Variable Tension Research Articles

Addendum: Variable brane tension and dark energy

Abstract This article is an addendum to [2024 EPL 145 39001]. In the original article, we discussed how a variable brane tension could explain the late time cosmic acceleration of the universe. In this article, we extend the results to include early-time cosmic acceleration, i.e., inflation. Thus, this work unifies the early and late-time cosmic acceleration within a single framework. We also discuss how this proposal can aid in the formation of Primordial Black Holes (PBHs).

Numerical simulation of fabric cold pad-batch winding and quality assessment of fabric in roll

Proper fabric winding quality is crucial for achieving desired finishing effects in cold pad-batch dyeing. In this work, a detailed 3D finite element model and assessment criteria were established to analyze the influences of winding pattern, pick-up, and tension function on fabric winding quality, revealed the complex relationship between winding process and fabric roll shape. Material viscoelasticity’s time-dependent effects on stress distribution were considered. Results show that employing a following roller effectively suppresses tangential creases and axial streaks but increases seam imprints and reduces fabric roundness. Increasing pick-up improves winding quality by reducing creases, streaks, and compression deformations. However, it also elevates internal radial stress, hindering control over seam imprints. Winding with variable tension, conicity coefficient α and power index i have significant impacts on coiling quality. In addition, increasing α or decreasing i effectively enhances winding quality, with the power function performing better in tension adjustment and overall winding quality.

Existence and asymptotic behavior of a nonlinear axially moving string with variable tension and subject to disturbances

In this paper, we consider the stabilization question for a nonlinear model of an axially moving string. The model is assumed to undergo the variable tension and variable disturbances. The Hamilton principle is used to describe the dynamic of transverse vibrations. We establish the well-posedness by means of the Faedo-Galerkin method. A boundary control with a time-varying delay is designed to stabilize uniformly the string. Then, we derive a decay rate of the solution assuming that the retarded term be dominated by the damping one. Some examples are given to clarify when the rate is exponential or polynomial.

DNS of Marangoni effects on a suspension of droplets in microgravity using the unstructured conservative level-set method

The multi-marker unstructured conservative level-set (UCLS) method for two-phase flow with variable surface tension is used for the Direct Numerical Simulation of thermocapillary-driven motion of a bi-dispersed suspension of droplets in microgravity. The so-called Marangoni stresses induced by surface tension gradients on the interface lead to a coupling of the momentum transport equation and the thermal energy transport equation. The finite-volume method discretizes the transport equations on three-dimensional collocated unstructured meshes. The UCLS method performs interface capturing with mass conservation of the fluid phases, whereas the multiple marker approach circumvents the numerical coalescence of fluid particles. The fractional-step projection method solves the pressure-velocity coupling. Unstructured flux-limiters schemes discretize the convective term in transport equations. Numerical and physical findings are reported.

Numerical analysis of thermophoretic particle deposition in a magneto-Marangoni convective dusty tangent hyperbolic nanofluid flow – Thermal and magnetic features

Abstract In the current study, we focus on the Magneto-Marangoni convective flow of dusty tangent hyperbolic nanofluid (TiO2 – kerosene oil) over a sheet in the presence of thermophoresis particles deposition and gyrotactic microorganisms. Along with activation energy, heat source, variable viscosity, and thermal conductivity, the Dufour-Soret effects are taken into consideration. Variable surface tension gradients are used to identify Marangoni convection. Melting of drying wafers, coating flow technology, wielding, crystals, soap film stabilization, and microfluidics all depend on Marangoni driven flow. This study’s major objective is to ascertain the thermal mobility of nanoparticles in a fluid with a kerosene oil base. To improve mass transfer phenomena, we inserted microorganisms into the base fluid. By using similarity transformations, the resulting system of nonlinear partial differential equations is converted into nonlinear ordinary differential equations. Using a shooting technique based on RKF-45th order, the numerical answers are obtained. For various values of the physical parameters, the local density of motile microorganisms, Nusselt number, skin friction, and Sherwood number are calculated. The findings demonstrated that as the Marangoni convection parameter is raised, the velocity profiles of the dust and fluid phases increase, but the microorganisms, concentration, and temperature profiles degrade in both phases.

