Time-dependent Viscosity Research Articles

The atmospheric Ekman flows with time-dependent eddy viscosity

In this paper, we consider nonsteady modified atmospheric Ekman equations in the f−plane approximation. We non-dimensionalize the equations of the motion in the f−plane. For two types of time-dependent eddy viscosity, by means of Laplace transform, we get the explicit formulas, respectively.

Diffusion mechanism of fracture grouting in rock mass with flowing water

Grouting is a widely used geotechnical procedure known for its strong empirical properties. It has been extensively utilized for sealing subterranean water and strengthening soil and rock masses in their original locations in underground mining and underground space development. The diffusion mechanism of grouting in fractured rock is affected by the geological environment and slurry performance, which should be better revealed and characterized. In this paper, we take the surrounding rock of the roadway as the research object, consider the stress condition of the injected rock and time-dependent viscosity of the slurry, and establish fracture grouting diffusion model based on the rock composite fracture criterion. The grout strengthening mechanism is discussed based on a transparent fracture replica grouting test. According to the different transport characteristics of the slurry interacting with flowing water, it is divided into the following four areas grout-water balance area, grout loss area, stagnation area and water passage. The grout plugging mode is divided into two categories according to its final diffusion pattern: cross-section type water plugging mode and water-drop plugging mode. The pressure monitoring data of the test verified the two grout plugging modes. The diffusion distance of cis-reverse water derived in this study was in good agreement with the experimental results in grouting early stage. The research results can provide a theoretical basis for grouting engineering design.

Development of transparent soil grouting test system and its application in grouted gravel pile

To visualize the grouting process of grouted gravel piles, a transparent soil model test system was developed. This system allows for the study of soil movement around the piles during grouting reinforcement and enables load-bearing capacity testing after grout solidification into piles. The experimental system comprises a grouting system, a vertical load-bearing capacity testing system, a continuous physical field measurement system, and a model box. The grouting system facilitates sequential processes: pre-consolidation, constant-pressure grouting, and vertical loading. In transparent clay with a pre-consolidation pressure of 60 kPa, constant-pressure grouting and vertical load-bearing tests for grouted gravel piles were conducted. The results captured the disturbance deformation of the soil around the pile during both grouting and vertical loading. The study indicates that disturbance deformation of the soil surrounding the pile increases with prolonged grouting time. Soil beneath the pile end predominantly undergoes vertical compression, while soil at the pile sides experiences horizontal compression. The mid-section of the soil adjacent to the pile displays oblique upward bulging and vertical deformation. Under constant-pressure grouting, the filling rate of gravel voids in the pile hole by epoxy resin chemical grout with strong time-dependent viscosity shows a decreasing trend. During vertical loading, the displacement of the soil around the pile is significantly greater than that at the pile end. Consequently, this test system facilitates the visualization and simulation of grouting and vertical load-bearing tests for grouted gravel piles.

Thermal energy enhancement in blood conveying gold nanoparticles with temperature-dependent viscosity

Cancer is one of the universal popular healthcare problems, and there is a struggle to find advanced fresh medicines andidentify superior ways of distributing medications. Cancer is harmful and deadly to maximum of its patients. Cytotoxic agents are carried by cancer cells, to increase efficacy and protection. This reminds us that nanotechnology can be utilized for medicine. This current allegation has built into gold nanomaterials which could conquer and heal — it being the material considered like gold (atomic number 79). It gives a large amount of heat and contributes to the therapy of malignant tumors. Therefore, it is urgent to investigate the flow of blood-based gold nanoparticles over the porous medium for injection/suction effects. Time-dependent viscosity was used in Reynolds exponential model. The existence of magnetic field and nonlinear thermal radiation was integrated into the system. Ensuing equations were interpreted by its nondimensional model by applying comparison renovation. This Lobatto IIIA formula (known as bvp4c) was working to acquire multiple solutions. This findings indicate that temperature increases due to magnetic and radiation effects. Temperature and velocity profiles by injection are greater although related to the suction phenomenon. Further, the temperature and velocity augment by the inclusion of gold nanoparticles into blood flow.

