Flow In Neighborhood Research Articles

Boundary layer theory approach to the concentration layer adjacent to a ceiling wall at impinging region of a hydrogen leakage

In this article, the steady-state concentration boundary layer adjacent to a ceiling wall of a stagnation-point flow region resulting from hydrogen impinging leakage is investigated. Flow in neighborhood of the stagnation point is treated as Hiemenz flow, while the concentration equation governs the concentration distribution in the boundary layer. The assumptions of the boundary layer theory are invoked to simplify both the momentum and the concentration equations. Comparison between the CFD simulation and the current boundary layer approximation shows a good agreement. Both momentum and concentration boundary layer thicknesses are estimated as well as local friction factor and local mass transfer. Also, the study is extended to include some cases of unsteady leakage. The effects of the unsteadiness parameter on the local friction factor and mass transfer rate as well as momentum and concentration boundary layer thicknesses are analyzed.

Surface-Wave Propagation Over a Coated Plane Conductor

A TM-type wave is assumed propagated parallel to the surface of a plane conductor coated with a thin layer of dielectric. This wave is similar to the wave propagated over a dielectric-coated wire of circular cross section, discussed by Dr. Goubau in the references. Analysis of the cylindrical type wave requires the use of Hankel functions, while the wave over a plane surface may be described by simpler functions, namely, trigonometric functions in the dielectric layer and real exponential functions in the adjacent air region. The calculations thus are considerably simplified and the wave properties more readily observed. Basic equations are developed for both dielectric layer and air regions, which indicate a criss-cross or multiply reflected wave in the dielectric and a unidirectional wave in the air. Equations are developed also for the electric flux line shapes, power propagated over the cross section, concentration of power flow in neighborhood of the film, attenuation due to conductor wall loss and dielectric film loss. Numerical calculations are given for five film thicknesses varying from 0.0001 to 0.01 meter and for five frequencies ranging from 3×108 to 3×1010 cycles per second.