- Dettagli della rivista
- Formato
- Rivista
- eISSN
- 2353-9003
- Pubblicato per la prima volta
- 19 Apr 2013
- Periodo di pubblicazione
- 4 volte all'anno
- Lingue
- Inglese

#### Cerca

Accesso libero

#### Specification of the process of chloride extraction from reinforced concrete based on the inverse task of the diffusion equation

Pagine: 261 - 271

#### Astratto

When the structure of reinforcement is in danger of chloride corrosion it is possible to prevent this disadvantageous phenomenon through exposing the cover to the influence of an electric field. The forces of an electric field considerably reduce chloride ions in pore liquid in concrete, which helps to rebuild a passive layer on the surface of the reinforcement and stops corrosion. The process of removing chlorides can be described with multi-component diffusion equations. However, an essential parameter of these equations, the diffusion coefficient, can be determined on the basis of an inverse task. Since the solution was achieved for one-dimension flow, the method applied can be confirmed by experimental results and the material parameters of the process can be determined theoretically. Some examples of numerical calculations of the effective electro-diffusion coefficient of chloride ions confirmed the usefulness of the theoretical solution for generalizing experimental results. Moreover, the calculation process of the numerical example provides some practical clues for future experimental research, which could be carried out in close connection with the theoretical solution.

#### Parole chiave

- corrosion
- diffusion
- inverse task
- removing chlorides
- extraction

Accesso libero

#### Ferrofluid flow due to a rotating disk in the presence of a non-uniform magnetic field

Pagine: 273 - 283

#### Astratto

The flow of a ferrofluid due to a rotating disk in the presence of a non-uniform magnetic field in the axial direction is studied through mathematical modeling of the problem. Contour and surface plots in the presence of

#### Parole chiave

- magnetization force
- ferrofluid
- rotating disk
- magnetic field

Accesso libero

#### Propagation of plane waves in a rotating transversely isotropic two temperature generalized thermoelastic solid half-space with voids

Pagine: 285 - 301

#### Astratto

The paper is concerned with the propagation of plane waves in a transversely isotropic two temperature generalized thermoelastic solid half-space with voids and rotation. The governing equations are modified in the context of Lord and Shulman theory of generalized thermoelasticity and solved to show the existence of four plane waves in the

#### Parole chiave

- anisotropy
- generalized thermoelasticity
- voids
- plane waves
- reflection
- reflection coefficients

Accesso libero

#### Scattering of interface wave by bottom undulations in the presence of thin submerged vertical wall with a gap

Pagine: 303 - 322

#### Astratto

In this paper, the problem of interface wave scattering by bottom undulations in the presence of a thin submerged vertical wall with a gap is investigated. The thin vertical wall with a gap is submerged in a lower fluid of finite depth with bottom undulations and the upper fluid is of infinite height separated by a common interface. In the method of solution, we use a simplified perturbation analysis and suitable applications of Green’s integral theorem in the two fluid regions produce first-order reflection and transmission coefficients in terms of integrals involving the shape function describing the bottom undulations and solution of the scattering problem involving a submerged vertical wall present in the lower fluid of uniform finite depth. For sinusoidal bottom undulations, the first-order transmission coefficient vanishes identically. The corresponding first-order reflection coefficient is computed numerically by solving the zero-order reflection coefficient and a suitable application of multi-term Galerkin approximations. The numerical results of the zero-order and first-order reflection coefficients are depicted graphically against the wave number in a number of figures. An oscillatory nature is observed of first-order reflection coefficient due to multiple interactions of the incident wave with bottom undulations, the edges of the submerged wall and the interface. The first-order reflection coefficient has a peak value for some particular value of the ratio of the incident wavelength and the bottom wavelength. The presence of the upper fluid has some significant effect on the reflection coefficients.

#### Parole chiave

- submerged vertical wall
- perturbation analysis
- interface wave scattering
- sinusoidal bottom
- Galerkin approximations
- zero-order reflection coefficient
- first-order reflection coefficient

Accesso libero

#### Magneto-polar fluid flow through a porous medium of variable permeability in slip flow regime

Pagine: 323 - 339

#### Astratto

A theoretical study is carried out to obtain an analytical solution of free convective heat transfer for the flow of a polar fluid through a porous medium with variable permeability bounded by a semi-infinite vertical plate in a slip flow regime. A uniform magnetic field acts perpendicular to the porous surface. The free stream velocity follows an exponentially decreasing small perturbation law. Using the approximate method the expressions for the velocity, microrotation, and temperature are obtained. Further, the results of the skin friction coefficient, the couple stress coefficient and the rate of heat transfer at the wall are presented with various values of fluid properties and flow conditions.

