), designed to simultaneously detect eight common species-specific components in milk. SDM integrated nucleic acid extraction, purification, loop-mediated isothermal amplification (LAMP), and lateral flow strip (LFS) detection functions into a closed microfluidic system, enabling contamination-free visual detection. The SDM platform used a constant-temperature heating plate, powered by a mobile battery, eliminated the need for additional power support. The SDM platform achieved nucleic acid enrichment and transfer through magnetic force and liquid flow driven by capillary forces, operating without external pumps. The standalone SDM platform could detect dairy components with as low as 1% content within 1 h. Validation with 35 commercially available samples demonstrated 100% specificity and accuracy compared to the gold standard real-time PCR. The SDM platform provided the dairy industry with an efficient, convenient, and accurate detection tool, enabling rapid on-site testing at production facilities or sales points. This facilitated real-time monitoring of quality issues during the production process, quickly identifying potential risks and preventing substandard products from entering the market.

A structural curve with reduced stress concentration and its elastic–plastic failure analysis

Stress concentration represents a significant concern in engineering failure analysis, influencing various failure mechanisms. Mitigating stress concentration requires the implementation of an efficient transition curve. However, traditional transition curve designs, including single-curvature, multi-curvature, elliptical, and streamlined types, prove to be suboptimal solutions. This study proposes an innovative transition curve scheme inspired by biological structures to mitigate inherent stress concentration at transition regions. Tensile tests are performed on specimens featuring various transition curve schemes to assess their mechanical performance and validate the superiority of the proposed scheme. Finite element simulation is employed to analyze stress distribution under tension and bending for the various schemes. Digital Image Correlation experiments were performed to validate the numerical simulations. Results demonstrate that the proposed scheme enhances load-bearing capacity, narrows the range of high-stress and yield regions, and optimizes force flow. By incorporating critical position and limit values of the transition curve, the proposed scheme effectively disperses stress, reducing the stress concentration factor to below 1.03. This design methodology can be applied to develop transition curves for shaft shoulders and variable section parts, thereby enhancing safety, structural stability, and durability. Ultimately, this scheme extends the lifespan of the structure.

Navigating the legal liminalities of a de facto state: Migrant precarity and placeholder identity papers in Northern Cyprus

Abstract This article studies the contested legal–political dynamics around forced migration flows to and through an unrecognized state: the Turkish Republic of Northern Cyprus (TRNC). We adopt an analytical perspective drawn from the literature on performative politics and the legal anthropology of documents to explore how migration dynamics interact with the contested legal status of the TRNC. Our two main questions are: What practical shape do the human rights of refugees and asylum seekers take in an interstitial legal space, where the foundation of law is itself subject to ambiguity, suspension, and contestation? And what implications—opportunities and hazards—does this constellation have for refugees and asylum-seekers? Drawing on interviews, lived experience and fieldwork observations, we make two arguments. First, we contend that the interstitial status of the TRNC represents both an opportunity for refugees and a threat. Secondly, we argue that a purely legal or technical understanding of legal identity and concurrent rights is inadequate; we must subject these phenomena to a politically informed analysis of the everyday practices through which legal norms and spaces are continuously shaped and reshaped.