Fluid flow pervasive

Pervasive fluid flow through a porous, permeable medium is described by Darcy s law, written here for three dimensions (cf. Bear, 1972) ... 

Hoisch T. D. (1991) The thermal effects of pervasive and channelized fluid flow in the deep crust. J. Geol. 99, 69-80. 

It is also important to note that these factors influence permeability on different scales as described by Brace (1984), permeabilities measured on the scale of a drill hole (30-300 m) can be much higher, due to widely spaced fractures, than those measured on a laboratory sample (5-15 cm). Thus drill hole permeabilities may be appropriate for estimating the flux of channeled fluids through the crust, but laboratory scale permeability, if properly measured, affords a better estimate of truly pervasive fluid flow. 

Convection in Melt Growth. Convection in the melt is pervasive in all terrestrial melt growth systems. Sources for flows include buoyancy-driven convection caused by the solute and temperature dependence of the density surface tension gradients along melt-fluid menisci forced convection introduced by the motion of solid surfaces, such as crucible and crystal rotation in the CZ and FZ systems and the motion of the melt induced by the solidification of material. These flows are important causes of the convection of heat and species and can have a dominant influence on the temperature field in the system and on solute incorporation into the crystal. Moreover, flow transitions from steady laminar, to time-periodic, chaotic, and turbulent motions cause temporal nonuniformities at the growth interface. These fluctuations in temperature and concentration can cause the melt-crystal interface to melt and resolidify and can lead to solute striations (25) and to the formation of microdefects, which will be described later. 

Figure 14 Selection of time-integrated fluid fluxes from the literature. The average regional, pervasive flow-dominated flux of ni(fluid) m(7ock) (2(r) denoted with diagonal ruled bar (computed using geometric mean ...

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