Variable brane tension and dark energy

In this letter, we show that in a particular braneworld scenario with variable brane tension, we obtain matter acting as dark energy while the gravitational constant G promoted to a scalar field on the brane plays the role of matter (both in the sense that they have an “effective” equation of state equivalent to that of dark energy and matter, respectively). This result is interpreted from the Friedmann equation obtained from our model that exactly matches the standard Friedmann equation of general relativity with a cosmological constant Λ in terms of the aforementioned quantities. The universe is assumed to consist of only matter and dark energy in this model which is a good approximation for our universe.

Synchronize your chrono-brane: testing a variable brane tension model with strong gravitational lensing

Brane world models have shown to be promising to understand the late cosmic acceleration, in particular because such acceleration can be naturally derived, mimicking the dark energy behaviour just with a five dimensional geometry. In this paper we present a strong lensing joint analysis using a compilation of early-type galaxies acting as a lenses, united with the power of the well studied strong lensing galaxy cluster Abell 1689. We use the strong lensing constraints to investigate a brane model with variable brane tension as a function of the redshift. In our joint analysis we found a value n=7.8-0.5+0.9\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$n = 7.8^{+0.9}_{-0.5}$$\\end{document}, for the exponent related to the brane tension, showing that n deviates from a Cosmological Constant (CC) scenario (n=6). We obtain a value for the deceleration parameter, q(z) today, q(0)=-1.2-0.8+0.6\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$q(0)=-1.2^{+0.6}_{-0.8}$$\\end{document}, and a transition redshift, zt=0.60±0.06\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$z_t=0.60\\pm 0.06$$\\end{document} (when the Universe change from an decelerated phase to an accelerated one). These results are in contrast with previous work that favors CC scenario, nevertheless our lensing analysis is in agreement with a formerly reported conclusion suggesting that the variable brane tension model is able to source a late cosmic acceleration without an extra fluid as in the standard one.

Development of methodological solutions for the efficient development of gas condensate deposits in low-permeability reservoirs with complex phase behavior of reservoir fluid

Efficient production of gas and condensate from deep deposits requires the solution of a set of scientific and methodological problems, including the assessment of distribution of the initial fluid composition and properties within the deposit; predicting the complex phase behavior of the reservoir fluid at near-critical conditions and under the influence of the porous medium; modeling the formation of condensate banks in multiphase flows, taking into account velocity effects, variable interfacial tension, non-equilibrium phase transitions and complex well completions; etc. The paper presents the developments of Oil and Gas Research Institute of the Russian Academy of Sciences in this area, with an emphasis on recovery of the unique hydrocarbon reserves of the Achimov deposits of the Urengoy oil and gas condensate field.

Hydrodynamics and Heat Transfer of Cavitation Bubble in Nanoparticles/Water Nanofluids Based on the Effects of Variable Surface Tension and Viscous Forces

This paper aims to investigate the unsteady oscillatory flow of water-based nanofluids MoS2 and SiO2 past a parallel plate channel filled with a saturated porous medium. The basic equations are solved analytically using the perturbation technique subject to the appropriate boundary conditions. A numerical evaluation of the analytical results is performed, and the effects of various physical parameters on velocity, temperature, and concentration profiles within the boundary layer are analyzed. Molybdenum disulfide MoS2 nanoparticles are well known for their low friction coefficient, good catalytic activity, and excellent physical properties. At the same time, Silicon dioxide (SiO2) nanoparticles are treated to have a porous structure, very high surface activity, and adsorption properties, which makes them suitable for developing high-capacity antimicrobial agents. Hence these nanoparticles can be considered for Nanoscale elements’ performance to make rigorous thermal quality nano liquids. Thus from engineering curiosity, the skin friction coefficient, Nusselt number, and Sherwood numbers are evaluated for significant parameters at cold and heated walls by utilizing MoS2 and SiO2 nanoparticles. It would give rise to novel features that can revolutionize biology, medicine, catalysis, and other smart fields. Furthermore, graphs and tables are used to describe a comparative study of the water-based nanofluids MoS2 and SiO2. It is found that when the radiation parameter Ra is increased by 200%, the average heat transfer rate at the heated channel wall containing MoS2 and SiO2 nanoparticles in the base fluid is decreased by 6.9% and 8.3%, respectively. Further, it is found that SiO2-water nanofluid has more effectiveness towards heat transfer compared to MoS2-water nanofluid.

