Variation Of Tension Research Articles

Instabilities in a Spherical Liquid Drop

We examine cases of stationary vortices that can appear inside spherical liquid drops in microgravity conditions. The first case is that of an incompressible external flow of uniform speed at infinity, leading the liquid in the drop by friction to form a Hill vortex. In the second case, the external fluid does not interact by friction with the liquid, but the drop is subjected to an axial temperature gradient causing a variation in surface tension. This time it is the induced movement which entrains the internal liquid. Note that the two situations can lead to the same Hill vortex. Combined effects are envisioned. We are also interested in the time factor in these phenomena.

The Impact of Reduced Gravity on Oscillatory Mixed Convective Heat Transfer around a Non-Conducting Heated Circular Cylinder

The present analysis addresses the impact of reduced gravity and magnetohydrodynamics on oscillating mixed-convective electricallyconducting fluid flow over a thermal, non-conducting horizontal circular cylinder. In reduced gravity, buoyancy forces may induce fluid motion due to a weak gravitational field but in non-gravity forces, fluid motion can be induced by a variety of factors, including surface tension and density variations. The fluid motion is governed by connected nonlinear partial differential equations which are converted into convenient equations by applying a finite-difference scheme with the primitive transformation and a Gaussian elimination technique. The numerical solutions of the connected dimensionalized equations were obtained for various emerging dimensionless parameters, reduced gravity parameter Rg, Prandtl number Pr, and some other fixed parameters. First, the fluid velocity, temperature distribution and magnetic-field profiles were obtained and then these profiles were used to examine the oscillating quantities of skinfriction, oscillating heat transfer and oscillating rate of currentdensity. The FORTRAN software was used for the numerical results and these results were displayed on Tech Plot. The fluid velocity and magnetic profile were increased at the π/2 station as reduced gravity increased but the dimensionless temperature of the fluid attained a maximum magnitude as reduced gravity was decreased. The larger amplitude of the oscillating coefficients of τt and τm was concluded with a prominent variation for each λ in the presence of reduced gravity. Physically, this could be because an increase in the decreased gravity parameter impacts the fluid flow’s driving potential along a thermal, non-conducting horizontalcylinder.

A Compound Droplet Undergoing Thermocapillary Migration Passing Through a Constricted Tube

Abstract In this paper, we numerically investigate the dynamics of a compound droplet driven by surface tension variation induced by a thermal gradient in a sinusoidal constriction tube. Initially, the compound droplet with a concentric inner core is spherical and placed in the constriction's upstream region at a low temperature. As time progresses, it migrates downstream with a high temperature. Due to the constriction, the droplet is slowed down in the upstream region and accelerated again right after passing the constriction. This acceleration maximizes the eccentricity. However, the constriction results in an increase in the maximum eccentricity when increasing its depth to a value corresponding to the size of the tube neck, which is greater than or equal to the droplet size. Effects of various parameters, e.g., the Marangoni number Ma, the capillary number Ca, and the radius ratio Rio, are studied. It is found that increasing the Ma number or decreasing the Ca number reduces the maximum eccentricity and prolongs the travel time, i.e., the arrival time, from the upstream to the downstream. A similar reduction in the maximum eccentricity also occurs with the increased Rio ratio. Effects of these parameters on the migration velocity are also revealed.

Influences of fluid physical properties, solid particles, and operating conditions on the hydrodynamics in slurry reactors

Slurry reactors are popular in many industrial processes, involved with numerous chemical and biological mixtures, solid particles with different concentrations and properties, and a wide range of operating conditions. These factors can significantly affect the hydrodynamic in the slurry reactors, having remarkable effects on the design, scale-up, and operation of the slurry reactors. This article reviews the influences of fluid physical properties, solid particles, and operating conditions on the hydrodynamics in slurry reactors. Firstly, the influence of fluid properties, including the density and viscosity of the individual liquid and gas phases and the interfacial tension, has been reviewed. Secondly, the solid particle properties (i.e., concentration, density, size, wettability, and shape) on the hydrodynamics have been discussed in detail, and some vital but often ignored features, especially the influences of particle wettability and shape, as well as the variation of surface tension because of solid concentration alteration, are highlighted in this work. Thirdly, the variations of physical properties of fluids, hydrodynamics, and bubble behavior resulted from the temperature and pressure variations are also summarized, and the indirect influences of pressure on viscosity and surface tension are addressed systematically. Finally, conclusions and perspectives of these notable influences on the design and scale-up of industrial slurry reactors are presented.