#### Parole chiave

- polar fluid
- MHD
- permeability
- slip-flow
- heat transfer

Accesso libero

#### Effect of slip condition on vertical channel flow in the presence of radiation

Pagine: 341 - 358

#### Astratto

An analysis is made on the three dimensional flow of a viscous incompressible fluid through a vertical channel in the presence of radiation in slip flow regime. The right plate is subjected to an uniform injection and the left plate to a periodic suction velocity distribution. The velocity and temperature fields have been derived using the perturbation technique. It is found that the velocity decreases with the increase of the slip parameter. It is also found that the velocity decreases with the increase of the radiation parameter but near the right plate it increases. For cooling of the plate, the velocity increases with the increase of the Grashoff number and decreases near the right plate but the reverse effect is observed for heating the plate.

#### Parole chiave

- three-dimensional
- injection
- suction
- buoyancy
- transpiration cooling
- free convection

Accesso libero

#### Three dimensional flow and mass transfer analysis of a second grade fluid in a porous channel with a lower stretching wall

Pagine: 359 - 376

#### Astratto

This investigation analyses a three dimensional flow and mass transfer of a second grade fluid over a porous stretching wall in the presence of suction or injection. The equations governing the flow are attained in terms of partial differential equations. A similarity transformation has been utilized for the transformation of partial differential equations into the ordinary differential equations. The solutions of the nonlinear systems are given by the homotopy analysis method (HAM). A comparative study with the previous results of a viscous fluid has been made. The convergence of the series solution has also been considered explicitly. The influence of admissible parameters on the flows is delineated through graphs and appropriate results are presented. In addition, it is found that instantaneous suction and injection reduce viscous drag on the stretching sheet. It is also shown that suction or injection of a fluid through the surface is an example of mass transfer and it can change the flow field.

#### Parole chiave

- second grade fluid
- stretching wall
- suction
- injection

Accesso libero

#### Thermal analysis of a fully wet porous radial fin with natural convection and radiation using the spectral collocation method

Pagine: 377 - 392

#### Astratto

Heat transfer with natural convection and radiation effect on a fully wet porous radial fin is considered. The radial velocity of the buoyancy driven flow at any radial location is obtained by applying Darcy’s law. The obtained non-dimensionalized ordinary differential equation involving three highly nonlinear terms is solved numerically with the spectral collocation method. In this approach, the dimensionless temperature is approximated by Chebyshev polynomials and discretized by Chebyshev-Gausse-Lobatto collocation points. A particular algorithm is used to reduce the nonlinearity of the conservation of energy equation. The present analysis characterizes the effect of ambient temperature in different ways and it provides a better picture regarding the effect of ambient temperature on the thermal performance of the fin. The profiles for temperature distributions and dimensionless base heat flow are obtained for different parameters which influence the heat transfer rate.

#### Parole chiave

- wet porous radial fin
- natural convection
- radiation
- thermal analysis
- spectral collocation method

Accesso libero

#### Three-dimensional MHD boundary layer flow due to an axisymmetric shrinking sheet with radiation, viscous dissipation and heat source/sink

Pagine: 393 - 406

#### Astratto

An analysis is made to study a three dimensional MHD boundary layer flow and heat transfer due to a porous axisymmetric shrinking sheet. The governing partial differential equations of momentum and energy are transformed into self similar non-linear ordinary differential equations by using the suitable similarity transformations. These equations are, then solved by using the variational finite element method. The flow phenomena is characterised by the magnetic parameter _{p}

#### Parole chiave

- axisymmetric shrinking sheet
- dual solution
- radiation
- viscous dissipation
- FEM

Accesso libero

#### Convective heat transfer in a micropolar fluid over an unsteady stretching surface

Pagine: 407 - 422

#### Astratto

An unsteady boundary layer free convective flow and heat transfer of a viscous incompressible, microploar fluid over a vertical stretching sheet is investigated. The stretching velocity is assumed to vary linearly with the distance along the sheet. Two equal and opposite forces are impulsively applied along the

#### Parole chiave

- unsteady flow
- microrotation
- heat transfer
- skin friction
- Nusselt number
- Keller-box method

Accesso libero

#### Unsteady two-layered fluid flow of conducting fluids in a channel between parallel porous plates under transverse magnetic field in a rotating system

