Presence Of Viscous Fluid Research Articles

Evolution of solitary hydroelastic strain waves in two coaxial cylindrical shells with the Schamel physical nonlinearity

The paper considers the formulation and solution of the hydroelasticity problem for studying wave processes in the system of two coaxial shells containing fluids in the annular gap between them and in the inner shell. We investigate the axisymmetric case for Kirchhoff–Lave type shells whose material obeys a physical law with a fractional exponent of the nonlinear term (Schamel nonlinearity). The dynamics of fluids in the shells is considered within the framework of the incompressible viscous Newtonian fluid model. The derivation of the Schamel nonlinear equations of shell dynamics makes it possible to develop a mathematical formulation of the problem, which includes the obtained equations, the dynamics equations of two shells, the fluid dynamics equations and the boundary conditions at the shell-fluid interfaces and at the flow symmetry axis. The asymptotic analysis of the problem is performed using perturbation techniques, and the system of two generalized Schamel equations is obtained. This system describes the evolution of nonlinear solitary hydroelastic strain waves in the coaxial shells filled with viscous fluids, taking into account the inertia of the fluid motion. In order to determine the fluid stress at the shell-fluid interfaces, we perform linearization of the fluid dynamics equations for fluids in the annular gap and in the inner shell. The linearized equations are solved by the iterative method. The inertial terms are excluded from the equations in the first iteration, while, in the second iteration, these are the values found in the first iteration. A numerical solution of the system of nonlinear evolution equations is obtained by applying a new difference scheme developed using the Gröbner basis technique. Computational experiments are performed to investigate the effect of fluid viscosity and the inertia of fluid motion in the shells on the wave process. In the absence of fluids in the inner shell, the results of calculations demonstrate that the strain waves in the shells during elastic interactions do not change their shape and amplitude, i.e., they are solitons. The presence of viscous fluid in the inner shell leads to attenuation of the wave process.

Bulk viscous fluid in extended symmetric teleparallel gravity

In this paper, we investigate the existence of bulk viscous FLRW cosmological models in a recently proposed extended symmetric teleparallel gravity or fQ,T gravity in which Q is the non-metricity and T is the trace of the energy–momentum tensor. We consider a simple coupling between matter and non-metricity, specifically, fQ,T=αQm+1+λT and fQ,T=αQ+λT where α, λ and m are free model parameters. The exact cosmological solutions are found by assuming the scale factor in the form of the hybrid expansion law. This type of relation generates a time-varying deceleration parameter with the transition of the Universe from the early decelerating phase to the present accelerating phase. In the presence of viscous fluid, we analyze some cosmological parameters of our cosmological model such as the energy density, bulk viscous pressure, bulk viscous coefficient, equation of state parameter, and energy conditions. Finally, we conclude our fQ,T cosmological models agree with the recent astronomical observations.

Impact of Homogeneous/Heterogeneous Reactions and Convective Conditions on Peristaltic Fluid Flow in a Symmetric Channel

Simultaneous impacts of homogeneous and heterogeneous reaction and Joule heating in magnetohydrodynamic (MHD) peristaltic flow of viscous fluid in a symmetric channel are analyzed in this investigation. Attention has been focused on designing and simulating a mathematical model for a viscous fluid in presence of viscous dissipation. Long wavelength approximation in wave frame analysis is implemented. Expressions for the stream function, axial pressure gradient, temperature, heat transfer coefficient and concentration are derived and discussed. In addition, the trapping phenomenon is analyzed. The effects of the physical quantities of concern are viewed with a special focus on homogeneous and heterogeneous reaction and convective conditions for the transfer of heat at the walls. It is observed that the pressure rise first increases and then decreases with an increase in amplitude ratio. Effects of Brinkman and Hartmann numbers on temperature are quite analogous and a temperature rise is observed, however, temperature decays for the increased value of Biot number. Moreover, fluid concentration decreases when the value of the homogeneous reaction parameter is increased.

