Circular Wall Research Articles

Flow of SWCNT and MWCNT based hybrid nanofluids in a semi-circular enclosure with corrugated wall

Heat transfer mechanisms participate to fulfill the necessities of modern technologies. The phenomenon of heat transport has implementations in multiple fields including metal working, heating systems, thermal management in spacecraft, solar energy, and automobile engines. In the current novel work, heat transfer mechanism in a semi-circular enclosure with corrugated circular wall is studied numerically. A hybrid nanofluid consisting of water as the base fluid and solid particles of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) is considered. Prevailing mathematical equations are explained by finite element method with the help of COMSOL Multiphysics. The study examines various volume fractions of solid particles over a broad range. The SWCNT volume fraction is adjusted from 0.02% to 0.1%, while the MWCNT volume fraction ranged from 0.01% to 0.04%. Velocity, temperature, and pressure contours are imagined. Local and average Nusselt numbers are studied for each of the cases. The results indicate that heat transfer in the semi-circular enclosure improves with higher volume fractions of solid particles. As the volume fraction of solid particles increases, the average Nusselt number over the heated surface decreases.

In-plane impact characteristics of missing rib type anti-tri-chiral honeycomb

Previous studies have demonstrated that antichiral honeycomb materials exhibit superior mechanical properties and energy-absorbing characteristics compared to conventional hexagonal honeycomb materials. To further explore the impact resistance of antichiral honeycomb and enhance its energy-absorbing capacity, this paper introduces a novel missing rib type anti-tri-chiral honeycomb (MATCH). Derived from the original anti-tri-chiral honeycomb (ATCH), the MATCH design replaces the V-element cell wall with a circular cell wall. This paper conducts quasi-static compression experiments on 3D-printed MATCH specimens, employing a method that integrates experimental data and numerical simulation. The validity of the MATCH model is confirmed using the ABAQUS simulation software. The deformation modes of MATCH and ATCH are analyzed. Subsequently, through parametric analysis, it is observed that when φ =110° and the ligament-to-truss ratio L/r = 2, MATCH increases the plateau stress and specific energy absorption (SEA) by 162.96% and 176.09%, respectively, compared to ATCH, with a mere 7.8% relative density error. This study serves as a reference for improving energy absorption and optimizing the design of structures using future antichiral honeycomb materials.

Exponential dependence between motion acceleration and diameters of skyrmions under the driven of periodical strains

The internal strain in practical materials is usually seen as defects and a large of methods have been proposed to avoid its appearance. However, strains in magnetic materials can be effective in regulating the performance mediated by magnetoelastic coupling effect. Herein, we theoretically demonstrate the motion of skyrmions driven by time-dependent periodical strains which imitate strain fluctuations in real materials. It is found that the motion acceleration of skyrmions is exponential correlation with diameters and skyrmions can be rebounded near the end of magnetic racetrack for larger size of diameters. Such a motion results from the excitation of spin wave modes on the position of circular domain walls in skyrmions. Our results can provide insight for manipulating skyrmions by strain engineering for applications in information storage and processing.

Lateral Effects of Jet Grouting on Surrounding Soil and Circular Diaphragm Walls

The installation of high-pressure jet grout piles induces significant lateral soil displacement, which can adversely affect nearby structures, such as diaphragm walls. Based on field tests, this study systematically analyzes the lateral displacement of soil caused by two distinct grouting techniques: the intelligent sensing super jet pile (SJT) technique and the Rodin jet pile (RJP) technique. Experimental results show that the SJT technique induces less disturbance to surrounding soil, with a maximum lateral displacement of approximately 6 mm at the closest inclinometer and an influence range limited to about 4 m. A theoretical model, based on passive pile theory, was developed to predict the lateral deflection of diaphragm walls due to adjacent jet grouting. Using a finite difference algorithm, bending moments on the walls were calculated and compared to measured data, showing a consistent correlation between predictions and observations. These findings are crucial for the design and construction of jet grout piles near sensitive structures, ensuring the safety and reliability of soil improvement practices and underground engineering.

