Constant Twist Research Articles

Understanding the Effects of Spacecraft Trajectories through Solar Coronal Mass Ejection Flux Ropes Using 3DCOREweb

This study investigates the impact of spacecraft positioning and trajectory on in situ signatures of coronal mass ejections (CMEs). Employing the 3DCORE model, a 3D flux rope model that can generate in situ profiles for any given point in space and time, we conduct forward modeling to analyze such signatures for various latitudinal and longitudinal positions, with respect to the flux rope apex, at 0.8 au. Using this approach, we explore the appearance of the resulting in situ profiles for different flux rope types, with different handedness and inclination angles, for both high- and low-twist CMEs. Our findings reveal that CMEs exhibit distinct differences in signatures between apex hits and flank encounters, with the latter displaying elongated profiles with reduced rotation. Notably, constant, nonrotating in situ signatures are only observed for flank encounters of low-twist CMEs, suggesting the existence of untwisted magnetic field lines within CME legs. Additionally, our study confirms the unambiguous appearance of different flux rope types in in situ signatures in all of the cases, barring some indistinguishable cases, contributing to the broader understanding and interpretation of observational data. Given the model assumptions, this may refute trajectory effects as the cause for mismatching flux rope types as identified in solar signatures. While acknowledging limitations inherent in our model, such as the assumption of constant twist and a nondeformable torus-like shape, we still draw relevant conclusions within the context of the global magnetic field structures of CMEs and the potential for distinguishing flux rope types based on in situ observations.

Effect of the blending between upland and combing waste on cotton fiber and yarn quality

Blending of cotton wastes with raw materials to produce different textile products has economically and environmentally beneficial. This study was carried out in Cotton Research Institute, Agricultural Research Center. This investigation aimed to study the impact of blending ratio on fiber, mechanical and physical yarn quality properties to find out the optimum blending ratio that achieves the optimum yarn quality properties. For this purpose, fiber properties, mechanical and physical yarn quality properties of ring spun yarns produced from cotton variety Giza95, Delta pine245 cotton variety (upland cotton) combed cotton waste of Extra Fine Giza93 and six different binary blend ratios were studied. Blended samples were spun into 36s, and 40s, carded yarns at constant twist multiplier 4 on ring spinning system. the results showed that fiber properties, Physical and mechanical properties of yarns produced from Giza95 were better than 100% upland cotton, 100% combed cotton waste and the other blended yarns.65% Giza95-35% combed waste of blended samples recorded higher fiber properties(maturity ratio, fiber length, uniformity index, fiber strength and fiber elongation) than all blended samples.Also,the same blended ratio at 36s, yarn count give better lea count product strength, yarn strength, yarn elongation, evenness, imperfections and yarn hairiness compared with all blended yarns followed by 65% combed waste - 35% Giza95.While, the lowest yarn quality properties recorded by The blended yarn of 35% Giza95-65% Delta pine245. Also, it observed that increasing proportion of G95 cotton variety in blended samples led to improve fiber, mechanical and physical yarn properties

Influence of W-cut twisted tape inserts on heat transfer characteristics of a counter flow heat exchanger using CeO2 nanofluid – an experimental and numerical investigations

The motive of the study is to determine the influence of W-cut twisted tape (TT) inserts on heat transfer rate (HTR) and the pressure drop of a TTCFHEx. The TT inserts involved a constant twist ratio (TR = 3) with variations in width ratio (WR) and the depth ratio (DR), respectively. Cold fluid (CeO2 nanofluid) Reynolds number (Re) varied from 2,436 to 11,626 while the hot fluid Re (Re = 8,322) is kept constant. From the study, insertion of TT insets in a TTCFHEx creates a swirl flow along with secondary vertex flow in the flow direction, leads to disruption of boundary layer thickness and which helps in improve the heat dissipation rate. Further, important findings from the study is noted that the Nusselt number (Nu) increases significantly at higher WR and DR with considerable increase in the pressure drop. However, at ϕ = 0.3% with insertion of TT inserts in a TTCFHEx, Nu number advanced by 71.52%, 80.40%, 127.65% than the base fluid without inserts. Further, at higher WR and DR the augmentation of HTR is found to be 1.5-times higher than the plain tube (PT) with considerable increase in the pressure drop. In the presence of nanofluid with W-cut TT inserts, the overall heat transfer coefficient (HTC) is enhanced by 34.68%, 41.82%, 52.65% and 36.26%, 44.25%, 50.14% for WR (4/15, 8/15, 12/15) and DR (2/15, 4/15, 6/15) compared to base fluid water with PT for both numerical and experimental investigations are considered in range of Re studied. Also, the computed experimental and numerical performance evaluation criteria (PEC) is found to be 2.16 and 2.09 for WR = 12/15 and DR = 6/15, respectively, at higher values of Re number.