Free Surface Motion of a Liquid Pool with Isothermal Sidewalls as a Benchmark for Marangoni Convection Problems

In single phase flows, benchmarks like the lid driven cavity have become recognized as fundamental tests for newly developed computational fluid dynamics, CFD, codes. For multiphase free surface flows with variable surface tension, the presently studied pool with isothermal sidewalls is suggested as it is the simplest domain where Marangoni effects can dominate. It was also chosen due to its strange sensitivity to the initial setup which is discussed at length from a chosen number of ‘scenarios’. It was found that the fluid interface can reverse deformation by a change in the top boundary condition, the liquid equation of state, and the gravity level. For the top boundary condition, this reversal is due to vapor expansion within the closed volume, creating an additional convection mechanism. Not only does the interface reverse, but the peak height changes by more than an order of magnitude at the same Marangoni number. When including gravity, the peak velocity can increase significantly, but it can also cause a decrease when done in combination with a change in the top wall boundary condition. Finally, thermal expansion of the liquid phase causes the peak velocity to be reduced, with additional reductions from the gravity and top wall condition. The differences in each scenario could lead to significant errors in analyzing a practical application of Marangoni flows. Therefore, it is important to demonstrate that a new CFD code can not only resolve Marangoni convection, but also has the capability to resolve the scenario most relevant to the application at hand.

Pseudopotential Lattice Boltzmann Model for Immiscible Multicomponent Flows in Microchannels

To investigate droplet formation in a microchannel with different walls, simulations were conducted based on a pseudopotential model using the exact difference method force scheme. The variable surface tension was obtained using Laplace’s law, and the static contact angle was estimated using a first-order linear equation of the corresponding control parameter of the model. The droplet motion in microchannels was simulated using our model, and the effects of surface wettability and the Bond number on the droplet motion were investigated. The droplet motion for the intermediate microchannel wall took a significantly shorter time than that for the hydrophilic wall, and the wet length also depended on the contact angle. As the Bond number increased, the wet length of the droplet decreased on the hydrophilic surface. The droplet formation in a T-junction device was also simulated using the proposed model, and the effects of the capillary number and viscosity ratio on droplet formation were discussed in detail, and some empirical correlations between the capillary number and dimensionless droplet length are presented according to different viscosity ratios. The three flow patterns of droplet formation were categorized by the different capillary numbers as the dripping–squeezing, jetting–shearing, and threading regimes. In the dripping–squeezing regime, the droplet volume was nearly independent of the viscosity ratio, but the viscous effect was more prone to occur in the jetting–shearing regime. In the jetting–shearing regime, as the capillary number increased, the effect of the viscosity ratio on droplet formation became more significant.

Nonlinear Analysis of a Viscoelastic Beam Moving with Variable Axial Tension and Time-Dependent Speed

Nonlinear Analysis of a Viscoelastic Beam Moving with Variable Axial Tension and Time-Dependent Speed

Second-order accurate implicit finite volume method for two-dimensional modeling of PFAS transport in unsaturated porous media with variable surface tension