Hydrodynamic characteristics of the crane vessel-three-bucket jacket foundation coupling hoisting system during the process of lowering

In the present study, a novel three-bucket jacket foundation with air-cushion launching technology is proposed. Through the theoretical analysis and commercial hydrodynamic software Moses, a crane vessel-three-bucket jacket foundation coupling hoisting system is established, and time-domain calculations are performed accordingly. Moreover, based on statistical information of the actual sea conditions in a certain sea area throughout the year, the corresponding permissible sea conditions for the construction of the sea are calculated to provide technical guidance for practical engineering. Furthermore, the hydrodynamic characteristics of the crane vessel, the motion response of the coupling hoisting system and variations of the cable tension under different configurations and wave directions are obtained. It is found that the vibration frequencies of the crane vessel and the foundation are the same, and the phase is maintained at 180°. It is considered that when the foundation is located at the stern of the vessel and encounters transverse waves, resonance occurs between the crane vessel and the foundation, which should be avoided in actual construction.

Modeling and optimization of Wire –EDM parameters for machining of Ni54.1Ti45.9 shape memory alloy using hybrid approach

Shape memory alloys are a distinct family of alloys recognized for their unique features, such as extreme anti-fatigue, exceptional specific strength, corrosion resistance, biocompatibility, and pseudo-elasticity. Due to strain-hardening effects displayed by the latter during a conventional machining process, these features make shape memory alloys particularly functional for machining utilizing non-traditional methods rather than conventional ones. The alloy's original qualities are at risk as a result of this consequence. Nickel-Titanium shape memory alloys with 54.1 and 45.9% Nickel-Titanium blends were employed in this investigation (Ni54.1Ti45.9). The surface characteristics of Ni54.1Ti45.9 alloy are investigated using the wire electrical discharge machining (WEDM) technique with a brass tool electrode (zinc-coated) and the influence of process parameters on it. Variations in wire feed rate, wire tension, pulse on and off duration, and peak current were used as input factors to investigate variations in surface roughness and material removal rate. Surface roughness and material removal rate data from L27 orthogonal array (OA) studies were used to create artificial neural network (ANN) models. To improve the quality attributes, a model combining a hybrid version of the genetic algorithm (GA) and an ANN has been presented. The ANN models were found to accurately predict the results, which matched the experimental data. After the adjustment, the quality features also improved significantly.

Influence of Initial Guy Tension and Antenna Masses in the Sensor Layout for Dynamic Characterization of Guyed Masts

Sensitivity analysis plays an important part in the validation of a sensor layout for the identification of the dynamic response of a system. Although sensitivity analysis has been implemented for this purpose in several civil engineering structures, there are still uncertainties in the case of more complex, nonlinear systems, such as guyed masts, where small changes in mass or stiffness can result in large variations of the general dynamic behavior. This paper describes the influence of antenna masses and initial guy tension variation in the total number and position of sensors required to assess the dynamic response of tall guyed mast telecommunication towers. For the study, the computational models of four different guyed masts were generated and a sensor layout was obtained for each model using a sensitivity analysis. Then, the proposed sensor layouts were verified for different initial guy tensions and total antenna mass of the system, by means of the Modal Assurance Criterion. The principal finding is that initial guy tension presents the highest influence on the variation of correspondence values between mode shapes, with modifications of these values in up to [Formula: see text]. This finding suggests that a preliminary sensor layout based on information provided by a computational model or structural drawings of a guyed mast may be rendered inefficient if there is variation in guy tension due to construction errors or relaxation of cables.

Experiment and prediction model study on pool boiling heat transfer of water in the electric field with periodically changing direction

The pool boiling heat transfer performance of water could be greatly improved by the constant electric field with the bar electrode. While, the heat transfer of water enhanced by electric field with periodically changing direction is rarely involved. Therefore, the heat transfer performance of water, mechanism analysis and prediction model for heat transfer characteristic affected by the electric field with periodically changing direction were studied. Individually, the heat transfer coefficient (HTC) and critical heat flux (CHF) were compared. Meanwhile, the difference of droplet shape, size of contact angle, bubbles growth and detachment on heat transfer surface were analyzed. Besides, semi-empirical prediction models for HTC and CHF were proposed. Results show that the HTC and CHF are significantly enhanced with decrease of switch period. While, this enhancement is diminished with increase of heat flux. Furthermore, when compared to the constant direction electric field, mechanism analysis indicates that the electric field with periodically changing direction not only enhances the rate of boiling fluid wetting the boiling heat transfer surface, but also accelerates the growth and detachment of bubbles. Moreover, predicted curves of model agree well with the experimental data, and variation of surface tension is considered as the main factor affecting heat transfer.