Bulk viscous Bianchi type I cosmological model in Lyra geometry and in the general theory of relativity

In the framework of the gravitational theory based on Lyra geometry and the general theory of relativity, we study Bianchi type I cosmological model in the presence of viscous fluid. A discussion about the suitability of the Sen equations as field equations in Lyra geometry is given. A clear physical meaning for the time component of the displacement vector, introduced in the Sen field equations used in the framework of Lyra geometry, is given by identifying it as a part of the energy momentum tensor (viscosity term). Exact solution of the Einstein field equations is given by assuming the model has a constant deceleration parameter. Moreover, we study the effect of the viscosity term on the entropy of the universe. A formula for calculating the entropy in the presence of viscosity is given by a combination between the second law of thermodynamics and the energy momentum tensor in a conservative manner. We calculate and study the thermodynamic functions (Enthalpy, Gibbs energy and Helmholtz energy) of the universe in the presence of viscosity in Lyra geometry and in the general theory of relativity. The physical and geometrical properties of the obtained models are discussed.

Imaging the shear and secondary compression wave: Ultrafast ultrasound in saturated foams reveals porous dispersion

Wave propagation in porous materials is of relevance in many fields of acoustics such as geophysics, noise cancellation, and biomedical imaging. In contrast to classical elastic materials, poroelastic materials support three types of elastic waves and exhibit a distinctive dispersion in the presence of viscous fluids. In addition to the compression and shear wave, a secondary compression wave, often named Biot slow wave, exists. Both, the slow compression wave and the shear wave are highly attenuated. This poses crucial difficulties for experimental detection. We overcome this challenge by using high frame rate ultrasound imaging for wave tracking inside saturated, highly porous melamine foams. To our knowledge, we show the first experimental speed and attenuation measurements inside a soft porous materials. In particular, experimental detection of the slow compression wave is scarce, and no direct imaging inside a porous material has been reported. Both wavespeeds are governed by the weak frame of the foam and exhibit a strong dispersion due to the fluid viscosity. Our experiments have direct implications for medical imaging: Melamine foams exhibit a similar microstructure as lung tissue. Furthermore, other organs such as the liver can be modeled as a soft porous material.Wave propagation in porous materials is of relevance in many fields of acoustics such as geophysics, noise cancellation, and biomedical imaging. In contrast to classical elastic materials, poroelastic materials support three types of elastic waves and exhibit a distinctive dispersion in the presence of viscous fluids. In addition to the compression and shear wave, a secondary compression wave, often named Biot slow wave, exists. Both, the slow compression wave and the shear wave are highly attenuated. This poses crucial difficulties for experimental detection. We overcome this challenge by using high frame rate ultrasound imaging for wave tracking inside saturated, highly porous melamine foams. To our knowledge, we show the first experimental speed and attenuation measurements inside a soft porous materials. In particular, experimental detection of the slow compression wave is scarce, and no direct imaging inside a porous material has been reported. Both wavespeeds are governed by the weak frame of the fo...

Entropy Generation and Activation Energy Impact on Radiative Flow of Viscous Fluid in Presence of Binary Chemical Reaction

Abstract The main theme of this paper is to investigate entropy generation analysis for unsteady three-dimensional flow of viscous (Newtonian) fluid between two horizontal parallel plates. Lower plate is porous and stretching while upper plate squeezed downward. Further effects of nonlinear thermal radiation, viscous dissipation, heat source/sink and activation energy are accounted. Entropy generation rate calculated in terms of thermal radiation, fluid diffusion and fluid friction. Transformations procedure used lead to reduction of PDE’s into ordinary ones. Built-in-Shooting technique is used for the computational analysis. Impacts of different flow variables on temperature, velocity, concentration, volumetric entropy generation and Bejan number are discussed and presented through graphs. Temperature and concentration gradient are discussed numerically. It is examined from obtained results that velocity of liquid particle decays through larger estimation of squeezing parameter. It is also examined that temperature distribution enhances for higher estimation of radiative heat flux. Moreover temperature and concentration gradient increase for larger squeezing parameter.

