Angular pore

Fig. 1-2. Angular pore spaces in natural porous media (< /) scanning HitIiom niiiiuginpli (SHM) nl a soil composed of line-sand, sill, and clay (Wank I oslierg, 10H >). I/O SI M nl udciiim saturated montmorillonitc, (< ) liquid retention in triangularand cyJindiiud mu > ...

The discussions in the preceding sections illustrate several shortcomings of cylindrical capillaries representation (BCC model), hence the need for a more realistic representation of pore space geometry. Some studies have used angular pore systems lot observation and modeling of capillary phenomena in porous... 

The results for flow on a single fracture surface are incorporated in the derivation of hydraulic properties of unsaturated fractured rock mass. Liquid retention and hydraulic conductivity in partially saturated fractured porous media are modeled in angular pores and slit-shaped spaces representing rock matrix and fractures, respectively. A bimodal distribution of pore sizes and apertures accounts for the two disparate pore scales and porosity. These considerations provide a framework for derivation of retention and hydraulic conductivity functions for fractured porous media (Or Tuller, 2001). 

A new pore geometry model was proposed for a more realistic representation of pore space of natural porous media using angular pore geometry and slit-shaped spaces for surface area considerations. 

Simple expressions for capillary phenomena in angular pores based on angularity shape factor Fn and curvature only, were developed. 

Tuller, M., D. Or, and L.M. Dudley. 1999. Adsorption and capillary condensation in porous media Liquid retention and interfacial configurations in angular pores. Water Resour. Res. 35 1949-1964. Tuller, M., and D. Or, 2001, Hydraulic conductivity of variably saturated porous media Film and corner flow in angular pore space. Water Resour. Res. (In press.) van Genuchten, M.Th. 1980. A closed-form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Sci. Soc. Am. J. 44 892-898. 

The long-slit, i.e. one-dimensional, angular correlation (ACAR) apparatus used for these studies is similar to that shown in Figure 1.6. Silica aerogel (see subsection 1.5.2) was employed as a convenient source of positronium, emitted into the space between the pores. The chamber could be evacuated and the high purity gases under investigation then... 

The angular intensity distribution of X-rays refracted by fibers or spherical pores has been approximated by Hentschel et al. [3]. Quantitative X-ray refraction analysis is implemented at a constant scattering angle of about two minutes of arc and at a fixed wavelength. The refraction value C is proportional to the absolute internal surface density S. With dp denoting the sample thickness the relationship can be given by ... 

Considering the effects of the radial and the angular components of the velocity vector of intraparticle convective flow in the pores of the spherical particles. 

The following assumptions were made in formulating this model 1) there is no solute adsorption to the stationary phase, 2) the porous particles which form the stationary phase are of uniform size and contain pores of identical size, 3) there are no interactions between solute molecules, 4) the mobile phase is treated as a continuous phase, 5) the intrapore diffusivity, the dispersion coefficient and the equilibrium partition coefficient are independent of concentration. The mobile phase concentration. Cm, is defined as the mass (or moles) per interstitial volume and is a function of the axial coordinate z and the angular coordinate 0. The stationary phase concentration, Cs, is defined as the mass per pore volume and depends on z, 6 and the radial coordinate, r, of a spherical coordinate system whose origin is at the center of one of the particles. 

---