Improving the staircase approximation for wettability implementation of phase-field model: Part 2 – Three-component permeation

In this study, the displacement dynamics of compound droplet inside porous medium with complex structure is numerically investigated by the newly-proposed wetting boundary treatments in Part 1 [1]. The compound droplet consists of two immiscible fluids surrounded by another fluid forming a three-phase system. To investigate the compound droplet's penetration and spreading in two regimes, the conservative phase-field model is solved via the lattice Boltzmann method (LBM) at different wettability and governing non-dimensional numbers including the Reynolds number (25-100), Weber number (100-1000), and density ratio (7.5-750). Moreover, the permeation and spreading of each droplet, without the presence of the other in the binary system, is compared with those of ternary. It is revealed that the way the penetration is influenced by the variation of surface tension, wettability, and density ratio completely depends on the value of Bond number and the capillary or gravitational-dominant regimes. Furthermore, it appears that in the capillary-dominant regime, the migration pattern of one droplet cannot be evaluated independent of the other, since the factors affecting the capillary pressure and viscous coupling on one, affects the penetration and spreading of the other. Finally, it is identified that ternary penetration is slower than binary and the presence of the other droplet confines the early stage spreading in the ternary system.

Significance of non-intraocular pressure (IOP)-related factors particularly in normal tension glaucoma: Looking beyond IOP.

Purpose:To study the relationship between intraocular pressure (IOP) and mean ocular perfusion pressure (MOPP) in patients with POAG and NTG. The secondary objective was to identify other contributory ischemic factors.Methods:This was an observational cross-sectional study from a tertiary eye hospital in patients who underwent full-day diurnal variation of tension (DVT). Blood pressure (BP) and IOP measurements were done every 3 h over 24 h. Mean arterial pressure (MAP) and MOPP were calculated. The nocturnal dip in BP was assessed; patients were classified as non-dippers, dippers, and over-dippers. The circadian MOPP fluctuation (CMF) was calculated using the Kruskal–Wallis test, and its relationship with type and severity of visual field was assessed.Results:In total, 149 patients were evaluated; 109 were classified as NTG, and 40 were classified as POAG. A nocturnal dip in BP was noted in 20% of NTG and 17.5% of POAG. The MAP was found to be lower in patients with NTG than POAG. In the NTG subgroup, we found that 20% of patients were over-dippers, 32% were dippers, and 48% were non-dippers. The CMF showed a greater fluctuation for over-dippers (P = 0.004 for the RE and 0.003 for the LE) than dippers and non-dippers. A weak positive correlation of CMF with the severity of fields was found.Conclusion:A 24-h monitoring of IOP, BP, MOPP, and assessment of systemic risk factors for primary glaucoma acts as an invaluable tool for the comprehensive management of NTG despite the limitations posed by DVT and BP recording.

Simulation of Continuous Tension Stringing Process of Conductor with Bending Stiffness Model

At present, there is no research on the calculation of tension variation of the conductor with bending stiffness model between the continuous span during tension stringing construction. Aiming at the typical terrain with large elevation difference in UHV project, a vector finite element method for calculating the tension of the conductor with bending stiffness model passes through the pulley in the process of tension stringing is proposed. The process of the wire rope under the action of the tractor pulling the conductor passes through the pulley continuously is realized. The variations of tension of tensioner and tractor, reaction force of pulley and envelope angle of the conductor passes through the pulley are obtained by simulation of tension stringing conditions such as 1 pulls 1, 1 pulls 2, etc, which provides reference for equipment selection for the tension stringing construction of mountain terrain with large elevation difference.

Cover Feature: Catch and Release Chemotaxis (ChemSystemsChem 2/2022)

The Front Cover shows the repetition of catch and release chemotaxis, which was studied by using a self-propelled 6-methylcoumarin (6-MC) disk floating on water. A tablet of Na3PO4 placed at the bottom of the water phase acted as the chemical stimulus by inducing a variation in surface tension. The self-propelled object, the 6-MC disk, moves in the direction of the chemical stimulus (top left) and it is caught by the stimulus (top right), that is, by the chemical reaction between 6-MC and OH−. When OH− is consumed, the 6-MC disk is released from the tablet and moves towards the higher surface tension (bottom). More information can be found in the Article by Masaharu Nagayama, Satoshi Nakata and co-workers.

