Rayleigh-Bѐnard Convection in a Second-Order Fluid with Maxwell-Cattaneo Law

The objective of the paper is to study the Rayleigh-Bѐnard convection in second order fluid by replacing the classical Fourier heat law by non-classical Maxwell-Cattaneo law using Galerkin technique. The eigen value of the problem is obtained using the general boundary conditions on velocity and third type of boundary conditions on temperature. A linear stability analysis is performed. The influence of various parameters on the onset of convection has been analyzed. The classical Fourier flux law over predicts the critical Rayleigh number compared to that predicted by the non-classical law. The present non-classical Maxwell-Cattaneo heat flux law involves a wave type heat transport (SECOND SOUND) and does not suffer from the physically unacceptable drawback of infinite heat propagation speed. It is found that the results are noteworthy at short times and the critical eigen values are less than the classical ones. Over stability is the preferred mode of convection.

Research on the Thermal Property of Lightweight-Aggregate-Concrete Hollow-Block Wall

The Theoretical calculation and the finite element method (FEM) are used for studying the thermal property of hollow-block and hollow-masonry. The method of appendix in the standard for Thermal Design of Civil Buildings is adopted to calculate the thermal resistance and the average thermal conductivity of hollow-block and hollow-masonry. ANSYS is used for simulating temperature distribution and heat flux law under connective loads. The conduction and convection phenomena are taking into account in this study for four different values of the mortar conductivity and four different values for the bricks. The thermal resistance and the average thermal conductivity of hollow-block and hollow-masonry is the key factor for reference.

Rayleigh-Benard Convection With Second-Sound in a Viscoelastic Fluid-Filled High-Porosity Medium

The linear stability of the Rayleigh-Benard situation in a viscoelastic fluid occupying a high-porosity medium is investigated. The viscoelastic correction to Brinkman momentum equation is effected by considering the modified form of Jeffrey constitutive equation. Further, the non-classical Maxwell-Cattaneo heat flux has been used in place of the classical Fourier heat flux law. The results of the study reveal that the non-classical theory predicts finite speeds of heat propagation. The eigen value is obtained for free-free, isothermal boundary combinations and it has been observed that the critical Rayleigh number is less than the corresponding value of the problem governed by the classical Fourier law. The study finds application in progressive solidification of polymeric melts and solutions, and also in the manufacture of composite materials.