Per- and polyfluoroalkyl substances (PFASs) have become emerging contaminants of critical concern. Comprehensive understanding of the transport and fate of PFAS in the vadose-zone, a type of water-unsaturated porous media, is key to determination of the risks of the PFAS contamination in the subsurface and to the development of the effective remediation strategies. Accurate modeling of the PFAS transport in the unsaturated porous media is still a challenge due to the variable surface tension induced by the adsorption of PFAS to the air-water interfaces. In an effort to address this challenge, we propose a multidimensional modeling framework for the transient PFAS transport in the unsaturated porous media based on the second order accuracy finite volume method. In the modeling, the adsorption of PFAS to the solid surfaces and to the air-water interfaces is described by the two-domain sorption kinetics model, i.e., both the instantaneous and the rate limited PFAS adsorptions are taken into account. The diffusive and convective terms in the governing equations for the PFAS transport and the water flow are discretized by the central difference and the quadratic upstream interpolation for convective kinetics schemes, respectively. We investigate the effects of the convergent criteria, coupling method, and variation of the surface tension on the average and the local PFAS concentration and water content in the computational domain. We find that the convergent criteria should be chosen carefully so as to get the accurate results. The differences between the different coupling methods are affected by the boundary conditions. The variation in the surface tension due to the variation of the PFAS concentration cannot be neglected. The dimensionless parameters relevant to the properties of porous media as well as the relation between the surface tension and the PFAS concentration play an important role in transport of PFAS in the unsaturated porous media. The effects of the Péclet number, Damköhler values, and fraction of instantaneous sorption are not significant in the ranges studied in this work. These findings provide a better understanding of transport of PFAS in the vadose zone.

Quantificational 4D visualization and mechanism analysis of inhomogeneous electrolyte wetting

The inhomogeneous electrolyte distribution in lithium-ion batteries affects lithium-ion transfer, which attenuates battery performance and leads to thermal runaway. Moreover, real-time quantitative observations and an in-depth understanding of electrolyte wetting remain limited because of the harsh electrochemical environment. In this study, in-situ 4D X-ray computed tomography was used to monitor the electrolyte wetting by adding a contrast agent to the electrolyte. The mechanism through which the winding stress influenced electrolyte wetting was elucidated using a combination of experimental and porous-media-flow simulation methods. The winding stress was found to affect the soaking time and uniformity of the electrolyte distribution. Optimization strategies involving variable tension and pressurized injection improved the uniformity of the electrolyte wetting and shortened the electrolyte wetting time. This study provides practical guidance for the optimization of the electrolyte filling during battery fabrication.

Nonlinear vortex-induced vibrations of fluid-conveying tensioned pipes in super-critical regimes

Nonlinear vortex-induced vibration (VIV) properties of the fluid-conveying pipes in super-critical regimes subjected to the combined action of external fluid and axial tension are investigated. A new nonlinear dynamic model taking into account the variation of axial tension and the action of external flow is proposed. According to the van der Pol equation, the interaction between the pipe and external flow is evaluated. More specifically, the nonlinear governing equations are established based on Hamilton's principle, and they are then discretized via the Galerkin method and solved by the fourth-order Runge-Kutta method. The VIV amplitudes obtained from the present theoretical model are compared with the published experimental results, which validates the effectiveness and accuracy of the proposed nonlinear dynamic model. It is found that keeping the external fluid velocity constant, with the increase of internal fluid velocity, the growth rates of the maximum response amplitudes in different directions of the buckled pipe are the same under different tensions. When the internal fluid velocity is kept constant, for the pipe in post-buckling state, increasing the tension will be accompanied by decreasing the dynamic stiffness of the pipe, which leads to the increase of the dynamic displacement response. When the pipe in super-critical regime is subjected to variable tension, the increase of the time-varying tension amplitude can either enhance the maximum response amplitude in the cross-flow (CF) direction of the pipe or suppress it.

Analysis of natural frequency of deep-sea mining beam riser considering mixing pump

In this study, the Euler–Bernoulli beam was used to calculate the mining riser under variable tension by considering the riser as a beam vibration problem. The natural frequency and mode shape of the mining riser are investigated based on the Wentzel–Kramers–Brillouin (WKB) method. The influence of different mixing pump masses and positions is calculated using a continuous function. The bottom boundary condition of the mining riser is also considered in the calculation. The calculation results show that when the hinged boundary condition at both ends changes to a horizontal-free condition at the bottom, the natural frequencies decrease. When considering the effect of the mixing pump, note that the larger the mass of the mixing pump, the greater the increase in the natural frequency of the riser. The magnitude of increase becomes more evident as the mode grows. Furthermore, the closer the position of the mixing pump to the bottom, the higher the natural frequency. The eigenfunction is also deflected at the mixing pump position.