Morphology of MoS2 nanosheets and its influence on water/oil interfacial tension: A molecular dynamics study

Plate-shaped nanoparticles exhibit huge potential for a broad range of cutting-edge applications in interfacial-based science and technology, such as enhanced oil recovery in hydrocarbon reservoirs, owing to their remarkable features in superior affinity toward interfaces. Understanding the adsorption behavior of nanosheets (NSs) self-assembled at the water/oil interface (W/O interface) is crucial to elucidate the variation of interfacial tension (IFT) and establish special design criteria for efficient industrial use of NSs. Here we present a molecular dynamics study to reveal the morphology of carbon-chain modified molybdenum disulfide (MoS2) nanosheets. The stress exerted on a nanosheet is analyzed. The simulation results demonstrate a significant decrease in interfacial tension after adding NSs to the water/oil system, followed by a noticeable fluctuation with increased NS concentration. Surprisingly, the carbon-chain modified MoS2 nanosheets do not show a greater ability in altering IFT compared to unmodified ones. The IFT fluctuation is found strongly linked to the competition between the effects of interface coverage rate of adsorbed nanosheets and the intersection angle arising from non-uniform forces acting on a nanosheet.

Surface roughness effects on a tensioned riser vortex-induced vibration in the uniform current

Due to the long-term operation of marine riser, marine organisms will adsorb on its surface, thus affect its surface roughness. The surface roughness of the riser will affect the wake flow field of the riser, and then affect the dynamic characteristics of the vortex-induced vibration (VIV). The study of the influence of surface roughness on the characteristics of a rough riser VIV is helpful to improve our understanding of the mechanism of a rough riser VIV and ensure the safety of the riser during its service life. Based on the methods of computational fluid dynamics (CFD) and computational structure dynamics (CSD), this study presents the model considering tension variation with the structure vibration and the modified model of rough wall velocity gradient to construct the numerical calculation program of a rough riser VIV to study effects of various key parameters (surface roughness, inflow velocities) on the dynamic characteristics, vibration response, wake vortex shedding patterns and vibration trajectories of a rough riser. The results show that in the range of Reynolds number Re = 2.515 × 104∼1.258×105 and reduced velocity U* = 1.35–6.74, compared with a smooth riser, the streamwise vibration amplitude of a rough riser decreases, and with the increase of inflow velocity and surface roughness, the streamwise vibration amplitude of a rough riser decreases more and more obviously. In the range of reduced velocity U* = 2.70–5.39, the transverse vibration amplitude of a rough riser increases slightly. At a higher reduced velocity (U* = 6.74), the transverse vibration amplitude of the rough riser decreases. Larger surface roughness will enhance the multi-frequency and broadband vibration characteristics of the riser in the streamwise direction. With the increase of surface roughness, the multi-frequency vibration characteristics decrease gradually, but the broadband vibration characteristics increase gradually in the transverse direction. Surface roughness can suppress 2T and 2P wake vortex shedding pattern and enhance 2C wake vortex shedding pattern. This study will provide a profound understanding to guide the practical marine riser VIV research with the consideration of surface roughness.

Field observation of galloping on four-bundled conductors and verification of countermeasure effect of loose spacers

This paper describes the galloping occurrence conditions of four-bundled conductors and the galloping suppression effect of diagonally arranged loose spacers, which is a type of spacer applicable for four-bundled conductors with two rotational clamps placed at diagonal positions. Field observations were conducted at a full-scale test line in Japan where in-cloud icing frequently occurs. A total of 40 ice accretion events were observed across four winter seasons, and galloping data were obtained in a non-countermeasure phase set with normal spacers and a countermeasure phase set with loose spacers. The relationship between the total displacement amplitude and tension variation was determined to identify the conditions under which large galloping occurred based on tension data, in addition to the displacement data. Galloping was found to occur at wind speeds exceeding 9 m/s, and large galloping oscillations were observed when a certain relationship was satisfied between the wind speed and the amount of ice accretion. Furthermore, it was observed that the loose spacers reduced the galloping oscillation amplitude by approximately 40%. The rotational clamps operated normally under severe natural conditions, and the suppression effect was caused by the difference in the ice accretion characteristics of the rotatable subconductors owing to their rotation.

Surface tension and parachor for a new low-GWP refrigerant R1123/R32/R1234yf and its constituent binary pairs

Trifluoroethene R1123 is expected to be a low GWP refrigerant; however, it needs to be mixed with other stable refrigerants to avoid a disproportional reaction. This paper delivers one of the essential thermophysical properties surface tension for a low-GWP refrigerant mixture R1123/R32/1234yf measured by the differential capillary rise method in the temperature range from 225 to 345 K. The propagated uncertainty in surface tension with a 95% confidence level was typically 0.15 mNm−1. From the measured surface tension and calculated saturation densities, the parachor of R32 and R1123 were determined to be 91.6 and 123.3, respectively. The parachor of R1234yf was slightly dependent on a temperature, T, as 181.44−0.0319T. The variation in the surface tension of binary pairs against the composition was predicted by the correlation proposed by Di Nicola et al. (2018) and the parachor method with sufficient accuracy. Furthermore, the surface tension of ternary mixture R1123/R32/1234yf at compositions of 60/22/18 mass% and 22/70/08 mass% was also predicted by the parachor method with sufficient accuracy. Nevertheless, a slight deviation was confirmed at temperatures below 260 K. The prediction would be improved with subsequent studies in phase equilibrium. (191 words).