FINDING THE RELATIVE TRAJECTORY OF THE CARGO IN THE BODY OF A VEHICLE WHICH IS GOING DOWN OR UP ON A CURVED SECTION OF THE ROAD

With a certain assumption, the load, which during relative movement along the bottom of the body makes translational movement, can be taken as a material point. In this case, finding the relative movement of the load in the body when the car moves along the road with a spatial axis is reduced to finding the relative trajectory of the material point. In known works, it is proposed to use the accompanying trihedron of the trajectory of the transfer motion and Frenet's formula to find the absolute acceleration vector of a point. The independent variable is not time, as in traditional problems, but the arc coordinate of the transfer trajectory, since only under this condition can Frenet's formulas be applied. The vector of absolute acceleration is obtained in projections onto the vertices of the moving accompanying trihedron, without looking for individual components (transfer, relative, and Coriolis acceleration), as is done in traditional approaches. The purpose of the study is to investigate the relative movement of the load, taken as a material point, along the bottom of the body of a truck moving along a curvilinear section of the road with a spatial axis during its ascent or descent. The spatial curve is characterized by two parameters that depend on the kinematics of the accompanying Frenet trihedron. These parameters are the curvature k and the twist σ of the curve. Their values at any point of the curve will be determined if the dependencies k=k(s) and σ=σ(s) are known, where s is the arc coordinate (the arc length of the curve). It is assumed that such a spatial curve is the axis of a curved section of the road that goes uphill or downhill. The application of the accompanying trihedron of the curve and Frenet's formulas made it possible to describe the relative motion of the cargo in the body of a car moving along a road having a spatial axis with constant and variable speeds. The regularities of the relative movement of the cargo when the car is moving on the road, the axis of which is a helical line with constant curvature and twist, have been found. It was found that there is no significant difference between the value of the relative speed of the cargo when the car moves at a constant speed down or uphill at the initial stage. When braking on a descent, a significant relative movement of the cargo is observed, which increases with an increase in the braking acceleration, and when climbing, on the contrary, the relative movement decreases with an increase in the braking acceleration. The regularity of the relative movement of the cargo when the car moves along the road with variable curvature and torsion of the axis line depends on the type of these dependencies as a function of the length of the arc of the axis line.

Atomistic insight of torsional behavior of CNT-nanocrystalline Al nanocomposites

In this study, the deformation behavior of nanocrystalline (NC) Al and carbon nanotube (CNT) reinforced NC Al nanocomposite specimens (CNT-NC Al NCs) have been inspected under torsional loading using molecular dynamics (MD) simulations. Torsional loading on the specimens has been applied using a constant twist rate (2°/ps) relative to either end of the specimen. The evolution of grain structure at the nanoscale, the changes in crystal structure at the atomic scale, and their correlation with potential energy are investigated at different stages of torsional deformation. The fracture path for NC Al and CNT-NC Al NCs is seen along the grain boundary, and the CNT fracture process in torsion is similar to tension. The (30) CNT-NC Al NC specimen has unveiled higher torsional failure strength of 69.6 % than NC Al without the CNT specimen. The interaction of the activated slip planes, stacking faults, and dislocation motion with the Burger vector have been discussed in detail during torsion deformation. The correlation between defect evolution with strain contour has also been discussed in this paper.