Physiochemical View of Fuel Jet Impingement and Ignition Upon Contact with a Cylindrical Hot Surface

This study delves into ignition and flame dynamics involving a cylindrical hot surface impact. Previous studies have focused on the flat-wall hot surface interacting with fuel spray, leaving gaps in understanding the effects of cylindrical hot surfaces on fuel-air mixing and ignition. Using high-fidelity large-eddy simulations (LES), this study investigates how fluid elements, upon contacting an electronically activated glow plug structure, exhibit mixing and thermochemical properties. The analysis examines how this type of structure enhances fuel-air mixing and subsequently influences the thermochemistry behavior in conjunction with the fuel-specific combustion behavior. The study includes scenarios with free spray and non-thermal deposit cases to assess their mixing impact, alongside testing five different electric voltage inputs to study the thermally assisted ignition process. Results demonstrate that the cylindrical structure hinders flow, reducing its inertia and increasing flow residence time. Moreover, a significant Coandă effect due to the circular wall structure is identified, potentially serving as a mechanism for enhancing flame-holding. Furthermore, varying the input voltage notably affects ignition timing, revealing a non-monotonic ignition delay pattern with lower voltages. Detailed analysis highlights the critical role of negative temperature coefficient (NTC)-driven low-temperature chemistry (LTC) in the ignition process.

Quantum vortex stability in draining fluid flows

Quantum vortices with more than a single circulation quantum are usually unstable and decay into clusters of smaller vortices. One way to prevent the decay is to place the vortex at the center of a convergent (draining) fluid flow, which tends to force vortices together. It is found that while the primary splitting instability is suppressed in this way (and completely quenched for strong enough flows) a secondary instability can emerge in circular trapping geometries. This behavior is related to an instability of rotating black holes when superradiantly amplified waves are confined inside a reflective cavity. The end state of the secondary instability is dramatic, manifesting as a shock wave that propagates round the circular wall and nucleates many more vortices. Published by the American Physical Society 2024

Natural convection heat transfer in an eccentric annulus filled with hybrid nanofluid under the influence of thermal radiation and heat generation/absorption

This investigation aims to scrutinize the flow and heat transfer characteristics of a hybrid nanofluid composed of Ag-MgO within an eccentric annular space, where the inner circular wall is held at a constant elevated temperature and the outer circular wall is uniformly cooled. Natural convection in such eccentric annular enclosures, with thermal radiation and the effects of heat generation/absorption taken into consideration, plays a vital role in various engineering applications, including solar collectors, nuclear reactors, thermal storage systems, and heat exchangers. The resolution of the fundamental governing equations was executed employing the Gauss-Seidel approach, with the inclusion of a sub-relaxation process, all within the framework of the finite volume method. The impact of the Rayleigh number, radiation number, volume fraction as well as heat generation/absorption coefficient on thermal transfer, flow, and temperature distributions were investigated. It was observed that for low Rayleigh numbers, radiation influences enhance flow stability and improve the conductive heat transfer mode. Conversely, at high Rayleigh numbers, radiation intensifies convective heat exchange. The growth of the Rayleigh number diminishes the impact of heat generation and reinforces the radiation heat transfer process, while heat absorption exhibits the opposite effect. From Nr = 1 onwards, the average Nusselt number values are no longer influenced by an increase in nanoparticle volumetric fraction, and they are solely linked to the radiation number.