A natural source of saponin: Comprehensive study on interfacial properties of Chubak (Acanthophyllum Glandulosum) root extract and related saponins

Chubak (Acanthophyllum Caryophyllaceae) is a shrubby plant with saponin-rich roots. This feature makes this plant to a new source of natural surfactant. This article presents some basic information about the surface activity of Chubak root extract (CRE) and the corresponding purified saponin. The Calendasaponin B and Calendasaponin D were characterized in the purified saponin using Liquid Chromatography-Mass Spectrometry as the two main saponins. The dynamic surface tension and dilational surface visco-elasticity of CRE and the purified saponin were studied using a profile analysis tensiometer. The equilibrium surface tensions of CRE and the purified saponin in the concentration range up to the CMC show that the used purification method is not efficient to separate the complete saponin content of CRE. The surface activity of CRE started at 0.005 g/l, while the minimum saponin concentration for a first visible surface tension decrease was 0.0012 g/l. The uniform trend in surface dilational elasticity and viscosity of CRE and the purified saponin is the evidence for the similarity of dominant surface-active compounds in both samples. Comparing the short time surface tension of oscillating and steady drops showed the impact of adsorption layer oscillations on the surface tension variations.

STUDY OF THE VARIATION OF SURFACE TENSION OF DIFFERENT COMPOUNDS DISSOLVED IN WATER DURING THE COVID PANDEMIC

A study of the variations in the surface tension of distilled water caused by alcohol, salt and saponin in different concentrations and mixtures is carried out. As a consequence of the difficulties arising from the pandemic, the study was elaborated in such a way as to make it feasible to realise at home. The Du Nouy method was applied, using a balance and a dynamometer as measuring systems, which were assembled with materials collected at home and purchased in book or hardware stores. It was observed that in the case of alcohol and saponin the surface tension decreases and that in the case of salt and a mixture of saponin and salt, it first decreases and then increases. Precise measurements of the systems were obtained with percentage errors of 11.3 % and 1.2 % for the dynamometer and the balance, respectively.

Endocytosis and exocytosis protect cells against severe membrane tension variations

The ability of cells to regulate their shape and volume is critical for many cell functions. How endocytosis and exocytosis, as important ways of membrane trafficking, affect cellular volume regulation is still unclear. Here, we develop a theoretical framework to study the dynamics of cell volume, endocytosis, and exocytosis in response to osmotic shocks and mechanical loadings. This model can not only explain observed dynamics of endocytosis and exocytosis during osmotic shocks but also predict the dynamics of endocytosis and exocytosis during cell compressions. We find that a hypotonic shock stimulates exocytosis, while a hypertonic shock stimulates endocytosis; and exocytosis in turn allows cells to have a dramatic change in cell volume but a small change in membrane tension during hyposmotic swelling, protecting cells from rupture under high tension. In addition, we find that cell compressions with various loading speeds induce three distinct dynamic modes of endocytosis and exocytosis. Finally, we show that increasing endocytosis and exocytosis rates reduce the changes in cell volume and membrane tension under fast cell compression, whereas they enhance the changes in cell volume and membrane tension under slow cell compression. Together, our findings reveal critical roles of endocytosis and exocytosis in regulating cell volume and membrane tension.

Comparative study of external electric field and potential effects on liquid water ions

Molecular dynamics simulations were used extensively in the last decades to study the influence of an external electric field on many physical processes in water, including mobility of ions, field-induced vaporisation, and electrowetting. In most of these studies, the electric field was applied as an external force to all atoms in the simulation. While such an approach is intuitive and straightforward, it neither captures the shielding of the electric field by water nor any interfacial effect. The Constant Electrode Potential Method (CPM) allows for an external electric field to be applied on a system level, resembling experimental settings and accounting for shielding effects by water. In this work, the CPM method has been implemented to study the influence of an external electric field on the surface tension of water and to compare that to the conventional method, in addition to computing the interfacial mobilities of Na+ and Cl− ions at a liquid–vapor interface. The two approaches yield a similar trend of surface tension variation with the electric field. The CPM method predicts a weaker variation in the surface tension in comparison to that of the conventional method, with the maximum reported difference being 36% of the surface tension value.