Heat Transfer Intensification in a Heat Exchanger by Means of Twisted Tapes in Rib and Sawtooth Forms

This experimental study aimed to intensify the aerothermal performance index (API) in a round tube heat exchanger employing twisted tapes in rib and sawtooth forms (TTRSs) as swirl/vortex flow generators. The TTRSs have a constant twist ratio of 3.0, a constant rib pitch ratio (p/e) of 1.0, and six different sawtooth angles (α = 20°, 30°, 40°, 50°, 60°, and 70°). Experiments were carried out in an open flow using air as the working fluid for Reynolds numbers between 6000 and 20,000 in the current study, which was conducted in a heated tube under conditions of uniform wall heat flux. A typical twisted tape (TT) was also tested for comparison. The experimental results suggest that TTRSs yield Nusselt numbers ranging from 1.42 to 2.10 times of those of a plain tube. TTRSs with larger sawtooth angles (α) offer superior heat transfer. The TTRSs with α = 20°, 30°, 40°, 50°, 60°, and 70° respectively, enhance average Nusselt numbers by 158%, 162%, 166%, 172%, 180%, and 187% with average friction factors of 3.51, 3.55, 3.60, 3.67, 3.75 and 3.82 times higher than a plain tube. Additionally, TTRSs with sawtooth angles (α) of 20°, 30°, 40°, 50°, 60°, and 70° offer APIs in the ranges of 0.99 to 1.19, 1.01 to 1.21, 1.03 to 1.26, 1.05 to 1.31, 1.07 to 1.42, and 1.09 to 1.48, respectively, which are higher than those of the typical twisted tape (TT) by around 5%, 7%, 11%, 16%, 25%, and 31%, respectively. This demonstrates that twisted tapes in rib and sawtooth form (TTRSs), with appropriate geometries, give a promising trade-off between enhanced heat transfer and an increased friction loss penalty.

Twisted multilayer nodal superconductors

Twisted bilayers of nodal superconductors were recently proposed as a promising platform to host superconducting phases that spontaneously break time-reversal symmetry. Here we extend this analysis to twisted multilayers, focusing on two high-symmetry stackings with alternating ($\pm \theta$) and constant ($\theta$) twist angles. In analogy to alternating-twist multilayer graphene, the former can be mapped to twisted bilayers with renormalized interlayer couplings, along with a remnant gapless monolayer when the number of layers $L$ is odd. In contrast, the latter exhibits physics beyond twisted bilayers, including the occurrence of `magic angles' characterized by cubic band crossings when $L \mod 4 = 3$. Owing to their power-law divergent density of states, such multilayers are highly susceptible to secondary instabilities. Within a BCS mean-field theory, defined in the continuum and on a lattice, we find that both stackings host chiral topological superconductivity in extended regions of their phase diagrams.

Numerical simulations of the nonsymmetric growth and remodeling of arteries under axial twisting

Blood vessels are often subjected to axial twisting during body movement or surgery. Sustained twisting may lead to blood vessel growth and remodeling, however, it remains unclear how the extracellular matrix in the blood vessels remodel under sustained axial twisting. This study aimed to develop a computational model to simulate stress-induced growth and remodeling (G&R) of thin-walled blood vessels under axial twisting. Cylindrical vessels were subjected to a step increase in axial torque while the axial stretch and lumen pressure remained constant. The vessel walls were modeled based on the constrained mixture theory given as microstructure-based discrete fiber families with isotropic matrix structure models. Simulation results demonstrated that in response to a constant twist angle loading, arterial wall thickness, mass, and twisting torque gradually increase towards a new steady state. However, the stress and mass decrease in one diagonal fiber family while increasing in the other diagonal fiber family before reaching plateaus. A novel finding was that the two helical collagen fiber families showed different growth rates and patterns during remodeling, driven by the different fiber stresses generated by the twisting, and led to non-symmetric material properties. This study sheds new light on arterial wall remodeling under axial twisting.