Impact of morphological and mechanical components on inconel 625 grinding using common cylindrical grinding wheels

This study used a grinding technique based on Gas Tungsten Arc Welding (GTAW) to create walls composed of Inconel 625 alloy. Mechanical and microstructural (MM) adjustments are structural and mechanical alterations that take place during the additive manufacturing process of Inconel 625 grinding. A thorough examination of the modifications made to the nickel superalloy Inconel 625's (I-625) microstructure was conducted during the grinding process. A circular weave and a stringer bead design were used to construct the wall. Tensile properties and microstructural analyses were assessed for each wall. Using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), the fracture zones of the tensile specimens were examined. The microstructure is mostly composed of equiaxed dendrites, although a unique combination of discontinuous and continuous cellular dendrites can be observed along the cross-section. In tensile testing, circular woven walls performed better than stringer bead walls. The EDS and AFM results show that Ni and Cr make up the majority of the fracture zone, with traces of Nb and Mo. Because there are no lave phases, the fracture mode is ductile. The elemental mapping, which shows the homogenous dispersion of Ni and Cr inside the fracture zone, provides additional evidence in favor of the ductile failure mode. The UTS of the time-consuming TS samples is somewhat higher and exhibits a steadily rising bias in comparison to the specimens with quick TS. The highest level of the UTS sample is 10 %.

A novel laser interferometric method for thin film thickness measurement in gas–liquid intermittent flow

Abstract In horizontal intermittent flow, the long bubbles move toward the center of the pipe due to inertia, forming the thin liquid film above the long bubbles. Accurate measurement of the liquid film thickness is crucial for heat and mass transfer. In this paper, laser interferometric technology is innovatively introduced to measure the film thickness of the intermittent flow, and the thin liquid film is detected with a resolution of 100 nm. Considering the curvature of the circular pipe wall, which leads to divergent reflected light, the effect of the pipe wall on the interference pattern is explored by the ray tracing technique. A two-dimensional interpolation phase retrieval algorithm based on light intensity is proposed to reconstruct the thickness of the liquid film, and the average error is less than 1.86%. Benefiting from the exceptionally high resolution, research is conducted on the thin liquid film at the top of the horizontal intermittent flow, revealing its dependence on the sub-regimes and gas–liquid velocities.

Mixing Performance of a Passive Micromixer Based on Split-to-Circulate (STC) Flow Characteristics.

We propose a novel passive micromixer leveraging STC (split-to-circulate) flow characteristics and analyze its mixing performance comprehensively. Three distinct designs incorporating submerged circular walls were explored to achieve STC flow characteristics, facilitating flow along a convex surface and flow impingement on a concave surface. Across a broad Reynolds number range (0.1 to 80), the present micromixer substantially enhances mixing, with a degree of mixing (DOM) consistently exceeding 0.84. Particularly, the mixing enhancement is prominent within the low and intermediate range of Reynolds numbers (0.1<Re<20). This enhancement stems from key flow characteristics of STC: the formation of saddle points around convex walls and flow impingement on concave walls. Compared to other passive micromixers, the DOM of the present micromixer stands out as notably high over a broad range of Reynolds numbers (0.1≤Re≤80).

Asymmetric Magnon Frequency Comb.

We theoretically show the asymmetric spin wave transmission in a coupled waveguide-skyrmion structure, where the skyrmion acts as an effective nanocavity allowing the whispering gallery modes for magnons. The asymmetry originates from the chiral spin wave mode localized in the circular skyrmion wall. By inputting two-tone excitations and mixing them in the skyrmion wall, we observe a unidirectional output magnon frequency comb propagating in the waveguide with a record number of teeth (>50). This coupled waveguide-cavity structure turns out to be a universal paradigm for generating asymmetric magnon frequency combs, where the cavity can be generalized to other magnetic structures that support the whispering gallery mode of magnons. Our results advance the understanding of the nonlinear interaction between magnons and magnetic textures and open a new pathway to exploring the asymmetric spin wave transmission and to steering the magnon frequency comb.