Effect of M/P ratio, w/c ratio, and additive contents on rheological properties of seawater mixed magnesium phosphate cement system

Rheological properties play a crucial role in determining the grouting effectiveness of magnesium phosphate cement (MPC) slurry. This study aims to investigate the effects of the magnesia-to-phosphate (M/P) ratio, water-to-cement (w/c) ratio, fly ash (FA), and metakaolin (MK) on the rheological properties of seawater-mixed MPC slurries using rheological tests and low-field 1H nuclear magnetic resonance (NMR). Two methods for incorporating FA were explored to modulate the rheological properties of the MPC. The results demonstrated time-dependent viscosity changes with two distinct phases, including a plateau and a subsequent period of sudden change, with the minimum apparent viscosity occurring as hydration progressed. The apparent MPC viscosity was influenced by the MgO-particle content and the theoretical water consumption, with M/P = 3 exhibiting the lowest apparent viscosity within a w/c range of 0.14–0.2. Moreover, the addition of FA increased the minimum apparent viscosity of the MPC slurry. During the pre-hydration stage, using FA as an MPC substitute yielded better rheological properties than using FA as an MgO substitute. The MK increased the apparent MPC viscosity considerably and adversely affected its rheology.

Riemann problem for a general variable coefficient Burgers equation with time-dependent damping

In this paper, we study the Riemann problem for a general variable coefficient Burgers equation with time-dependent damping. We use a nonlinear time-dependent viscosity equation with a similarity variable. Thus, when the viscosity goes to zero, we obtain Riemann solutions to the general variable coefficient Burgers equation with time-dependent damping. Moreover, we use the Lax–Friedrichs scheme to obtain numerical evidence of the Riemann solutions.

Penetration mechanism of grouting by using the cement-based slurry with time-dependent viscosity

Penetration mechanism of grouting by using the cement-based slurry with time-dependent viscosity

Analytical Studies of Fluid Conveying Pipes on Viscoelastic Foundation Using Differential Transforms Method

This study presents an analytical investigation of the vibration of fluid-conveying pipes on viscoelastic foundations using the differential transform method. The effects of a new time dependent viscosity parameter in the modified Winkler viscoelastic foundation is studied and analyzed. The governing equation is a fourth-order partial differential equation with pinned-pinned boundary conditions, which required a special analytical method for solution. The differential transform method was applied to obtain the solution of the governing partial differential equation for the fluid-conveying pipes on viscoelastic foundations. The time-dependent viscosity parameter in the modified Winkler viscoelastic model was implemented and simulated to determine the behavior of the viscoelastic foundation. The obtained analytical solution was validated with Runge-Kutta order four numerical method. The effects of foundation stiffness , coefficient of foundation damping and the frequency mass ratio on the governing model equation were investigated. In addition, the bending and deflection of the pipe on a viscoelastic foundation are compared with those on an elastic foundation. The analytical and the numerical solutions are in good agreement. From the study, it is observed that an increase in the foundation stiffness results in increase in the pipe inherent frequencies. Furthermore, the vibration of the pipe on a viscoelastic foundation shows better control and reduction compared with its vibration on an elastic foundation.

Propagation Analysis of Polymer Grout in Vertical Fractures: An Experimental and Numerical Study