Investigation on two-phase fluid mixture flow, heat transfer and entropy generation of a non-Newtonian water-CMC/CuO nanofluid inside a twisted tube with variable twist pitch: Numerical and evolutionary machine learning simulation

A 3-D numerical investigation is performed to evaluate the effect of variable twist pitch on the hydrothermal behavior and entropy generation features of non-Newtonian water-CMC/CuO nanofluid (NF) flow inside a twisted tube with a square cross-section. Three twisted tubes with a length of 500 mm, each of which has 3 twists, are considered. The first tube (Case I) has a constant twist pitch of 100 mm, while the twist pitch of Case II (150.0, 127.5, 100.8, 74.2, and 47.5 mm) and Case III (190, 144.6, 97.9, 51.3, and 6.2 mm) are variable. The simulations are performed using the two-phase mixture method considering different nanoparticle concentrations (ϕs) of 0–3% and Reynolds numbers (Res) of 600–1500. Based on the results, the highest and lowest overall hydrothermal performance was obtained for Case II and Case I, respectively. Moreover, the lowest ratios of thermal and frictional entropies of NF flow in the twisted tube to those of the plain tube were obtained for Case II. As another novelty of the current work, an evolutionary machine learning approach, namely, gene expression programming (GEP), was adopted to simulate the first law and second law performances of the NF in Case III.

Twisted kink dynamics in multiflavor chiral Gross–Neveu model

The Gross–Neveu model with UL(N f) × UR(N f) chiral symmetry is reconsidered in the large N c limit. The known analytical solution for the time dependent interaction of any number of twisted kinks and breathers is cast into a more revealing form. The (x, t)-dependent factors are isolated from constant coefficients and twist matrices. These latter generalize the twist phases of the single flavor model. The crucial tool is an identity for the inverse of a sum of two square matrices, derived from the known formula for the determinant of such a sum.

Resonant interaction in chiral Eshelby-twisted van der Waals atomic layers

We study the electronic structures of chiral, Eshelby-twisted van der Waals atomic layers with a particular focus on a chiral twisted graphite (CTG), a graphene stack with a constant twist angle $\theta$ between successive layers. We show that each CTG can host infinitely many resonant states which arise from the interaction between the degenerate monolayer states of the constituent layers. Each resonant state has a screw rotational symmetry, and may have a smaller reduced Brillouin zone than other non-resonant states in the same structure. And each CTG can have the resonant states with up to four different screw symmetries. We derive the energies and wave functions of the resonant states in a universal form of a one-dimensional chain regardless of $\theta$, and show that these states exhibit a clear optical selection rule for circularly polarized light. Finally, we discuss the uniqueness and existence of the exact center of the lattice and the self-similarity of the wave amplitudes of the resonant states.

Thermo-hydraulic Performance Investigation of Twisted Tapes Having Teardrop-Shaped Dimple-Protrusion Patterns

The teardrop pattern observed to be more efficient in straight tubes was examined for the first time in a twisted tape wall. The thermo-hydraulic performances of twisted tapes having periodically teardrop-shaped dimple-protrusion patterned walls are numerically investigated. The new designs have two different densities (N=30, and 45), three alternative types of layouts (composed of only protrusions, only dimples, and a combination of dimples and protrusions) align in two different flow directions. Designs have a constant twist ratio (TR) of 3, and calculations are conducted for Reynolds numbers (Re) between 3000 and 27000 by Ansys Fluent under a constant heat flux of 50000 W/m2. All cases have higher Nusselt number (Nu) values than traditional twisted tape (TT) in the tested Re region. Besides, all arrangements except the teardrop protruded twisted tape have higher thermal performance factors than the TT in the Re range from 3000 to 5500. All dense versions of the teardrop patterned twisted tapes have higher Nu and friction factor (f) than sparse versions of them. The dense teardrop dimpled-protruded (D-TDP) case reaches TPF of 1.517, the highest value among the tested twisted tapes, at Re = 3000.

Heat transfer augmentation using periodically spherical dimple-protrusion patterned walls of twisted tape

The heat transfer performances of pipes with twisted tape inserts having periodically spherical dimple-protrusion patterned walls are numerically investigated by Ansys Fluent under a constant heat flux of 5 W/cm2. The inserts having three different densities (N = 0, 30, and 45) and three different kinds of arrangement (composed of only dimples, only protrusions, and a combination of dimples and protrusions) with a constant twist ratio of 3 were tested for Reynolds numbers (Re) within the range from 3000 to 27000. Comparing the turbulence models proposed the validated realizable k-ϵ model coupled with enhanced wall function to employ on the numerical simulations. While the highest Nusselt number (Nu) and friction factor (f) values for the presented study were found for the dense protruded twisted tape (D-PT) arrangement at Re values lower than 18000 and for dense dimpled-protruded twisted tape (D-DPT) arrangement for the Re greater than 18000, dimpled-protruded twisted tape (DPT) and dimpled twisted tape (DT) sequences reached the lowest f values of 0.365 and 0.322 at Re = 3000, respectively. D-DPT and D-PT sequences reached the highest thermal performance factor (TPF) values of 1.508 and 1.478 at Re = 3000, respectively. All patterned twisted tapes performed better Nu than conventional twisted tapes in the analyzing range and performed better TPF than typically twisted tapes in the Re region of less than 6000.