Damage prediction and improvement method based on cutting mode of circular empty hole

Based on the theory of empty hole effect of cutting blasting, the Hopkinson effect and Saint–Venant principle are integrated to establish a two-dimensional calculation model of dynamic stress evolution of the holes wall, and then the dynamic fracture mechanism and damage distribution mode of the rock mass in the cutting area under the action of longitudinal waves are predicted. The results of the calculation and numerical simulation are verified by experiments, and the results show that: The time-varying stress function of the circular cavity wall conforms to the periodic dynamic evolution of the trigonometric function, and the theoretical calculation is consistent with the simulation results. Through the calculation of the round holes cut model and the square empty hole cut model, the change of the shape of the holes in the cut area changes the failure form of the surrounding rock mass. The circular empty hole wall is affected by the stress wave to produce "interval ring" destruction, and the effect of the reflected stretch wave is inhibited. The large range of rock mass in the square empty hole wall produces tensile and shear failure, and the rock mass collapses inward under the influence of the second stage stress. Among them, the empty space utilization rate of the square empty hole model is about 8.5 times that of the circular holes model. Vibration monitoring in the center of the cutting area shows that the vibration effect of the circular empty hole is larger than that of the square empty hole, and the proportion of rock breaking energy is lower.

Horizontal running inside circular walls of Moon settlements: a comprehensive countermeasure for low-gravity deconditioning?

Long-lasting exposure to low gravity, such as in lunar settlements planned by the ongoing Artemis Program, elicits muscle hypotrophy, bone demineralization, cardio-respiratory and neuro-control deconditioning, against which optimal countermeasures are still to be designed. Rather than training selected muscle groups only, 'whole-body' activities such as locomotion seem better candidates, but at Moon gravity both 'pendular' walking and bouncing gaits like running exhibit abnormal dynamics at faster speeds. We theoretically and experimentally show that much greater self-generated artificial gravities can be experienced on the Moon by running horizontally inside a static 4.7 m radius cylinder (motorcyclists' 'Wall of Death' of amusement parks) at speeds preventing downward skidding. To emulate lunar gravity, 83% of body weight was unloaded by pre-tensed (36 m) bungee jumping bands. Participants unprecedentedly maintained horizontal fast running (5.4-6.5 m s-1) for a few circular laps, with intense metabolism (estimated as 54-74 mlO2 kg-1 min-1) and peak forces during foot contact, inferred by motion analysis, of 2-3 Earth body weight (corresponding to terrestrial running at 3-4 m s-1), high enough to prevent bone calcium resorption. A training regime of a few laps a day promises to be a viable countermeasure for astronauts to quickly combat whole-body deconditioning, for further missions and home return.

Tactile cues compensate for unbalanced vestibular cues during progression on inclined surfaces

A previous study demonstrated that rodents on an inclined square platform traveled straight vertically or horizontally and avoided diagonal travel. Through behavior they aligned their head with the horizontal plane, acquiring similar bilateral vestibular cues – a basic requirement for spatial orientation and a salient feature of animals in motion. This behavior had previously been shown to be conspicuous in Tristram's jirds. Here, therefore jirds were challenged by testing their travel behavior on a circular arena inclined at 0°-75°. Our hypothesis was that if, as typical to rodents, the jirds would follow the curved arena wall, they would need to display a compensating mechanism to enable traveling in such a path shape, which involves a tilted frontal head axis and unbalanced bilateral vestibular cues. We found that with the increase in inclination, the jirds remained more in the lower section of the arena (geotaxis). When tested on the steep inclinations, however, their travel away from the arena wall was strictly straight up or down, in contrast to the curved paths that followed the circular arena wall. We suggest that traveling along a circular path while maintaining contact with the wall (thigmotaxis), provided tactile information that compensated for the unbalanced bilateral vestibular cues present when traveling along such curved inclined paths. In the latter case, the frontal plane of the head was in a diagonal posture in relation to gravity, a posture that was avoided when traveling away from the wall.

