Mean-Parameter Modeling of Oscillating Flow

1986 ◽  
Vol 108 (3) ◽  
pp. 513-518 ◽  
Author(s):  
D. Gedeon
Keyword(s):  
Exact Solution ◽  
Temperature Gradient ◽  
Fluid Shear Stress ◽  
Oscillating Flow ◽  
Parallel Plates ◽  
Longitudinal Temperature Gradient ◽  
Longitudinal Temperature ◽  
The Mean ◽  
The Difference ◽  
Energy Equations

After looking at the exact solution for laminar incompressible oscillating flow between parallel plates with a longitudinal temperature gradient, the momentum and energy equations are reast in terms of mean (section average) velocity and temperature. It is shown that fluid shear stress and normal temperature gradient at the wall are amplified and phase shifted compared to the steady-flow case and some practical equations for friction factor and Nusselt number are given. However, the mean-parameter solution differs from the exact solution in regard to net advected energy, thereby prompting the introduction of an apparent enhanced fluid conductivity to account for the difference.

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.

Laminar gravitational convection of heat in dead-end channels

1981 ◽  
Vol 110 ◽  
pp. 97-113 ◽  
Author(s):  
Terry W. Sturm
Keyword(s):  
Temperature Gradient ◽  
Closed Form ◽  
Closed Form Solution ◽  
Form Solution ◽  
Gravitational Convection ◽  
Longitudinal Temperature Gradient ◽  
Dead End ◽  
Longitudinal Temperature ◽  
Surface Heat Transfer Coefficient ◽  
Energy Equations

A closed-form solution of the coupled momentum and thermal energy equations is obtained for laminar gravitational circulation of water resulting from a longitudinal temperature gradient in a dead-end channel. The temperature gradient is determined by the rate of heat loss from the water surface. The solution is shown to be dependent on a modified Rayleigh number which involves the local surface heat-transfer coefficient. An experimental study was conducted, and the results are compared with the closed-form solution.

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.

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