Fiber Tensioning Systems in a Robotized Winding Procedure for Composite Materials Building Processes

The winding process of carbon fiber is not a new concept, but until now only a few studies have been made in carbon fiber tensioning and winding on complex shapes. The main purpose of the article is to analyze the possibility to conduct the carbon fiber winding using two industrial robots connected as master slave, one to realize the winding and the other to hold and rotate the mandrel, using an own design of an automatic fiber tensioning tool. To have control of the system a force transducer was implemented. The measured force was used to make trajectory adjustments for the robots, having a predefined trajectory. The results obtained from the experimental tests showed that the winding process with two robots and a tensioning system can realize fiber windings with variable tension in molds with complex configurations (3D) of the winding paths. In this way, compact structures of the constantly tensioned fiber bundle can be obtained, according to product requirements.

Magnetic Fractionation of Red Blood Cells Based on Oxygen Saturation in Sickle Cell Disease

Anemias are a broad classification of red blood cell (RBC) disorders which effectively result in inadequate oxygen transport in the body. Sickle Cell Disease (SCD) results from a point mutation in hemoglobin, and the hemoglobin-oxygen equilibrium becomes right shifted (i.e., SCD RBCs do not oxygen saturate to the same degree as healthy RBCs). RBC exchange transfusion is a common clinical practice to increase the oxygen carrying capacity of a SCD patient - a process by which the patient's own RBCs are exchanged with healthy donor blood. During this process, large amounts of donor RBCs are discarded along with the patients SCD RBCs. Here we present a new RBC separation modality based on hemoglobin-oxygen equilibrium.It is well known that RBCs become magnetized as a function of the oxygen saturation of its hemoglobin. Due to the difference in hemoglobin-oxygen equilibrium for healthy and SCD RBCs we demonstrate a magnetic method of fractionating RBCs based on oxygen saturation. In our study, we use the SCD transfusion waste product and sort this sample into healthy fractions and SCD fractions using a field flow permeant magnetic separator. Under variable oxygen tension of the sample, we preformed the magnetic sorting.By incorporation of magnetic separation into RBC exchange processes, more efficient selection, and removal of SCD RBCs can be accomplished. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Sensing performance of engineered cementitious composites in different application forms

The method of application of self-sensing composites in structural health monitoring is urgent to be determined before real application. In this paper, the mechanical and sensing properties of self-sensing engineered cementitious composites (ECC) under monotonic and variable amplitude cyclic tension and compression were analyzed. With the consideration of different application forms such as sensor, coating and bulk types, three kinds of concrete samples were prepared. For each sample, the sensing properties and applicability of piezoresistive effect were analyzed and compared. The results demonstrate that the developed self-sensing ECC guarantees desirable sensing performances and high ductility with a tensile strain of above 6.0%. The gauge factor (GF), signal-to-noise ratio (SNR) and repeatability are 165.48, 53.07 and 4.19%, respectively in compression, while they are 14.71, 25.05 and 7.16%, respectively in tension. It was verified that the sample strain could be constantly monitored by self-sensing ECC, especially when the strain is less than 0.005 %. Compared with coating and bulk types, the sensor type could significantly improve the sensitivity, SNR and repeatability. Besides, the sensor type could eliminate the zero drift greatly and has little negative effect on the mechanical properties of samples.

Brane cosmology with variable tension

We study brane-world models and demonstrate that such models do not admit self-similar solutions through the matter collineation approach. By introducing the hypothesis of variable brane tension, λ, we outline the new effective field equation (EFE) in the most simple case (symmetric embedding) under the assumption that the fundamental constants in five dimensions (5D) are constants. In this case, we find the exact form that each physical quantity may take in order that the EFE become invariant under scale transformations. By taking into account such assumptions, we find that in four dimensions the gravitational constant κ2 ∼ λ, while the cosmological constant Λ ∼ λ2 is always decreasing. These results are quite general and valid for any homogeneous self-similar metric. Nevetheless, the study of the EFE under scale symmetries suggests that ρ ∼ λ (as a functional relationship). This allows us to get a growing κ2 but, in this case, the fundamental constants in 5D must vary as well. We outline a toy model allowing such a possibility.