Emergency Strategies for Gushing Water of Borehole and Numerical Simulation on Circular Diaphragm Wall Excavation with Ring-Beams

This study explores the underground structure and soil retention capabilities of a large-scale circular diaphragm wall (93.5 m in diameter) utilized as a soil retention strategy in deep excavation projects. The symmetrical design of the wall facilitates the use of an unsupported construction method, effectively resisting soil and water pressures. Using PLAXIS 3D 2017 software, this study simulates wall deformation and ground settlement, employing three different soil models to assess behavior under standard and emergency water gushing scenarios. The results show that the hardening soil (HS) model most accurately reflects the actual deformations and settlements. This study also finds that adjusting Young’s modulus for clay significantly impacts the accuracy of soil behavior predictions, while changes in the properties of sand have minimal effects. This research highlights the challenges posed by water gushing and suggests the need for model improvements to capture better the dynamic interactions between soil and water pressure, which could lead to wall tilting. Overall, this study offers innovative and practical value, providing crucial insights for designing and mitigating strategies in large-scale circular deep excavation projects, especially in regions such as Taiwan, where such constructions are rare and face unique challenges.

Tensile behavior of TOBs bolted T-stub to circular steel tube with Reverse-Channel

The T-stub bolted to Circular Steel Tube strengthened by Reverse-Channel using Thread-fixed One-side Bolts (TOBs) under tension was studied in this paper. Through welding a reverse channel, the regular bolted flat endplate connection could be employed for the steel beam to circular steel tube column. At the same time, the reverse channel also strengthens the tube wall and extends the hole thread length. Four TOBs bolted T-stub to Circular Steel Tube strengthened by Reverse-Channel (CST-RC) specimens were designed and tested under tension. Critical parameters were determined as the outer diameter of the steel tube, the tube wall thickness, and the bolt gauge distance. Test results revealed three typical failure modes: complete yielding of the whale tube wall, thread shear failure, and complete yielding of the whole tube wall with the thread failure. As well as the tube wall thickness could effectively increase the load-bearing capacity of the connection, a larger bolt gauge distance could reduce the connection deformation. Finite Element Models (FEM) were developed to analyze the load carrying mechanism of TOBs bolted T-stubs to CST-RC. The connection deformation contour, the yield line patterns of tube wall, and the stress distribution on the threads were presented. The behavior of TOBs bolted T-stubs to CST-RC was compared to that of TOBs bolted T-stubs to Circular Steel Tube (CST), and that of TOBs bolted T-stubs to Square Steel Tube (SST). It was found that the reverse channel effectively reduces the circular tube wall deformation and increases connection load-bearing capacity.

ETHNOMATHEMATICS OF SMALL BORDER ISLANDS: LUTUR BATU ON MOA ISLAND

The people of Moa Island have a cultural heritage in the form of Lutur Batu. Lutur Batu is a construction of large stones arranged side by side to form a circular wall. Lutur Batu is used to close village boundaries and as a garden fence which aims to protect plants from wild animals. This research aims to determine ethnomathematics studies on Lutur Batu on Moa Island. The ethnomathematics study of Lutur Batu on Moa Island in this research is expected to provide a deeper understanding of the local wisdom of the people of Moa Island, as well as contribute to the recognition, maintenance, and preservation of cultural heritage with mathematical value in the region. Furthermore, an understanding of the geometric patterns and construction of Lutur Batu can be adopted in mathematics learning at school to increase students' interest in learning and understanding of mathematical concepts.This qualitative research focuses on an in-depth understanding of ways of thinking and using mathematics in the traditions and practices of making Lutur Batu in Moa Island. The results of the analysis on Lutur Batu and the manufacturing process showed that there are mathematical concepts such as circles, cylinders, comparisons, and statistics. Lutur Batu and the Mathematical concepts contained therein can be used in Mathematics learning at school to enrich learning materials, increase learning motivation and students' understanding of Mathematics concepts. Apart from that, it can increase students' insight and knowledge regarding the cultural heritage of Moa Island

Correlation Between Volume and Pressure of Intracranial Space With Craniectomy Surface Area and Brain Herniation: A Phantom-Based Study.