A Study of The Plied Yarn Twist Factor.(Dept.T)

This paper presents a new formula of twist multiplier for plied yarns. The study concerned the influence of several parameters such as: Fiber parameters, the bottom twist, single yarn liear density of plies. The experiments carried out on Ring-Spun plied cotton yarns and theoretical analysis based on the idealized yarn structure. The results obtained with predicted formula show a constant twist multiplier for all plied yarns.

Constant twist rate response of symmetric and asymmetric Σ5 aluminium tilt grain boundaries: molecular dynamics study of deformation processes

Room temperature torsional deformation behaviour of bicrystal aluminium specimens (corresponding to Σ5 family) is studied by the application of constant twist rate using molecular dynamics simulations by employing the (embedded atom method) EAM potential. To simulate the torsional loading, periodic boundary condition is employed in x-direction, whereas shrink-wrapped boundary condition is applied in y- and z-directions. A constant twist rate of 1°/ps has been applied at either end of the samples in opposite directions. The variation of potential energy as a function of relative rotation between the ends of the specimen is recorded. The evolution of different types of dislocation and characteristics behaviour due to interactions among dislocations during deformation has been analysed. The populations of Shockley partial dislocations, dislocation loops, dislocation locks, and dislocation junctions increase as the torsional deformation progresses. The structural variations occurred in the specimen are explained with the aid of defect evolutions (such as vacancies population and amorphous atoms percentage as a function of torsion angle), and the grain boundary migration and grain rotation processes are described with atomic snapshots. Additionally, we have tried to correlate trends between grain boundary energy and various deformation mechanisms.

Characterization and quantification of railroad spiral-joint discontinuities

In this study, a new approach is proposed for the characterization and quantification of the spiral transitions in railroad vehicle system algorithms. Definitions of the super-elevation and balance speed are provided in order to have a better understanding of their variations within the space curve of the spiral segment. In order to develop this understanding, three different curves which have fundamentally different geometries are considered; a super-elevated constant-curvature curve with zero twist and zero vertical elevation, a vertically-elevated helix curve with a constant curvature and twist and zero super-elevation, and a spiral curve with non-zero varying-curvature, twist, super-elevation, and vertical elevation. The curve equations are developed in terms of Euler angles used by the rail industry to describe the track geometry in the computer simulations. Because the geometry of the spiral space curve can be completely defined in terms of two Euler angles only, the horizontal-curvature and the vertical-development angles; a third Euler angle referred to as the Frenet bank angle is written in terms of these two angles using an algebraic equation. The fact that, for given curvature and elevation angles, the Frenet bank angle cannot be treated as an independent geometric parameter is used to obtain accurate quantification of the spiral-intersection discontinuities. The severity of the twist and elevation discontinuities at the spiral intersections with the tangent and curve segments demonstrates the need for the adjustments used in practice by the rail engineers to achieve a higher degree of smoothness. In order to properly define the direction of the centrifugal force, a distinction is made between the super-elevation of a surface and the bank angle of a curve on the surface.

