Some Inhomogeneous Magnetized Viscous Fluid Cosmological Models with Varying Λ\Lambda

Some cylindrically symmetric inhomogeneous viscous fluid cosmological models with electro-magnetic field are obtained. To get a solution a supplementary condition between metric potentials is used. The viscosity coefficient of bulk viscous fluid is assumed to be a power function of mass density. Without assumin g any {\it ad hoc} law, we obtain a cosmological constant as a decreasing function of time. The behaviour of the electro-magnetic field tensor together with some p hysical aspects of the model are also discussed.Comment: 17 pages, 1 figur

H-Theorem and Boundary Conditions for Two-Temperature Model: Application to Wave Propagation and Heat Transfer in Polyatomic Gases

Polyatomic gases find numerous applications across various scientific and technological fields, necessitating a quantitative understanding of their behavior in non-equilibrium conditions. In this study, we investigate the behavior of rarefied polyatomic gases, particularly focusing on heat transfer and sound propagation phenomena. By utilizing a two-temperature model, we establish constitutive equations for internal and translational heat fluxes based on the second law of thermodynamics. A novel reduced two-temperature model is proposed, which accurately describes the system's behavior while reducing computational complexity. Additionally, we develop phenomenological boundary conditions adhering to the second law, enabling the simulation of gas-surface interactions. The phenomenological coefficients in the constitutive equations and boundary conditions are determined by comparison with relevant literature. Our computational analysis includes conductive heat transfer between parallel plates, examination of sound wave behavior, and exploration of spontaneous Rayleigh-Brillouin scattering. The results provide valuable insights into the dynamics of polyatomic gases, contributing to various technological applications involving heat transfer and sound propagation

Bulk Viscous Cosmological Models in Barber's Second Self Creation Theory

Barber's second self creation theory with bulk viscous fluid source for an LRS Bianchi type-I metric is considered by using deceleration parameter to be constant where the metric potentials are taken as function of $x$ and $t$. The coefficient of bulk viscosity is assumed to be a power function of the mass density. Some physical and geometrical features of the models are discussedComment: latex, 10 pages, submitted in Int. J. Mod. Phys.

Boundary Layer Simulation using Wind Tunnel

For understanding the effect of vertical strips (varying configuration viz. c/c spacing and height) placed on the upstream of the surface under taken for studies on the growth of boundary layer, the experiments were carried in the laboratory using Wind tunnel. The variables include vertical strips of heights 20 cm, 30 cm and 40 cm with fixed central spacing of 8 cm c/c. and then 30 cm strips at varying central spacing at 6.5 cm and 14 cm c/c. The wall clearance in each case was kept 2 cm from both sides. The growth of boundary layer was found to be significantly affected on strips configuration. The boundary layer thickness increases with increase in height of the vertical in the range of the experiment. Also, the boundary layer thickness has been found to decrease with increase in c/c spacing of the strips. In the different section of wind tunnel reading of Boundary layer were taken with main stream velocity (U) which varies 10 to 12 m/s. With the concept of 99% (U) velocity profile is plotted at different location of working section length and the corresponding height is measured for the determination of Boundary layer. The velocity of fluid increases from zero velocity on the stationary boundary to the free stream velocity of the fluid in the direction normal to the Boundary. This variation in velocity normally takes place in the vicinity of solid Boundary, and this narrow region is termed as Boundary layer. So our main aim is to enhance the Boundary layer thickness which is achieved by using many passive devices like spire, cube as roughness elements and vertical strips of different sizes. My experiment is based on use of different size of vertical strips. Basically two things occur due to use of strips, one is it allows the formation of Vortex and consequent turbulence and second is it allows the air flow preferably on the upper part of the tunnel (main stream velocity)