The use of non-aqueous reactive polymer grouting is a proven technique for preventing gravity erosion in Pisha sandstone through the filling of vertical fracture. However, the diffusion behavior of the polymer grout within vertical fractures remains unclear and requires further investigation for effective grouting design. This study conducts laboratory experiments to examine the effects of grouting quantity on the spread pattern, diffusion distance, and pressure distribution of polymer grout within a visual vertical fracture. The maximum pressure is 6.25 kPa for a grouting quantity of 120 g, 7.5 kPa for 227 g, and reaches about 9.4 kPa for a quantity of 350 g. A numerical model, incorporating time-dependent density and viscosity, is then developed and validated using experimental results. Finally, the influence of initial viscosity 0.05 Pa·s, 0.1 Pa·s, and 0.5 Pa·s on the flow pattern of polymer grout within the vertical fracture is analyzed. The results show that initially gravity causes a dominant downward flow of polymer grout in a vertical fracture. However, as the grout expands due to the chemical reaction, it propagates in all directions. Furthermore, the gravity causing the dominant downward flow of polymer grout decreases with increasing initial viscosity, and the diffusion distance increases in the horizonal direction but decreases in the vertical direction. On this basis, suggestions for optimal grouting hole arrangement are provided to enhance grouting design.

Multiphase flow coupling analysis of shield synchronous grouting filling law with time-dependent viscosity

Owing to the non-visual characteristics of the shield synchronous grouting engineering, the law of grout filling in the shield tail gap remains obscure. There is a current deficiency in effective three-dimensional filling and diffusion models. Building upon a large-diameter, eight-hole shield tunneling grouting project in Hangzhou, this study aims to construct a holistic three-dimensional model of grout filling in the shield tail gap. Employing COMSOL Multiphysics and grounded on the two-phase Navier–Stokes equations, this study simulated the filling of grouting fluid in the shield tail gap. Utilizing the Brookfield DV3T rheometer, the study ascertained the time-dependent expression of grout viscosity and systematically analyzed the impacts of time-dependent grout viscosity, density, and injection pressure on the filling diffusion morphology, pressure field, velocity field, and the buoyancy experienced by the segmental lining. The results indicate that the injection pressure is positively correlated with the circumferential pressure field of the segmental lining, though the influence on the ring's total buoyancy is minimal. The rate of grout viscosity development significantly affects the overall diffusion morphology: conventional grout tends to be underfilled at the top of the shield tail gap while rapid-setting grout is more likely to be underfilled at the bottom. The grout density is positively correlated with the grout displacement speed and the total buoyancy of the segmental lining. In light of these insights, utilizing low-density, rapid-setting grout under high-pressure grouting for shield tail filling can ensure adequate filling rates while mitigating the adverse effects of segment buoyancy.

Viscoelastic third-order nanofluid MHD flow for wire coating purpose inside canonical coating die with variable viscosity effect: numerical and analytical solutions

The polyethene coating is frequently functionalized to cables or pipes for corrosion prevention, voltage differential, mechanical characteristics, and environmental legislation. The metal coating technique, in particular, is important in a variety of commercial applications. Coaxial extrusion, immersion, and electromagnetic application are examples of wire surface treatments. The wire coating procedure necessitates an increase in thermal performance. As a result, this research aims to determine how floating nanoparticles affect the mass and heat transport mechanisms of non-Newtonian fluid in the posttreatment for cable coating processes. For nanofluids, the Buongiorno model is used, including variable viscosity. The original mathematical formulation in terms of nonlinear ODEs for bvph2 is altered to first-order ODEs using similarity transformation. The data collection for the projected bvph2 is developed for variables related to the proposed model manipulating the velocity consuming the explicit bvph2 technique. The exercise, confirmation, and analysis processes of the ND-solve method are utilized to appraise the attained results of bvhp2 for numerous cases, and an assessment of the achieved consequences is executed with available statistics set to pattern the correctness and efficiency of the suggested algorithm for the scrutiny of non-Newtonian fluid problem connected bvph2. The prevailing uniformity of recommended conclusions with published findings designates the legitimacy of the structure, and the accurateness of 10−6 is also accomplished. The analytical findings of this investigation revealed that within the Reynolds modeling, the stress on the whole wire surface combined with shear forces at the surface predominates Vogel’s model. The contribution of nanomaterials upon force on the entire surface of wire and shear forces at the surface appears positive. A non-Newtonian feature can increase the capping substance’s velocity. This research could aid in the advancement of wire coating technologies. For the first instance, the significance of nanotechnology during wire coating evaluation is explored by utilizing Brownian motion with generation/absorption slip processes. For time-dependent viscosity, two alternative models are useful.

