Radial flow permeability testing

Radial flow permeability testing apparatus. (Reprinted from J. R Feser et al. Journal of Power Sources 162 (2006) 1226-1231. With permission from Elsevier.)... 

For various reasons, laboratory permeability tests often yield results of limited value and in situ tests are generally thought to yield more reliable data The triaxial cell and the Rowe consolidation cell allow the direct measurement of permeability imder constant head with a back pressure and confining pressures more closely consistent with the field state. The Rowe cell allows either vertical or radial flow... 

Figure 13.1 Illustrations of devices for testing in-plane permeability of geotextile (a) parallel flow device (b) radial flow device.

In landfill-covering system, geotextiles are often used as a drainage layer for gas collection. Koemer et al. (1984) conducted tests on transmissivity to air of nonwoven geotextiles by a radial flow device similar to that illustrated in Fig. 13.1(b). Transmissivity to air was more than two orders higher than that to water imder comparable conditions. Furthermore, their test results showed that normal pressure did not have a significant influence on the air permeability of the geotextiles. 

Figure 6 indicates that many of the tested systems fulfill this requirement. Also, more than half of the surfactants in Figure 6 adsorb at less than 0.4 mg/g, and this adsorption results in a reasonable distance of propagation (200 m) in the high-permeability layer. The distances plotted in Figure 8 are conservative because flow in a reservoir that requires sweep improvement measures is not likely to be completely cylindrical but takes place through preferential flow channels. The calculations would also be more favorable for a linear (as opposed to radial) drive pattern. 

The observation of large shell concentration gradients at the periphery of the fibre bundle suggests race tracking phenomena may have a significant impact on module performance. To test this hypothesis, the hydraulic permeability for the shell side flow was assumed to have the following dependence on the radial coordinate ... 

Determination of the permeability in the field can be done by measuring the time it takes for a tracer to move between two test holes. As with pumping tests, this tracer technique is based on the assumption that the aquifer is homogeneous and that observations taken radially at the same distance from the well are comparable. This method of assessing permeability requires that injection and observation wells be close together (to avoid excessive travel time) and that the direction of flow be known so that observation holes are correctly sited. 

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