Fracture Junctions Research Articles

Laboratory and simulation studies of solute transport in fracture networks

Physical and numerical fracture network models have been used to analyze the transport of conservative solutes in systems of parallel‐sided fractures. The processes controlling dispersion in fracture systems that are explicitly simulated by the numerical model are (1) development of a velocity profile within individual fractures, (2) transverse molecular diffusion between streamlines, both within fractures and at fracture junctions, and (3) advection with the bulk fluid through a system of fractures with a range of hydraulic gradients and apertures. The first two processes, referred to as microdispersion, are often assumed to be secondary to the third, referred to as macrodispersion. The validity of this assumption is, however, highly dependent on the hydrodynamics of the system under consideration. Data collected from a physical model of a fracture network are used to validate a numerical model that explicitly simulates all three transport processes. The numerical model is then used to evaluate the relevance of microdispersion processes in a system where macrodispersion is significant.

Streamline routing through fracture junctions. Technical note : Hull, L C; Koslow, K N Water Resour ResV22, N12, Nov 1986, P1731–1734

Streamline routing through fracture junctions. Technical note : Hull, L C; Koslow, K N Water Resour ResV22, N12, Nov 1986, P1731–1734

Streamline routing through fracture junctions

A series of laboratory tests was conducted to determine routing criteria for streamlines through fracture junctions. These tests showed that two criteria are all that is necessary to route streamlines through any two‐dimensional junction under laminar flow conditions. These criteria are (1) that streamlines do not cross and (2) that flow along adjacent streamlines must be in the same direction. Using these two criteria, a unique distribution of streamlines can be determined for both continuous and discontinuous fracture junctions.

The effect of powder metallurgy process parameters on mechanical properties of micro and nano-iron powder

The ever-increasing development of applying the iron pieces made by powder metallurgy in car industries and other usages depends on making pieces with high density and consequently acceptable physical and mechanical properties. Regarding the effect of decrease in the powder bits’ size on improvement of the mechanical characteristics and on decrease in the temperature of sinter, the experiments on the pure iron powder with the bits’ size of 5, 45, 63 micron in which 20% of iron nanopowder was added to the powder with the bits’ size of 45 micron, have been studied. Mere iron nanopowder also was applied for experiments. Pieces are compacted under 300-850 MPa and lubricants by0.4 and 0.6 percent of the total weight was mixed with the powders. Various amounts of sintering time and sintering temperature were considered for the sintering of the samples. The survey suggested that applying micro powders resulted in an increase in the linear density and the strength at the relatively high temperatures and high keeping times. Sintering temperature and shrinkage has declined considerably with the decrease in the powder size and as a result the strength increases. High strength for products made by smaller powders under high pressures and low sintering temperatures using lubricated frame wall are obtained. SEM pictures from the fracture junctions of the samples show the decrease in porosity due to the close impact of the smaller powder size.