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In this paper, three real fluid mixtures, such as methane+Ar, methane+Kr and methane+Xe, are considered and the viscosity of the mixtures is theoretically calculated. For this purpose, three potential models are chosen. The potential models have the same repulsive terms but different attractive parts. The main purpose of this paper is to study the contribution of the potential attractive term on the viscosity of the fluid mixtures. To this goal, the Ornstein–Zernike (OZ) integral equation is first solved. Then, the viscosity is calculated by the Vesovic–Wakeham (VW) formalism. The obtained results in this work have been compared with the simulation data and also the experimental results. The findings show that the viscosity at low density for the three potential models is in good agreement with the simulation data. But, at high density, one of the potential models gave better agreement with the experimental results. Also, it is found that for each of the aforementioned mixtures, only one potential model gives a better result in comparison with the experimental data. The lowest deviation with the experimental data corresponds to the mixture of methane+Kr (3.0%) and methane+Xe (3.0%) by using different potential models. It means that the attractive term has an important role in predicting the viscosity of the fluid mixtures.

The viscosity of the eight binary systems (Cu–X ($\mathrm{\text{X}}=\mathrm{\text{Ag}}$, Al, Sn, Mg) system and Ag–X ($\mathrm{\text{X}}=\mathrm{\text{Sn}}$, Sb, In, Au)) was re-assessed, employing a new CALPHAD-type equation model proposed in our previous work. The calculated viscosities of the binary alloys were compared with the experimental data. It was found that this CALPHAD-type equation is very effective in fitting with the experimental data. Therefore, this work proves the validity of our new CALPHAD-type equation model for accurate viscosity predictions in alloys with varying component compositions.

The phase-separating system coupled with a simple reversible reaction A ⇌ B in a binary immiscible mixture due to critical quench is investigated with Lowe-Andersen temperature controlling method in two dimensions. The system viscosity strongly influences the asymptotic relationship between the excess energy (characterizing the domain growth) and the reaction rate. The competition between different dynamic factors results in the steady states with characteristic domain sizes. For low viscosities, the domain growth exponent approximates to 0.4 in the cases of low reaction rates and to 0.25 in the cases of high reaction rates, which shows the suppressing effects of high reversible reaction rates on the phase separation. However, in the cases of high viscosities, we find a 0.25 scaling with low reaction rates but a 0.5 scaling with high reaction rates. In these cases, high viscosities prevent mass transport in the binary mixture, consequently result in much smaller steady state domain sizes. Therefore the domain sizes with high viscosities and low reaction rates are very similar to those with low viscosities and high reaction rates, and the dependence of domain sizes on the reaction rates are similar. For the high-viscosity systems with high reaction rates, the domain sizes are predominantly controlled by the reaction rates, therefore we can observe stronger dependence of domain size on the reaction rate.

We present here a comparison between collision-streaming and finite-difference lattice Boltzmann (LB) models. This study provides a derivation of useful formulae which help one to properly compare the simulation results obtained with both LB models. We consider three physical problems: the shock wave propagation, the damping of shear waves, and the decay of Taylor–Green vortices, often used as benchmark tests. Despite the different mathematical and computational complexity of the two methods, we show how the physical results can be related to obtain relevant quantities.

This work aims to assess the response of viscoelastic Kelvin–Voigt microscale beams under initial stress. The microbeam is photostimulated by the light emitted by an intense picosecond pulsed laser. The photothermal elasticity model with dual-phase lags, the plasma wave equation and Euler–Bernoulli beam theory are utilized to construct the system equations governing the thermoelastic vibrations of microbeams. Using the Laplace transform technique, the problem is solved analytically and expressions are provided for the distributions of photothermal fields. Taking aluminum as a numerical example, the effect of the pulsed laser duration coefficient, viscoelasticity constants and initial stress on photothermal vibrations has been studied. In addition, a comparison has been made between different models of photo-thermoelasticity to validate the results of the current model. Photo-microdynamic systems might be monolithically integrated on aluminum microbeams using microsurface processing technology as a result of this research.

The shear viscosity of quark–gluon plasma (QGP) at leading logarithm order at finite temperature and chemical potential in weakly coupled limit is studied by solving transport equations. The result shows that the chemical potential effect adds a positive μ²/T² correction to the pure temperature case and thus increases the shear viscosity.