Rheological properties of CEMI type microfine cement slurry with different fineness

In geotechnical engineering, rheological properties of CEMI type microfine cement slurries are deficient. In this paper, rheological performance of microfine cementitious slurry is studied systematically under five particle fineness, five water-binder ratios (W/B), and different contents of superplasticizers (SP) (naphthalene-based (N) and polycarboxylate-based (PCE)). Rheological performance included rheological behavior (fluidity and flow time), key parameters (yield stress, plastic viscosity, and hysteresis area), and time dependent viscosity. Their correlations and reasons were discussed. The results showed that rheological parameters did not change significantly when the W/B is greater than 1.5. For MCIV slurry without SP, when the W/B increased from 1.5 to 2.0, yield stress decreased from 2.3 to 1.53 Pa, plastic viscosity decreased from 8 to 4.5 mPa·s, and hysteretic area is reduced from 466.6 to 206.8 Pa/s. The W/B affects rheological parameters significantly compared with the fineness. The critical rheological model transformation condition of MCII slurry was determined when W/B was 1.2 without SP. For MCIII and MCIV grouts with W/B of 1.0, rheological parameters of slurries with 0.3% PCE are close to those with 0.7 % N. Quantitative relationships among rheological parameters and behavior were established, and correlations were determined. Moreover, relationships among apparent viscosity and W/B, fineness and time are established. To ensure grouting effectiveness in applications, a combination of W/B of 1.0–1.5, MCIII or MCIV fineness, 0.3–0.4% PCE or 0.5–0.7 % N is suggested.

Angular momentum and lithium transport from main sequence to sub-giant and red giant low-mass stars

Context. Asteroseismology provides a unique opportunity to probe the interiors of evolved stars and constrain their internal rotation. The correct reproduction of the core rotation evolution has not yet been achieved, although it is key to understanding the internal processes involved in low-mass stars. Aims. We explore the efficiency required to reproduce the general behaviour of the transport of angular momentum along the evolution in view of asteroseismic constraints from giant low-mass stars. We analyse the consequences and predictions for lithium and beryllium surface abundances from the main sequence to red giant phase. Methods. We computed a series of models, which included atomic diffusion, rotation-induced mixing, magnetic braking, and additional processes tailored for main sequence low-mass stars. We extended these models to more evolved phases and investigated an updated angular momentum transport by including a time-dependent extra viscosity related to the azimuthal magneto-rotational instability. We compared our predictions to the asteroseismic measurements of the core and surface rotation of a sample of sub-giant and red giant stars. We compared the model predictions for the lithium and beryllium surface evolution with the available observations. Results. We confirm that a time-dependent additional viscosity νadd(t) is required to reproduce the general behaviour of the core rotation rate along successive stellar evolutionary phases given the dependence on the differential rotation and the mass. We show that it results in stronger lithium and beryllium depletions for low-mass stars over evolution. We confirm that predicted lithium abundances at the red giant bump by classical models, commonly used as references, cannot reproduce the lithium depletion along the main sequence and evolved phases of stellar evolution. We show that the observed amount of lithium of stars less massive than 1 M⊙ leads to a discrepancy between model predictions and observations at the red giant bump. Conclusions. We show that a semi-parametric model can reproduce the rotational behaviour along the first phases of evolution well, with the exception of the sharp transition observed during the sub-giant phase. This suggests that two distinct transport processes may be involved. The processes required to transport chemicals during the main sequence phase and angular momentum until the red giant phase impact the lithium depletion all along the evolutionary duration. A good prediction of the lithium abundance at young phases places strong constraints on the predicted one at more evolved phases. It also highlights discrepancies between models and observations for the lowest mass stars and impacts the threshold that defines lithium-rich giant stars, showing that classical models tend to overestimate this threshold.

Shear influence on colloidal cluster growth: a SANS and USANS study.