There are proponents of decompressive craniectomy (DC) and its various modifications who claim reasonable clinical outcomes for each of them. Clinical outcome in cases of traumatic brain injury, managed conservatively or aided by different surgical techniques, depends on multiple factors, which vary widely among patients and have complex interplay, making it difficult to compare one case with another in absolute terms. This forms the basis of the perceived necessity to have a standard model to study, compare, and strategize in this field. We designed a phantom-based model and present the findings of the study aimed at establishing a correlation of the volume of intracranial space and changes in intracranial pressure (ICP) with surface area of the craniectomy defect created during DC and brain herniation volume. A roughly hemispherical radio-opaque container was scanned on a 128-slice computed tomography scanner. Craniectomies of different sizes and shapes were marked on the walls of the phantom. Two spherical sacs of stretchable materials were subsequently placed inside the phantom, fixed to three-way connectors, filled with water, and connected with transducers. The terminals of the transducer cables were coupled with the display monitor through a signal amplifier and processor module. Parts of the wall of the phantom were removed to let portions of the sac herniate through the defect, simulating a DC. Volume measurements using AW volume share 7® software were done. Resection of a 12.7 × 11.5 cm part of the wall resulted in a 10-cm-diameter defect in the wall. Volume differential of 35 mL created a midline shift of 5 mm to the side with lesser volume. When measuring pressure in two stretchable sacs contained inside the phantom, there always remained a pressure differential ranging from 1 to 2 mm Hg in different recordings, even with sacs on both sides containing an equal volume of fluids. Creating a circular wall defect of 10 cm in diameter with an intracavitary pressure of 35 mm Hg on the ipsilateral sac and 33 mm on the contralateral sac recorded with intact walls, resulted in a true volume expansion of 48.411 cm3. The herniation resulted in a reduction of pressure in both sacs, with the pressure recorded as 25 mm in the ipsilateral sac and 24 mm in the contralateral sac. The findings closely matched those of the other model-based studies. Refinement of the materials used is likely to provide a valid platform to study cranial volume, ICP, craniectomy size, and brain prolapse volume in real time. The model will help in pre-operatively choosing the most appropriate technique between a classical DC, a hinge craniotomy, and an expansive cranioplasty technique in cases of refractory raised ICP.

Circular Section Metal Wall Cut-Off Wave guide Accurate Calculation when used as a Standard Attenuator

In this paper, the mathematical analysis is carried out from many angles, so that the theoretical calculation problem of the circular metal wall cut-off wave guide used as a premary attenuation standard is completely solved, and the Chinese national standard of the attenuation quantity is established. The benchmark was completed by the Chinese National Institute of Metrology (NIM) with an accuracy of 5×10-5; Reach the international advanced level. The calculation accuracy provided in this paper is 10-6~10-7. This is a good example of a project combining theory and practice.

Energy Performance Analysis and Study of an Office Building in an Extremely Hot and Cold Region

China is committed to reaching peak carbon by 2030 and carbon neutrality by 2060. The goals of reducing energy consumption and building a “beautiful China” are being urgently pursued in China. The building studied in this paper is located in the city of Turpan, where the problem of excessive energy use among buildings is significant due to the region’s hot summers and cold winters. Additionally, the fact that the office building studied in this paper has an east–west orientation is significant: the building’s main façade is oriented to the west, comprising a large area of single-layer glass curtain wall. Based on this, this paper proposes optimization strategies from two perspectives of renovation and new construction. Four design options are proposed at the retrofit level: glazed circular curtain wall; glazed enclosed curtain wall; west-facing double-glazed curtain wall circulation combined with south-facing light from the east; recycling of windows on the inside of the exterior glass curtain wall. These suggestions focus on retrofitting the glass curtain wall on the west elevation of the building. Two design options are proposed at the new-build level: west-facing south-oriented light and west-facing north-oriented light. These suggestions were primarily built around the idea of changing the orientation of the windows on the west elevation. The results show that the optimal solution is to implement the west-facing double-glazed curtain wall circulation combined with south-facing light from the east. This program shows a 64.14% reduction in heating energy consumption, a 77.12% reduction in cooling energy consumption, and a 69.67% reduction in total energy consumption. The above research has improved the deficiencies in the performance-based energy efficiency retrofit of office buildings in the region and provided new ideas and suggestions for policymakers and designers to build energy-efficiency retrofits in the early stages.