Mohamed I. A. Othman

Bio: Mohamed I. A. Othman is an academic researcher from Zagazig University. The author has contributed to research in topics: Thermoelastic damping & Isotropy. The author has an hindex of 36, co-authored 239 publications receiving 4154 citations. Previous affiliations of Mohamed I. A. Othman include Shaqra University & Taif University.

Reflection of plane waves from an elastic solid half-space under hydrostatic initial stress without energy dissipation

Abstract: In this paper, the basic governing equations for isotropic and homogeneous generalized thermoelastic half-space under hydrostatic initial stress are formulated in the context of the Green and Naghdi theory of types II and III These governing equations are solved analytically to obtain the dimensional velocities in an xy-plane It is shown that there exist three plane waves, namely a thermal wave, a P-wave and an SV-wave The reflection from an insulated and isothermal stress-free surface is studied to obtain the reflection amplitude ratios of the reflected waves for the incidence of P- and SV-waves Numerical computations are carried out and comparisons made with the results predicted in the presence and absence of hydrostatic initial stress Also the effect of the thermoelastic coupling parameter and the thermal condition on amplitude ratios are shown graphically

Effect of thermal loading due to laser pulse on thermoelastic porous medium under G-N theory

Abstract: The aim of this paper is to study the wave propagation of generalized thermoelastic medium with voids under the effect of thermal loading due to laser pulse with energy dissipation. The material is a homogeneous isotropic elastic half-space and heated by a non-Gaussian laser beam with the pulse duration of 0.2 ps. A normal mode method is proposed to analyse the problem and obtain numerical solutions for the displacement components, stresses, temperature distribution and the change in the volume fraction field. The results of the physical quantities have been illustrated graphically by comparison between both types II and III of Green-Naghdi theory for two values of time, as well as with and without void parameters.

The effect of rotation on generalized micropolar thermoelasticity for a half-space under five theories

Abstract: A model of the equations of a two-dimensional problem in a micropolar thermoelastic medium for a half-space whose surface is free and subjected to an instantaneous thermal point source is studied. The entire elastic medium is rotating with a uniform angular velocity. The formulation is applied under five theories of the generalized thermoelasticity: Lord–Shulman with one relaxation time, Green–Lindsay with two relaxation times, Green–Naghdi theory (of type II) without energy dissipation and Chandrasekharaiah–Tzou theory with dual-phase-lag, as well as the coupled theory. The normal mode analysis is used to obtain the exact expressions for the considered variables. The distributions of the considered variables are illustrated graphically. Comparisons are made with the results predicted by the five theories in the presence and absence of rotation.

Effect of rotation on plane waves in generalized thermo-elasticity with two relaxation times

Abstract: The model of generalized thermo-elastic plane waves under the effect of rotation is studied using the theory of thermo-elasticity recently proposed by Green and Lindsay. The normal mode analysis is used to obtain the exact expressions for the temperature distribution, the displacement component and thermal stress. The resulting formulation is applied to two different concrete problems. The first deals with a thick plate subjected to a time-dependent heat source on each face. The second concerns the case of a heated punch moving across the surface of a semi-infinite thermo-elastic half-space subject to appropriate boundary conditions. Numerical results are given and illustrated graphically for each problem. Comparisons are made with the results predicted by the coupled theory and with the theory of generalized thermo-elasticity with two relaxation times in the absence of rotation.

A novel model of plane waves of two-temperature fiber-reinforced thermoelastic medium under the effect of gravity with three-phase-lag model

Abstract: In the present paper, the three-phase-lag (3PHL) model, Green-Naghdi theory without energy dissipation (G-N II) and Green-Naghdi theory with energy dissipation (G-N III) are used to study the influence of the gravity field on a two-temperature fiber-reinforced thermoelastic medium.,The analytical expressions for the displacement components, the force stresses, the thermodynamic temperature and the conductive temperature are obtained in the physical domain by using normal mode analysis.,The variations of the considered variables with the horizontal distance are illustrated graphically. Some comparisons of the thermo-physical quantities are shown in the figures to study the effect of the gravity, the two-temperature parameter and the reinforcement. Also, the effect of time on the physical fields is observed.,To the best of the author’s knowledge, this model is a novel model of plane waves of two-temperature fiber-reinforced thermoelastic medium, and gravity plays an important role in the wave propagation of the field quantities. It explains that there are significant differences in the field quantities under the G-N II theory, the G-N III theory and the 3PHL model because of the phase-lag of temperature gradient and the phase-lag of heat flux.

Effect of thermal radiation on magnetohydrodynamics nanofluid flow and heat transfer by means of two phase model

Abstract: In this study, effect of thermal radiation on magnetohydrodynamics nanofluid flow between two horizontal rotating plates is studied. The significant effects of Brownian motion and thermophoresis have been included in the model of nanofluid. By using the appropriate transformation for the velocity, temperature and concentration, the basic equations governing the flow, heat and mass transfer are reduced to a set of ordinary differential equations. These equations, subjected to the associated boundary conditions are solved numerically using the fourth-order Runge–Kutta method. The effects of Reynolds number, magnetic parameter, rotation parameter, Schmidt number, thermophoretic parameter, Brownian parameter and radiation parameter on heat and mass characteristics are examined. Results show that Nusselt number has direct relationship with radiation parameter and Reynolds number while it has reverse relationship with other active parameters. It can also be found that concentration boundary layer thickness decreases with the increase of radiation parameter.

About heat waves

Abstract: In 1982, the Belgian Pilots' Guild raised the question of what effect exposure to radar radiation--for example, that encountered in passing a pilot launch's radar--might have on the human body. Recapitulating investigations of this question, this article states that in 25 years of experience with radar, there have been no known incidents of pilots being affected by radar waves. In the future, however, involvement by some pilots with Vessel Traffic Service shore-based radar could affect pilots somewhat differently from limited exposure to pilot launch radar. Pilots who find themselves in new working conditions close to an emitting source should exercise care all times.

The Diffusion of Solids

Abstract: IN view of the interest attaching to the vaporisation and diffusion of solids, the following observations may be worthy of record.

Three dimensional mesoscopic simulation of magnetic field effect on natural convection of nanofluid

Abstract: In this paper magnetohydrodynamics nanofluid hydrothermal treatment in a cubic cavity heated from below is presented. The mathematical model consists of continuity and the momentum equations, while a new model is proposed to see the effects Brownian motion on the effective viscosity and thermal conductivity of nanofluid. The Lattice Boltzmann method is utilized to simulate three dimensional problems. The Koo–Kleinstreuer–Li correlation is also taken into account. Numerical calculation is made for different values of Hartmann number, nanoparticle volume fraction and Rayleigh number. The results are presented graphically in terms of streamlines, isotherms and isokinetic energy as well as Nusselt number. It is observed that the applying magnetic field results in a force opposite to the flow direction that leads to drag the flow and then reduces the convection currents by reducing the velocities. Also it can be concluded that Nusselt number is an increasing function of Rayleigh number and nanofluid volume fraction while it is a decreasing function of Hartmann number.