This study examines the time evolution of silica/water clusters where the formation of a gel network from unitary silica particles is interrupted by a simple Couette shear field. The aim is to enable the general understanding of this simple system by examining the microscopic basis for the changes in viscosity by providing structural inputs from small-angle scattering for a simple theoretical model. The experimental system is an 8.3 nm particle silica solution (Ludox) where the gelation has been initiated by lowering the pH in a Couette cell providing a constant shear rate of 250 s-1. A unified small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) procedure is described to measure the scattered intensity in a wavevector range of 3 × 10-4 ≤ q (nm-1) ≤ 3.1 × 10-1, probing structural changes over a broad range of length scales from the nanometre to the micrometre. Scattering data provide a new means of better understanding the behaviour of colloidal clusters when subjected to an external applied shear over a continuous time sequence after gel initiation; a fit of the time-dependent scattered intensity leads to an estimation of the cluster's effective volume fraction and size as a function of time. A reductionist theoretical basis is described to predict the time-dependent viscosity behaviour of the sheared colloidal suspension gel-initiated cluster growth from the volume fraction of the clusters.

Time and temperature dependent magnetic viscosity experiments on Sr/Co nanoferrite particles

Magnetic viscosity experiments have been performed in order to investigate the magnetization reversal in Sr nanoferrite particles (nanoscale SrFe12O19) and interacting Sr/Co nanoferrite particles (SrFe12O19–CoFe2O4 nanocomposites). The magnetic viscosity S = d M ( t ) / d l n ( t ), where M ( t ) is the magnetization as a function of time, has been collected. For Sr nanoferrite S shows a maximum close to the coercive field, reflecting the relation between S and the energy barrier distribution. We evidence that magnetic viscosity experiments on Sr nanoferrite and interacting Sr/Co nanoferrite particles provide reliable qualitative results for the different magnetic field sweep rate and saturating field H s a t considered. In addition, the activation volumes extracted from the magnetic viscosity experiments performed at different temperatures on Sr nanoferrite are quantitatively correlated to anisotropy changes.

Bioconvective flow of a variable properties hybrid nanofluid over a spinning disk with Arrhenius activation energy, Soret and Dufour impacts

This paper explores the heat and mass transfer by hybrid nanofluids flow over a spinning disk in the presence of oxytactic microorganisms. During this study, the Soret and Dufour together with Lorentz force impacts are considered. The worked nano-mixture is assumed to be having time-dependent dynamic viscosity and thermal conductivity and its components are methanol-based hybrid nanofluid comprising CuO and MgO nanoparticles. The disk surface is permeable and various aspects such as thermal radiation, heat generation and Arrhenius activation energy are taken into account. The governing equations are treated numerically and suitable similar transformations are introduced. The obtained results revealed that both of the velocity and temperature gradients are enhanced as the absolute values of unsteadiness parameter and nanoparticles concentrations are rising. However, the flow is slowdown as the temperature-dependent variable viscosity parameter is growing.

Postglacial relative sea-level changes in the Gulf of Maine, USA: Database compilation, assessment and modelling

Relative sea level (RSL) reconstructions from paleo records are often the most valuable data set for testing and constraining glacial isostatic adjustment (GIA) models. In some regions, the amplitude and rate of the reconstructed RSL changes are large making the data difficult to fit. Arguably, the reconstructed RSL curve from Maine, USA, is the classic example of such a data set with peak values at about 120 m dropping to a low stand of around −40 m within a few thousand years. To our knowledge, no GIA model has captured these extreme variations and the record has been somewhat neglected by the GIA modelling community. Here we critically assess and present a revised pre-10 ka RSL data base for this region and combine it with two recent Holocene compilations. Based on our assessment, we conclude that the large and rapid changes, inferred in previous studies, are robust. To determine if a successful model fit can be found, we consider a GIA parameter set comprising five ice models and 440 spherically-symmetric, Earth viscosity models assuming a Maxwell rheology. Results show that none of the model parameter sets produce a good fit to the data set. The rapid RSL fall and lowstand can be simulated by Earth models with low values of upper mantle viscosity (∼5 × 1019 Pas). However, such low viscosity values result in a large mid-Holocene highstand (order 10 m) while the observations indicate a monotonic RSL rise throughout this interval. Our results indicate that Earth models able to simulate time-dependent viscosity (i.e., those that include transient and/or non-Newtonian deformation) might be required to fit the Maine RSL data set.