Pagine: 423 - 446

#### Astratto

An unsteady MHD two-layered fluid flow of electrically conducting fluids in a horizontal channel bounded by two parallel porous plates under the influence of a transversely applied uniform strong magnetic field in a rotating system is analyzed. The flow is driven by a common constant pressure gradient in a channel bounded by two parallel porous plates, one being stationary and the other oscillatory. The two fluids are assumed to be incompressible, electrically conducting with different viscosities and electrical conductivities. The governing partial differential equations are reduced to the linear ordinary differential equations using two-term series. The resulting equations are solved analytically to obtain exact solutions for the velocity distributions (primary and secondary) in the two regions respectively, by assuming their solutions as a combination of both the steady state and time dependent components of the solutions. Numerical values of the velocity distributions are computed for different sets of values of the governing parameters involved in the study and their corresponding profiles are also plotted. The details of the flow characteristics and their dependence on the governing parameters involved, such as the Hartmann number, Taylor number, porous parameter, ratio of the viscosities, electrical conductivities and heights are discussed. Also an observation is made how the velocity distributions vary with the rotating hydromagnetic interaction in the case of steady and unsteady flow motions. The primary velocity distributions in the two regions are seen to decrease with an increase in the Taylor number, but an increase in the Taylor number causes a rise in secondary velocity distributions. It is found that an increase in the porous parameter decreases both the primary and secondary velocity distributions in the two regions.

#### Parole chiave

- magnetohydrodynamics
- two-layered fluids/immiscible fluids
- rotating fluids
- oscillating flow
- unsteady flow
- porous plates

Accesso libero

#### Propagation of SH waves in an regular non homogeneous monoclinic crustal layer lying over a non-homogeneous semi-infinite medium

Pagine: 447 - 459

#### Astratto

The present paper discusses the dispersion equation for SH waves in a non-homogeneous monoclinic layer over a semi infinite isotropic medium. The wave velocity equation has been obtained. In the isotropic case, when non-homogeneity is absent, the dispersion equation reduces to the standard SH wave equation. The dispersion curves are depicted by means of graphs for different values of non-homogeneity parameters for the layer and semi-infinite medium.

#### Parole chiave

- SH waves
- monoclinic
- non homogeneity
- differential equations

Accesso libero

#### Closed system of coupling effects in generalized thermo-elastoplasticity

Pagine: 461 - 483

#### Astratto

In this paper, the field equations of the generalized coupled thermoplasticity theory are derived using the postulates of classical thermodynamics of irreversible processses. Using the Legendre transformations two new thermodynamics potentials

#### Parole chiave

- thermodynamic potentials
- couplings effects
- stresses
- deformations
- temperature
- entropy
- enthalpy
- constitutive and rate equations
- yield surface
- plastic potential

Accesso libero

#### Probabilistic buckling analysis of the beam steel structures subjected to fire by the stochastic finite element method

Pagine: 485 - 510

#### Astratto

The main purpose is to present the stochastic perturbation-based Finite Element Method analysis of the stability in the issues related to the influence of high temperature resulting from a fire directly connected with the reliability analysis of such structures. The thin-walled beam structures with constant cross-sectional thickness are uploaded with typical constant loads, variable loads and, additionally, a temperature increase and we look for the first critical value equivalent to the global stability loss. Such an analysis is carried out in the probabilistic context to determine as precisely as possible the safety margins according to the civil engineering Eurocode statements. To achieve this goal we employ the additional design-oriented Finite Element Method program and computer algebra system to get the analytical polynomial functions relating the critical pressure (or force) and several random design parameters; all the models are state-dependent as we consider an additional reduction of the strength parameters due to the temperature increase. The first four probabilistic moments of the critical forces are computed assuming that the input random parameters have all Gaussian probability functions truncated to the positive values only. Finally, the reliability index is calculated according to the First Order Reliability Method (FORM) by an application of the limit function as a difference in-between critical pressure and maximum compression stress determined in the given structures to verify their durability according to the demands of EU engineering designing codes related to the fire situation.

#### Parole chiave

- stability analysis
- linearized buckling
- fire simulation
- stochastic perturbation method
- stochastic finite element method
- response function method
- reliability analysis

Accesso libero

#### Industrial noise level study in a wheat processing factory in ilorin, nigeria

Pagine: 511 - 523

#### Astratto

An industrial process such as wheat processing generates significant noise which can cause adverse effects on workers and the general public. This study assessed the noise level at a wheat processing mill in Ilorin, Nigeria. A portable digital sound level meter HD600 manufactured by Extech Inc., USA was used to determine the noise level around various machines, sections and offices in the factory at pre-determined distances. Subjective assessment was also mode using a World Health Organization (WHO) standard questionnaire to obtain information regarding noise ratings, effect of noise on personnel and noise preventive measures. The result of the study shows that the highest noise of

#### Parole chiave

- wheat processing
- noise level
- digital sound meter
- questionnaire
- hearing protector