In this paper, motivated by Ref. 31, we study the so-called new agegraphic Chaplygin gas model with viscosity. Concretely, we establish the correspondence between the interacting new agegraphic dark energy (NADE) and variable generalized Chaplygin gas (VGCG) models in non-flat universe on the basis of reviewing related contents for the NADE and VGCG models. Furthermore, we reconstruct the potential of the new agegraphic scalar field as well as the dynamics of the scalar field according to the evolution of the agegraphic dark energy. Finally, we generalize our study to the case of NADE with viscosity, which includes the case without viscosity (ν = 0) as a special case.

We study the bulk viscosity taking dust matter in the generalized teleparallel gravity. We consider different dark energy (DE) models in this scenario along with a time-dependent viscous model to construct the viscous equation of state (EoS) parameter for these DE models. We discuss the graphical representation of this parameter to investigate the viscosity effects on the accelerating expansion of the universe. It is mentioned here that the behavior of the universe depends upon the viscous coefficients showing the transition from decelerating to accelerating phase. It leads to the crossing of phantom divide line and becomes phantom dominated for specific ranges of these coefficients.

Bulk viscosity has been intrinsically existing in the observational cosmos evolution with various effects for different cosmological evolution stages endowed with complicated cosmic media. Normally in the idealized "standard cosmology", the physical viscosity effect is often negligent to some extent by assumptions, except for galaxies formation and evolution or like the astro-physics phenomena. Actually we have not fully understood the physical origin and effects of cosmic viscosity, including its functions for the universe evolution in reality. In this paper, we extend the concept of temperature-dependent viscosity from classical statistical physics to observational cosmology, especially we examine the cosmological effects with the possibility of existence for two kinds of viscosity forms, which are described by the Chapman's relation and Sutherland's formula, respectively. By considering that a modification of Standard Model with viscosity named as ΛCDM-V model is constructed, which is acceptable according to astrophysical observations. In addition to the enhancement to cosmic age value, the ΛCDM-V model possesses other two pleasing features: the prediction about the no-rip/singularity future and the mechanism of smooth transition from imperfect cosmological models to perfect ones.

In this paper, we report a study on the viscous extended holographic Ricci dark energy (EHRDE) model under the assumption of existence of bulk viscosity in the linear barotropic fluid and the EHRDE in the framework of standard Eckart theory of relativistic irreversible thermodynamics and it has been observed that the non-equilibrium bulk viscous pressure is significantly smaller than the local equilibrium pressure. We have studied the equation of state (EoS) parameter and observed that the EoS behaves like “quintom” and is consistent with the constraints set by observational data sets from SNLS3, BAO and Planck + WMAP9 + WiggleZ measurements in [S. Kumar and L. Xu, Phys. Lett. B737, 244 (2014)]. Analysis of statefinder parameters has shown the possibility of attainment of Lambda cold dark matter ($\mathrm{\Lambda }$CDM) phase under current model and at the same time it has been pointed out that the redshift z = 0, i.e. the current universe, the statefinder pair is different from that of $\mathrm{\Lambda }$CDM and the $\mathrm{\Lambda }$CDM can be attained in a later stage of the universe. An analysis of stability has shown that although the viscous EHRDE along with viscous barotropic is classically unstable in the present epoch, it can lead to a stable universe in very late stage. Considering an universe enveloped by event horizon, we have observed validity of generalized second law (GSL) of thermodynamics.

We study the evolution of viscous modified Chaplygin gas (MCG) interacting with f(R, T) gravity in flat FRW universe, where T is the trace of energy–momentum tensor. The field equations are formulated for a particular model f(R, T) = R + 2$\chi$T and constraints for the conservation of energy–momentum tensor are obtained. We investigate the behavior of total energy density, pressure and equation of state (EoS) parameter for emergent, intermediate as well as logamediate scenarios of the universe with two interacting models. It is found that the EoS parameter lies in the matter-dominated or quintessence era for all the three scenarios while the bulk viscosity enhances the expansion for the intermediate and logamediate scenarios.

Emergent universe model is presented in general theory of relativity with isotropic fluid in addition to viscosity. We obtain cosmological solutions that permit emergent universe scenario in the presence of bulk viscosity that are described by either Eckart theory or Truncated Israel Stewart (TIS) theory. The stability of the solutions are also studied. In this case, the emergent universe (EU) model is analyzed with observational data. In the presence of viscosity, one obtains emergent universe scenario, which however is not permitted in the absence of viscosity. The EU model is compatible with cosmological observations.

