Boundary general

Distillation into curved boundary, general separation heuristics for, 22 318 Distillation lines (residue curve maps), 8 790-793... 

Typically, there are two types of boundaries in reacting flows. The first is a solid surface at which a reaction may be occurring, where the flow velocity is usually set to zero (the no-slip condition) and where either a temperature or a heat flux is specified or a balance between heat generated and lost is made. The second type of boundary is an inflow or outflow boundary. Generally, either the species concentration is specified or the Dankwerts boundary condition is used wherein a flux balance is made across the inflow boundary (64). The gas temperature and gas velocity profile are usually specified at an inflow boundary. At outflow boundaries, choices often become more difficult. If the outflow boundary is far away from the reaction zone, the species concentration gradient and temperature gradient in the direction of flow are often assumed to be zero. In addition, the outflow boundary condition on the momentum balance is usually that normal or shear stresses are also zero (64). 

The definition of low-angle grain boundaries generally covers the range of misorientations from 0° to 10°. In this regime, the grain boundary plane can be considered to be a linear array of separated dislocation cores. For [001] tilt boundaries in YBCO, the boundary plane will be composed of [100] or [010] dislocations, as shown in Fig. 11.6 (for YBCO the small distortion between the a- and fi-axes needs to be incorporated for quantitative models, but structurally results in no observable differences in the dislocation cores). 

While most of the terms recommended are widely accepted, common misconceptions persist, particularly with regard to fiiimel flow and the different zones of behaviour in a mass flow hopper that incorporates a section of non-converging boundary. General use of the above definitions of flow regimes and their local zones of composite flow behaviour will lead to a better understanding of the various mechanisms that are active during flow processes, and also secure a common international basis for descriptions in technical publications. 

Peryman E.C.W., Grain-boundary general corrosion of high-purity aluminium and hydrochloric acid, Journal of Metals, vol. 5, 1953, p. 911-917. 

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