Exploring bulk viscous unified scenarios with gravitational waves standard sirens

ABSTRACT We consider the unified bulk viscous scenarios and constrain them using the Cosmic Microwave Background observations from Planck 2018 and the Pantheon sample from Type Ia supernovae. Then we generate the luminosity distance measurements from ${\cal O}(10^3)$ mock Gravitational Wave Standard Sirens (GWSS) events for the proposed Einstein Telescope. We then combine these mock luminosity distance measurements from the GWSS with the current cosmological probes in order to forecast how the mock GWSS data could be effective in constraining these bulk viscous scenarios. Our results show that a non-zero time dependent bulk viscosity in the universe sector is strongly preferred by the current cosmological probes and will possibly be confirmed at many standard deviations by the future GWSS measurements. We further mention that the addition of GWSS data can significantly reduce the uncertainties of the key cosmological parameters obtained from the usual cosmological probes employed in this work.

Comparison of time-dependent viscosity slurry and cement-clay slurry for anti-seepage grouting on faults

The complex rock mass structure in fault fracture zone weakens the permeability of strata. This has led to curtain grouting being used to improve the anti-seepage properties of fault zones. This study evaluates the groutability and impermeability of a time-dependent viscosity slurry and a cement-clay slurry in a shattered fault zone. Rheology, setting time, mechanism, and permeability were tested to evaluate the groutability, and Lugeon and grouting field tests were carried out to evaluate the anti-seepage grouting characteristics of a fault zone. The results show that the time-dependent viscosity slurry had higher initial fluidity, a shorter and more controllable setting time, and higher strength than cement-clay slurry, better ensuring the slurry diffusion radius, pores filling rate, and bearing capacity and durability of the consolidated body. The permeability coefficient of the two grouts was less than 1×10−7 cm/s, and the blocking rate of heavy metal ions was more than 98%, sufficient to effectively control the leakage of sewage. The P∼Q curve of the Lugeon test showed that the original strata were of the washout type (>200 Lu), and the rock mass quality grade was the D grade (Poor). Under the same grouting depth, the amount of time-dependent viscosity slurry required was 72.6% of that of cement-clay slurry, and the permeability decreased to 10 Lu, far lower than the 50 Lu of the cement-clay slurry. The time-dependent viscosity slurry improved the quality of the rock mass from D to B-C grade, while the cement-clay slurry test area is remained C-D grade. In general, the time-dependent viscosity slurry performed better than cement-clay slurry in the water-bearing fault zone.

Bulk Viscous Flat FLRW Model with Observational Constraints in f(T, B) Gravity

This paper investigates the impact of bulk viscosity within the framework of f(T,B) gravity. We consider a time-dependent viscosity model with a particular Hubble parameter expression. Here, we looked into the viability of well-motivated f(T,B) gravity model, which takes the form f=αlog(B)+βT, and has free parameters α and β. The 46 observational Hubble data (OHD) in the range 0≤z≤2.36 were used to constrain the model parameters to achieve the solution. We have used the Markov Chain Monte Carlo (MCMC) method to estimate model parameters and observe that the model appears to be in good agreement with the observations. In addition, we evaluate the effective viscous equation of state parameter for the f(T,B) model. We have examined the characteristics of different energy conditions for the stability analysis. The model is valid based on the positive behavior of null energy conditions (NEC), weak energy conditions (WEC), and dominant energy conditions (DEC); however, strong energy conditions (SEC) are in violation, suggesting that the universe is expanding faster. Our model was found in the quintom region. We also discussed how the tachyon scalar field corresponds to f(T,B) gravity.