Bianchi-I cosmology from causal thermodynamics

We investigate diagonal Bianchi-I spacetimes in the presence of viscous fluids by using the shear and the anisotropic pressure components as the basic variables, where the viscosity is driven by the (second-order) causal thermodynamics. A few exact solutions are presented, among which we mention the anisotropic versions of de Sitter/anti-de Sitter geometries as well as an asymptotically isotropic spacetime presenting an effectively constant cosmic acceleration without any cosmological constant. The qualitative analysis of the solutions for barotropic fluids with linear equations of state suggests that the behaviour is quite general.

Kaluza-Klein Bulk Viscous Cosmological Model with Time Dependent Gravitational Constant and Cosmological Constant

Cosmological models with time varying gravitational constant G and cosmological constant Λ in the presence of viscous fluid in Kaluza-Klein metric were investigated. The solutions to Einstein Field Equation were obtained for different types of G, with bulk coefficient ξ = ξ 0 ρ d (where ρ is density of the Universe, d is some constant) and lambda Λ = α H 2 + β R −2 where H and R are Hubble parameter and scale factor respectively. Two possible models are suggested, one where G is proportional to H and, the other where G is inversely proportional to H. While the former leads to a non-singular model, the latter results in an inflationary model. Both Cosmological models show that the Universe is accelerating; but at the early stage of the Universe the behaviour of both models is quite different,which has been studied through the variation of decelerating parameter q with time.

Heat and mass transfer in unsteady rotating fluid flow with binary chemical reaction and activation energy.

In this study, the Spectral Relaxation Method (SRM) is used to solve the coupled highly nonlinear system of partial differential equations due to an unsteady flow over a stretching surface in an incompressible rotating viscous fluid in presence of binary chemical reaction and Arrhenius activation energy. The velocity, temperature and concentration distributions as well as the skin-friction, heat and mass transfer coefficients have been obtained and discussed for various physical parametric values. The numerical results obtained by (SRM) are then presented graphically and discussed to highlight the physical implications of the simulations.

Some exact solutions of magnetized viscous model in string cosmology

In this paper, we study anisotropic Bianchi-V Universe with magnetic field and bulk viscous fluid in string cosmology. Exact solutions of the field equations are obtained by using the equation of state (EoS) for a cloud of strings, and a relationship between bulk viscous coefficient and scalar expansion. The bulk viscous coefficient is assumed to be inversely proportional to the expansion scalar. It is interesting to examine the effects of magnetized bulk viscous string model in early and late stages of evolution of the Universe. This paper presents different string models like geometrical (Nambu string), Takabayasi (p-string) and Reddy string models by taking certain physical conditions. We discuss the nature of classical potential for viscous fluid with and without magnetic field. The presence of bulk viscosity stops the Universe from becoming empty in its future evolution. It is observed that the Universe expands with decelerated rate in the presence of viscous fluid with magnetic field whereas, it expands with marginal inflation in the presence of viscous fluid without magnetic field. The other physical and geometrical aspects of each string model are discussed in detail.

Intrapleural Fibrinolytic Therapy in a Neonate

Pleural effusions are common complications of pediatric bacterial pneumonias. Failure to control the pleural effusions may lead to progressive disease and can result in complicated parapneumonic effusions. The natural history of a complicated parapneumonic effusion is to develop a single loculus or multiple loculations and then progress to an empyema cavity in untreated or inadequately treated patients. Simple chest tube drainage is often inadequate in complicated parapneumonic effusions, due to the presence of viscous fluid with fibrinous debris clogging the tube ormultiple loculations in the pleural space.

