Journal of Applied Physical Science International

Main task of this research paper is to investigate the optical properties (including dielectric function, refractive index, extinction coefficient, loss function, absorption coefficient, and conductivity) of transition metal diborides MB₂ (M = Ti, Nb, Zr) as a function of photon energy in [100] direction. Theoretical and experimental data are compared with each other for the better understanding of this research work.

We consider diffusion caused by a combined influence of the Hall effect and electric currents, and argue that such diffusion forms chemical inhomogeneities in plasma. The considered mechanism can be responsible for the formation of element spots in laboratory and astrophysical plasmas. Such current-driven diffusion can be accompanied by the propagation of a paticular type of waves which have not been considered earlier. In these waves, the impurity number density oscillates alone and their frequency is determined by the electric currents and sort of impurity ions. These compositional waves exist if the magnetic pressure in plasma is much greater than the gas pressure. Such waves lead to local variations of chemical composition in plasma and, hence, can manifest themself by variations of the emission in spectral lines.

We study the fluctuation-electromagnetic interaction and dynamics of a small spinning polarizable particle moving with a relativistic velocity in a vacuum background of arbitrary temperature. Using the standard formalism of the fluctuation electromagnetic theory, a complete set of equations describing the decelerating tangential force, the components of the torque and the intensity of nonthermal and thermal radiation is obtained along with equations describing the dynamics of translational and rotational motion, and the kinetics of heating. An interplay between various parameters is discussed. Numerical estimations for conducting particles were carried out using MATHCAD code. In the case of zero temperature of a particle and background radiation, the intensity of radiation is independent of the linear velocity, while the angular velocity orientation and the linear velocity value are independent of time. In the case of a finite background radiation temperature, the angular velocity vector tends to be oriented perpendicularly to the linear velocity vector. The particle temperature relaxes to a quasistationary value depending on the background radiation temperature, the linear and angular velocities, whereas the intensity of radiation depends on the background radiation temperature, the angular and linear velocities. The time of thermal relaxation is much less than the time of angular deceleration, while the latter time is much less than the time of linear deceleration.

Flow over a sphere placed above the surface is investigated in this work with a proper numerical technique. The Reynold’s number based on the sphere diameter is taken as Re ≈ 3×10⁴ i.e. the flow is fully turbulent. The standard k - ε and the standerd k - ω turbulence models are utilized to capture the flow behavior of the sphere. An unstructured mesh topology had been generated to mesh the sphere and its surrounding domain. Various fluid properties of the flow phenomena for the two turbulence models with proper contours and diagram were showed and discussed in details. The downstream complex flow phenomena are observed for this turbulent flow. The results and comparison between this two turbulence models showed better agreement for the present numerical technique.

In an automobile radiator, water and ethylene glycol (50-50) mixture is used as conventional coolants for many years. Thermal modeling of the existing radiator with conventional coolant property is performed and the heat transfer rate of the radiator is calculated. The heat transfer fluid has low thermal conductivity resulting in larger size radiators for a designed heat load. The present theoretical study focused to improve the heat transfer rate of the radiator by using nanofluid as an engine coolant. CuO-water and Al₂O₃-water nanofluids are used as engine coolant with five different volume concentrations in the range of 0.1% to 0.5%. It is observed that, about 6% of heat transfer enhancement could be achieved with the addition of 2% nanoparticle in the base fluid. From this study it was found out for the given heat load, the size of the radiator can be reduced by 25%, by replacing the water-ethylene glycol coolant with nanofluid based coolant. Also, the cost associated with the radiator is correspondingly reduced.