Influence of longitudinal temperature gradient on light propagation in lens-like medium

1969 ◽  
Vol 17 (2) ◽  
pp. 1021-1024
Author(s):  
O. G. Martynenko ◽  
V. L. Kolpashchikov ◽  
B. M. Berkovskii
Keyword(s):  
Temperature Gradient ◽  
Light Propagation ◽  
Longitudinal Temperature Gradient ◽  
Longitudinal Temperature

scholarly journals Heat and Mass Transport in Carbon Nantubes

2010 ◽  
Author(s):  
Junichiro Shiomi ◽  
Carl Fredrik Carlborg ◽  
Shigeo Maruyama
Keyword(s):  
Molecular Dynamics ◽  
Temperature Gradient ◽  
Mass Transport ◽  
Small Diameter ◽  
Elastic Interaction ◽  
Heat And Mass Transport ◽  
Longitudinal Temperature Gradient ◽  
Longitudinal Temperature ◽  
Argon Matrices ◽  
Dynamics Simulations

We have investigated heat and mass transport in single-walled carbon nanotubes (SWNTs) using molecular dynamics methods. Particular attention was paid on the non-equilibrium dynamics at the interface between SWNT and other materials, which strongly manifests in nanoscale. In the first part, we have investigated the heat transport through the interface between SWNTs and surrounding argon matrices in liquid and solid phases. By analyzing the energy relaxation from SWNT to the matrices using non-stationary molecular dynamics simulations, elastic and inelastic thermal energy transports across the interface were separately quantified. The result reveals that the elastic interaction transports energy much faster than the inelastic one, but carries much smaller energy due to slow intra-SWNT phonon relaxation. In the second part, we have investigated a possibility to utilize nonequilibrium thermal interface to transport water through an SWNT. By applying the longitudinal temperature gradient to the SWNT, it is demonstrated that the water cluster is efficiently driven at average acceleration proportional to the temperature gradient. However, the transport simulations with a junction of two different SWNTs suggest that an angstrom diameter difference may result in a significant drag for small diameter SWNTs.

Thermal Instability in Plane Poiseuille Flow

1970 ◽  
Vol 92 (1) ◽  
pp. 61-68 ◽  
Author(s):  
W. Nakayama ◽  
G. J. Hwang ◽  
K. C. Cheng
Keyword(s):  
Temperature Gradient ◽  
Flow Direction ◽  
Characteristic Parameter ◽  
Parallel Plates ◽  
Longitudinal Temperature Gradient ◽  
Longitudinal Temperature ◽  
Longitudinal Wall ◽  
Tollmien Schlichting ◽  
Prandtl Numbers ◽  
Basic Temperature

The conditions marking the onset of longitudinal columnar vortices due to buoyant forces are studied for fully developed laminar flow between two infinite horizontal parallel plates with nonlinear basic temperature profile. The wall temperatures at the bottom and top plates, T1 and T2, respectively, are assumed to vary linearly in the main flow direction. The nonlinear basic temperature distribution and connective motion due to longitudinal disturbance component give rise to the influence on stability criteria: This influence may be expressed by a characteristic parameter representing the effect of longitudinal temperature gradient. Numerical values for critical Rayleigh numbers based on temperature difference, T1 − T2, are found for various Prandtl numbers and the parameter μ characterizing the effect of longitudinal wall temperature gradient. An increase in value for μ reduces the critical Ra further to a value less than 1708 when T1 > T2, and this tendency becomes pronounced as Pr increases. Results for the cases T1 ≦ T2 also show that the vortex rolls can be caused by the effect of longitudinal temperature gradient. Tentative discussion in terms of Richardson number is made to define the region where columnar vortices have priority of appearance over two-dimensional Tollmien-Schlichting waves. The computed secondary flow streamlines and perturbation temperatures show that the mode of convection motion is also affected by the parameter μ.

scholarly journals Rotating magnetic field effect on convection and its stability in a horizontal cylinder subjected to a longitudinal temperature gradient

2010 ◽  
Vol 664 ◽  
pp. 108-137 ◽  
Author(s):  
D. V. LYUBIMOV ◽  
A. V. BURNYSHEVA ◽  
H. BENHADID ◽  
T. P. LYUBIMOVA ◽  
D. HENRY
Keyword(s):  
Magnetic Field ◽  
Temperature Gradient ◽  
Prandtl Number ◽  
Cross Section ◽  
Rotating Magnetic Field ◽  
Shear Mode ◽  
Convective Flows ◽  
Longitudinal Temperature Gradient ◽  
Longitudinal Temperature ◽  
The Cross

A rotating magnetic field (RMF) is used in crystal growth applications during the solidification process in order to improve the crystal quality. Its influence on the convective flows in molten metals and on their stability is studied here in the case of a horizontal infinite cylindrical channel subjected to a longitudinal temperature gradient. The steady convective flows, which correspond to the usual longitudinal counterflow structure, with four vortices in the cross-section for non-zero Prandtl number, Pr, are modified by the RMF (parametrized by the magnetic Taylor number Tam). For zero Prandtl number, the flow in the cross-section corresponds to circular streamlines and the longitudinal flow structure is moved in the direction of the magnetic field rotation, with a decrease in its intensity and an asymptotic variation as 1/Tam. For non-zero Prandtl numbers, depending on the respective values of Tam on one side and Prandtl and Grashof numbers on the other side, different structures ranging from the circular streamlines with transport by rotation of the longitudinal velocity and the temperature field, to the more usual counterflow structure almost insensitive to the RMF with four cross-section vortices, can be obtained. The decrease in the flow intensity with increasing Tam is also delayed for non-zero Pr, but the same asymptotic limit is eventually reached. The stability analysis of these convective flows for Tam = 0 shows a steep increase of the thresholds around Pr = Prt,0 ≈ 3 × 10−4, corresponding to the transition between the usual counterflow shear mode and a new sidewall shear mode. This transition is still present with an RMF, but it occurs for smaller Pr values as Tam is increased. Strong stabilizing effects of the rotating magnetic field are found for Pr < Prt,0, particularly for Pr = 0 where an exponential increase of the threshold with Tam is found. For Pr > Prt,0 (i.e. in the domain where the sidewall instability is dominant), in contrast, the stabilization by the RMF is weak.

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