scholarly journals Viscous friction and heat flux for a partially ionized medium flowing in a plane channel with allowance for anisotropy of the transport coefficients

1967 ◽  
Vol 6 (3) ◽  
pp. 99-99
Author(s):  
E. G. Sakhnovskii
Keyword(s):  
Heat Flux ◽  
Transport Coefficients ◽  
Plane Channel ◽  
Viscous Friction ◽  
Partially Ionized

Experimental Verification of Heat-Flux Mitigation by Electromagnetic Fields in Partially-Ionized-Argon Flows

2009 ◽  
Vol 46 (2) ◽  
pp. 274-283 ◽  
Author(s):  
Ali Gülhan ◽  
Burkard Esser ◽  
Uwe Koch ◽  
Frank Siebe ◽  
Johannes Riehmer ◽  
...  
Keyword(s):  
Heat Flux ◽  
Electromagnetic Fields ◽  
Experimental Verification ◽  
Partially Ionized

scholarly journals Nonlinear Heat Transport in Superlattices with Mobile Defects

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1200 ◽  
Author(s):  
David Jou ◽  
Liliana Restuccia
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Conduction ◽  
Thermal Resistance ◽  
Heat Transport ◽  
Concentration Dependence ◽  
Transport Coefficients ◽  
Nonlinear Behavior ◽  
Strongly Nonlinear

We consider heat conduction in a superlattice with mobile defects, which reduce the thermal conductivity of the material. If the defects may be dragged by the heat flux, and if they are stopped at the interfaces of the superlattice, it is seen that the effective thermal resistance of the layers will depend on the heat flux. Thus, the concentration dependence of the transport coefficients plus the mobility of the defects lead to a strongly nonlinear behavior of heat transport, which may be used in some cases as a basis for thermal transistors.

Non-Newtonian stress, collisional dissipation and heat flux in the shear flow of inelastic disks: a reduction via Grad’s moment method

2014 ◽  
Vol 757 ◽  
pp. 251-296 ◽  
Author(s):  
Saikat Saha ◽  
Meheboob Alam
Keyword(s):  
Heat Flux ◽  
Shear Flow ◽  
Moment Tensor ◽  
Transport Coefficients ◽  
Navier Stokes ◽  
Restitution Coefficient ◽  
Moment Equations ◽  
Second Moment ◽  
Uniform Shear ◽  
Uniform Shear Flow

AbstractThe non-Newtonian stress tensor, collisional dissipation rate and heat flux in the plane shear flow of smooth inelastic disks are analysed from the Grad-level moment equations using the anisotropic Gaussian as a reference. For steady uniform shear flow, the balance equation for the second moment of velocity fluctuations is solved semi-analytically, yielding closed-form expressions for the shear viscosity $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\mu $, pressure $p$, first normal stress difference ${\mathcal{N}}_1$ and dissipation rate ${\mathcal{D}}$ as functions of (i) density or area fraction $\nu $, (ii) restitution coefficient $e$, (iii) dimensionless shear rate $R$, (iv) temperature anisotropy $\eta $ (the difference between the principal eigenvalues of the second-moment tensor) and (v) angle $\phi $ between the principal directions of the shear tensor and the second-moment tensor. The last two parameters are zero at the Navier–Stokes order, recovering the known exact transport coefficients from the present analysis in the limit $\eta ,\phi \to 0$, and are therefore measures of the non-Newtonian rheology of the medium. An exact analytical solution for leading-order moment equations is given, which helped to determine the scaling relations of $R$, $\eta $ and $\phi $ with inelasticity. We show that the terms at super-Burnett order must be retained for a quantitative prediction of transport coefficients, especially at moderate to large densities for small values of the restitution coefficient ($e \ll 1$). Particle simulation data for a sheared inelastic hard-disk system are compared with theoretical results, with good agreement for $p$, $\mu $ and ${\mathcal{N}}_1$ over a range of densities spanning from the dilute to close to the freezing point. In contrast, the predictions from a constitutive model at Navier–Stokes order are found to deviate significantly from both the simulation and the moment theory even at moderate values of the restitution coefficient ($e\sim 0.9$). Lastly, a generalized Fourier law for the granular heat flux, which vanishes identically in the uniform shear state, is derived for a dilute granular gas by analysing the non-uniform shear flow via an expansion around the anisotropic Gaussian state. We show that the gradient of the deviatoric part of the kinetic stress drives a heat current and the thermal conductivity is characterized by an anisotropic second-rank tensor, for which explicit analytical expressions are given.

Transport coefficients of partially ionized helium

1968 ◽  
Vol 2 (1) ◽  
pp. 17-32 ◽  
Author(s):  
R. S. Devoto ◽  
C. P. Li
Keyword(s):  
Electrical Conductivity ◽  
Chemical Equilibrium ◽  
Transport Coefficients ◽  
Tabular Form ◽  
True Value ◽  
First Approximation ◽  
Burnett Method ◽  
Partially Ionized

Transport coefficients are given in tabular form for partially ionized helium in chemical equilibrium at several pressures and for temperatures up to 35000 °K. Simplified theoretical expressions, derived with the Chapman—Enskog—Burnett method, were used for the computations. The convergence of the approximations to the electrical conductivity was also studied. It was found that the first approximation was within 17% of the true value at low ionization in contrast to recent results for argon where it could not be determined if even the fourth approximation had converged to the true value.

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