Bianchi Type-III Bulk Viscous and Barotropic Perfect Fluid Cosmological Models in Lyra’s Geometry

We have investigated Bianchi type III bulk viscous and barotropic perfect fluid cosmological models in the frame work of Lyra’s geometry. To get deterministic models of universe, we have assumed the three conditions: (i) shear scalar (σ) is proportional to the expansion (θ). This leads to B=Cn, where B and C are metric potentials. (ii) In presence of viscous fluid, the coefficient of viscosity of dissipative fluid is a power function of mass density ξ=ξ0ρm, where ξ0 and m are constant and (iii) in absence of viscosity, a proportionality relation between pressure and energy density of barotropic perfect fluid p=αρ, where α is a proportionality constant. In all the cases, we observed that the displacement vector β is large at beginning of the universe and reduces fast during its evolution so that its nature coincide with the behavior of cosmological constant Λ.

Bulk viscous cosmological models of universe with variable deceleration parameter in Lyra’s Manifold

FRW models of universe in the presence of viscous fluid are investigated in the cosmological theory based on Lyra’s Manifold. By considering the deceleration parameter to be a variable and the viscosity coefficient of bulk viscous fluid to be a constant, exacts solutions have been obtained from which three forms of model of the universe are derived. The physical properties of the models are also investigated.

Anisotropic cosmological models with spinor and scalar fields and viscous fluid in presence of a Λ term: Qualitative solutions

The study of a self-consistent system of interacting spinor and scalar fields within the scope of a Bianchi type I (BI) gravitational field in the presence of a viscous fluid and Λ term has been carried out. The system of equations defining the evolution of the volume scale of BI universe, energy density, and corresponding Hubble constant has been derived. The system in question has been thoroughly studied qualitatively. Corresponding solutions are graphically illustrated. The system in question is also studied from the view point of blow up. It has been shown that the blow up takes place only in the presence of viscosity.

Bianchi type VI0 magnetized bulk viscous massive string cosmological model in General Relativity

The paper consists of some exact solutions for a homogeneous Bianchi type VI0 universe. The material distribution is taken to be a magnetized bulk viscous fluid in presence of massive cosmological string. We assume that current is flowing along x-direction. Therefore, the magnetic field is in yz-plane. For deterministic model of the universe, we assume that shear (σ) is proportional to the expansion (θ) and ζ θ=constant=ξ where ζ the coefficient of bulk viscosity and θ the expansion in the model. The physical and kinematical parameters of the models thus formed are discussed.

Nonlinear spinor field in Bianchi type-I Universe filled with viscous fluid: numerical solutions

We consider a system of nonlinear spinor and a Bianchi type I gravitational fields in presence of viscous fluid. The nonlinear term in the spinor field Lagrangian is chosen to be $\lambda F$, with $\lambda$ being a self-coupling constant and $F$ being a function of the invariants $I$ an $J$ constructed from bilinear spinor forms $S$ and $P$. Self-consistent solutions to the spinor and BI gravitational field equations are obtained in terms of $\tau$, where $\tau$ is the volume scale of BI universe. System of equations for $\tau$ and $\ve$, where $\ve$ is the energy of the viscous fluid, is deduced. This system is solved numerically for some special cases.

Cosmological viscous fluid models in the presence of electromagnetic field and zero-mass scalar field

The problem of electromagnetic field interacting with viscous fluid without and with zero-mass scalar field has been studied. It has been shown that electromagnetic field cannot interact with viscous fluid for spherically-symmetric Robertson-Walker metric. Exact solutions corresponding to the problem of electromagnetic field interactions in presence of viscous fluid and zero-mass scalar field have been obtained subject to various physical conditions. It presents a scope for the study of imperfect fluid FRW models showing the existence of the electromagnetic field due to the presence of zero-mass scalar field.

Injection Well Logging Using Viscous EOR Fluids

Summary A new tool has been developed that overcomes problems associated with logging injection wells in the presence of viscous fluids. The tool was evaluated in the laboratory and the field in water and polymer injection wells. Results indicate that the tool provides better information than conventional equipment. Special attention to log interpretation is required in zones where the flow pattern changes from turbulent to transition flow. A method is suggested to improve log interpretation that considers changes in flow regime.