New Expression for Evaluating the Mean Crosstalk Power in Weakly-Coupled Multi-Core Fibers

A closed-form expression is proposed for evaluating the mean inter-core crosstalk (ICXT) power in weakly-coupled multi-core fibers (WC-MCFs), with cores’ propagation constants perturbed by bending, twist, and random structure fluctuations. This expression generalizes the expression proposed by Koshiba et al. by taking the dependence of the propagation constants on the longitudinal coordinate of the fiber (induced by constant bending and twist along the MCF) into account in a more rigorous way. We provide a physical interpretation of the proposed expression as the convolution of the spectrum of the $z$ -dependent component of the propagation constant induced by the bending and the spectrum of the perturbation induced by the structure fluctuation. The accuracy of the proposed closed-form expression is assessed by comparing simulation results of the coupled-mode equations with the theoretical predictions from the proposed expression. Very good agreement of the mean ICXT power estimates is shown in the whole range of tested bending radius, difference of intrinsic effective refractive indexes of cores, twisting period and correlation length, for fiber lengths longer than one half of the twisting period and five times the correlation length. We show that the proposed expression enables evaluating the mean ICXT power in WC-MCFs with improved accuracy relative to Koshiba's expression: remarkable differences of mean ICXT power, that may exceed $\text{6}\;\text{d}\text{B}$ , can occur between the estimates provided by the Koshiba's expression and the closed-form expression derived in this article, particularly for high correlation length and twisting rate. Differently from the expression proposed by Koshiba et al. , the proposed closed-form expression predicts that the twisting period may have a significant influence on the mean ICXT power, in qualitative agreement with experimental results reported by other authors.

Electronic Constant Twist Angle Control System Suitable for Torsional Vibration Tuning of Propulsion Systems

Currently, great emphasis on reducing energy consumption and harmful emissions of internal combustion engines is placed. Current control technology allows us to customize the operating mode according to the currently required output parameters, while the tuning of mechanical systems in terms of torsional vibration is often ignored. This article deals with a semi-active torsional vibroisolation system using pneumatic flexible shaft coupling with constant twist angle control. This system is suitable, as it is specially designed, for the tuning of mechanical systems where the load torque has fan characteristics (fans, ship propellers, pumps). The main goal of this research is to verify the ability of an electronic control system developed by us to maintain the pre-set constant twist angle of the used pneumatic flexible shaft coupling during operation. The constant twist angle control function was tested on a laboratory torsional oscillating mechanical system. Presented results show that the proposed electronic control system meets the requirements for its function, namely that it can achieve, sufficiently accurately and quickly, the desired constant twist angle of the pneumatic flexible shaft coupling. It is possible to assume that the presented system will increase the technical level of the equipment where it will be applied.

Three-dimensional topological twistronics

We introduce a theoretical framework for the new concept of three-dimensional (3D) twistronics by developing a generalized Bloch band theory for 3D layered systems with a constant twist angle $\theta$ between successive layers. Our theory employs a nonsymmorphic symmetry that enables a precise definition of an effective out-of-plane crystal momentum, and also captures the in-plane moir\'e pattern formed between neighboring twisted layers. To demonstrate the novel topological physics that can be achieved through 3D twistronics, we present two examples. In the first example of chiral twisted graphite, Weyl nodes arise because of inversion-symmetry breaking, with $\theta$-tuned transitions between type-I and type-II Weyl fermions, as well as magic angles at which the in-plane velocity vanishes. In the second example of twisted Weyl semimetal, the twist in the lattice structure induces a chiral gauge field $\boldsymbol{\mathcal{A}}$ that has a vortex-antivortex lattice configuration. Line modes bound to the vortex cores of the $\boldsymbol{\mathcal{A}}$ field give rise to 3D Weyl physics in the moir\'e scale. We also discuss possible experimental realizations of 3D twistronics.

The retardation effect of static torsion on fatigue crack growth in strip steel

AbstractThis study is aimed at analysing the effect of static torsion on Mode I fatigue crack growth behaviour. Experiments have been conducted under constant torque or constant twist angle with different load ratios on SAPH440 and DP780 strip steels. The experimental results showed that the application of the static torsion or twist angle extended the fatigue life of the specimens in all cases. The fatigue life showed a positive relationship with the applied torque or twist angle until some critical value. No additional improvement in fatigue life was found after the critical value. The mechanism of the retardation due to static torsion was discussed and supported by the microscope fractography analysis. An effective stress intensity factor expression was proposed based on the fractography analysis to estimate the fatigue crack growth under constant torque in the low torque condition. The parameters introduced in the expression were found to have relationships with the dimensionless quantity related to torque, tensile load, and specimen geometry. The proposed expression achieved reliable estimates of the SAPH440 and DP780 constant torque experimental results.