Causal cosmological evolutions in Randall Sundrum type II (RS) braneworld gravity with Gauss Bonnet coupling and dissipative effects are discussed here. Causal theory of dissipative effects are illustrated by Full Israel Stewart theory are implemented. We consider the numerical solutions of evolutions and analytic solutions as a special case for extremely non-linear field equation in Randall Sundrum type II braneworld gravity with Gauss Bonnet coupling. Cosmological models admitting Power law expansion, Exponential expansion and evolution in the vicinity of the stationary solution of the universe are investigated for Full Israel Stewart theory. Stability of equilibrium or fixed points related to the dynamics of evolution in Full Israel Stewart theory in Randall Sundrum type II braneworld gravity together with Gauss Bonnet coupling are disclosed here.

In this paper, we study the thermodynamical and mathematical consistencies for a non-singular early-time viscous cosmological model known as soft-Big Bang, which was previously found in [N. Cruz, E. González and J. Jovel, Phys. Rev. D 105, 024047 (2022)]. This model represents a flat homogeneous and isotropic universe filled with a dissipative radiation fluid and a cosmological constant $\mathrm{\Lambda }$, which is small but not negligible, in the framework of Eckart’s theory. In particular, we discuss the capability of the solution in the fulfillment of the three following conditions: (i) the near equilibrium condition, which is assumed in Eckart’s theory of non-perfect fluids, (ii) the mathematical stability of the solution under small perturbations, and (iii) the positiveness of the entropy production. We have found that this viscous model can describe the radiation domination era of the $\mathrm{\Lambda }$CDM model and, at the same time, fulfill the three conditions mentioned by the fulfillment of a single constraint on the bulk viscous coefficient ${\xi }_0$, finding also that this non-singular model has a positive energy density in the infinity past which is infinity hotter with a constant entropy.

We present a discussion of the effects induced by bulk viscosity on the very early Universe stability. The viscosity coefficient is assumed to be related to the energy density ρ via a power-law of the form ζ = ζ₀ρ^s (where ζ₀, s = const.) and the behavior of the density contrast in analyzed. In particular, we study both Einstein and hydrodynamic equations up to first and second order in time in the so-called quasi-isotropic collapsing picture near the cosmological singularity. As a result, we get a power-law solution existing only in correspondence to a restricted domain of ζ₀. The particular case of pure isotropic FRW dynamics is then analyzed and we show how the asymptotic approach to the initial singularity admits an unstable collapsing picture.

The quark viscosity in the quark gluon plasma is evaluated in Hard Thermal Loop (HTL) approximation. The different contributions to the viscosity arising from the various components of the quark spectral function are discussed.

Viscous properties are attributed to the dark sector of the Universe. They contribute to the accelerated expansion phase of the Universe and can alleviate existing tensions in the $\mathrm{\Lambda }$CDM model at small scales. We provide a short review of recent efforts on this topic. Different viscous models for the dark sector are analysed both from theoretical and observational point of view.

In this paper we study an impact of viscosity on DNA behaviour. We investigate a so-called big viscosity using extended Peyrard-Bishop model to describe nonlinear DNA dynamics.

Structural and dynamical properties of Pd, Ag pure liquid metals and especially Pd_xAg_1-x alloys are studied by the molecular dynamics simulation. The effects of temperature and concentration on the liquid properties of Pd_xAg_1-x are analyzed. Sutton–Chen (SC) and Quantum Sutton–Chen (Q–SC) many-body potentials are used as interatomic interactions. The calculated diffusion constants and viscosities are in good agreement with the available experimental data and theoretical calculations. The coefficients of Arrhenius equation are also presented to calculate the self-diffusion coefficient and shear viscosity of Pd–Ag alloys at the desired temperature and concentration. We have shown that Q–SC potential parameters are more reliable in determining physical properties of metals and their alloys studied in this work.

The interrelation between apparent viscosity in steady shear flow and complex viscosity in oscillatory shear flow for magnetorheological (MR) suspensions is investigated. Series of experiments have been conducted using a MR rheometer. An extended Rutgers–Delaware rule is proposed, in which an effective shear rate for oscillatory shear flow is defined as ωΔ_h. Here ωΔ_h is the shift factor dependent on strain amplitude (γ₀), which was found to be similar for different MR suspensions under different magnetic fields. At high strain amplitudes (γ₀≥100%), Δ_h≈γ₀, the Rutgers–Delaware rule is approximately obeyed. At low strain amplitudes (γ₀<100%), the curves of Δ_h fall between the line of the Cox–Merz rule and that of the Rutgers–Delaware rule. The curve of Δ_h at low strain amplitudes depends on the ingredients of the MR suspension. For samples with the same ingredients, a unified curve of Δ_h can be identified in a range of magnetic fields and/or for a range of volume fraction of magnetic particles.