Immersed boundary—thermal lattice Boltzmann method for the moving simulation of non-isothermal elliptical particles

Journal of Thermal Analysis and Calorimetry - The study is concerned with the understanding of elliptical particles’ transport behavior coupled with heat transfer effects. A combination of...     

Investigation of stresses and normal stress differences behavior on symmetric and asymmetric polymeric fluid flow through planar gradual expansions

A numerical study of stress distribution of polymeric viscoelastic fluids passing through planar gradual expansion channels is conducted. To model the viscoelastic behavior in geometries with 1:3 expansion ratios, the exponential form of Phan-Thien Tanner model is employed as the constitutive equation. The PISO algorithm is used to solve the flow field distribution. Three different expansion angles of 30°, 45° and 60° are considered to probe the effects of the gradual expansion and its effect on the stress field distribution. The main purpose of the current study is to analysis the combined effects of the rheological properties and inertia on the normal stress distribution. To achieve this aim, different expansion angles and different ranges of Weissenberg and Reynolds numbers are studied.     

An exact analytical solution for creeping Dean flow of Bingham plastics through curved rectangular ducts

In this paper, an exact analytical solution for creeping flow of Bingham plastic fluid passing through curved rectangular ducts is presented for the first time. The closed form of axial velocity distribution, flow resistance ratio, and wall shear stress are derived using bounded Fourier transformation. An extensive investigation on mutual effects of Hedstrom number, curvature ratio, and aspect ratio is conducted. The results indicate that a drag reduction is caused in the flow field by increasing the Hedstrom number. It is shown that unlike the Newtonian creeping Dean flow, the critical aspect ratio (an aspect ratio in which the flow resistance ratio is independent from curvature ratio) does not exist at large enough Hedstrom numbers. Analytical solution also indicated that as Hedstrom number is increased, the value of Poiseuille number is enhanced, and unlike the Newtonian flows, the value of Poiseuille number is not zero at edges of cross section.     

Numerical simulation of inertial flow of heated and cooled viscoelastic fluids inside a planar sudden expansion channel: investigation of stresses effects on the total dissipation

In this paper, the inertial and non-isothermal flow of viscoelastic fluids in a planar channel with 1:3 sudden expansion has been simulated for Brinkman numbers in the range \( - \,20 \le Br \le 20 \). The mass, momentum and energy conservation equations with the non-linear form of Phan-Thien–Tanner constitutive equation are used to describe the behavior of heated and cooled viscoelastic fluids flow. The properties of fluid are assumed temperature-dependent and the viscous dissipation terms are considered in the energy equation. The object of the current paper is to investigate the stresses and their effects on heat generation via the viscous dissipation terms in the energy equation for inertial flow of heated and cooled viscoelastic fluids. Therefore, plots of streamlines, isothermal lines, normal stress (\( \tau_{xx} \)), normal-transverse stress (\( \tau_{yy} \)) and shear stress (\( \tau_{xy} \)), total dissipation, temperature and local Nusselt numbers have been drawn and examined in the channel expansion. The results show that for the asymmetric flow of heated and cooled viscoelastic fluids, the maximum values of total dissipation are located adjacent to the lower wall and at the centerline of the channel expansion. Also, by incrementing the Brinkman number in the hydrodynamically and thermally developing and fully developed zones, the values of total dissipation are increased.     

Cooling performance of a nanofluid flow in a heat sink microchannel with axial conduction effect

In this work, the forced convection of a nanofluid flow in a microscale duct has been investigated numerically. The governing equations have been solved utilizing the finite volume method. Two different conjugated domains for both flow field and substrate have been considered in order to solve the hydrodynamic and thermal fields. The results of the present study are compared to those of analytical and experimental ones, and a good agreement has been observed. The effects of Reynolds number, thermal conductivity and thickness of substrate on the thermal and hydrodynamic indexes have been studied. In general, considering the wall affected the thermal parameter while it had no impact on the hydrodynamics behavior. The results show that the effect of nanoparticle volume fraction on the increasing of normalized local heat transfer coefficient is more efficient in thick walls. For higher Reynolds number, the effect of nanoparticle inclusion on axial distribution of heat flux at solid–fluid interface declines. Also, less end losses and further uniformity of axial heat flux lead to an increase in the local normalized heat transfer coefficient.