Robert A. Greenkorn

Laboratory observation of nonlocal dispersion

This work presents the results of a one-dimensional experimental investigation of contaminant transport in heterogeneous porous media. The usual transport equations fail to adequately predict dispersion in such systems, and new theories to account for the distinctions have not yet been examined experimentally. We use a one-dimensional porous media which is heterogeneous on the scale of observation to determine if the phenomena predicted by the new theories are observable.The experimental media are constructed from distinct layers of spherical glass beads packed into cylindrical columns of Lucite. Flow was in the direction perpendicular to the layers. Dispersion was measured by recording the concentration of a chloride tracer as a function of time and position. The scale of measurement was finer than the scale of the heterogeneity. The results show that the mixing between miscible fluids was affected by transitions in the system parameters, before the transitions were encountered by the mixing zone. This newly observed phenomenon has been interpreted as a nonlocal effect, and it begins to verify the new predictive theories.

Chain-of-rotators group contribution equation of state

Abstract A group contribution equation of state is developed from the chain-of-rotators equation and parameters for 20 groups are reported. It is shown that the new equation allows predictions with good accuracy of phase equilibrium and volumetric properties for a variety of non-polar fluids and their mixtures over wide ranges of temperature and pressure.

Bubble pressures and vapor-liquid equilibria for four binary hydrocarbon mixtures☆

Bubble pressures and vapor-liquid equilibria are reported for four binary hydrocarbon mixtures at three temperatures: (cyclohexane + benzene). (methylcyclopentane + benzene), (ethylbenzene + n-heptane), and (p-xylene + n-heptane). The isothermal dependence of bubble pressure on liquid-phase composition is determined in a static apparatus. Equilibrium vapor-phase compositions are calculated from Barkers procedure using the three-parameter Redlich Kister equation for the excess Gibbs free energy.

Momentum, heat, and mass transfer fundamentals

Essentials the mass balances the energy balances the momentum balances application of dimensional analysis momentum transfer in fluids heat transfer models mass transfer model. Appendices: vector and tensor operations error function nomenclature.

Experimental investigation of characteristic length scale in periodic heterogeneous porous media

An experimental investigation of scale-dependent dispersion in periodic heterogeneous porous media was conducted. Models with two-, three- and four-layer periodic heterogeneities were constructed to investigate the effect of heterogeneity size on the scale-dependence of dispersion. Longitudinal dispersion coefficients were determined as a function of column length by measuring the breakthrough of a continuous injection of potassium chloride tracer solution. Chloride ion concentration was monitored by recording the millivolt potential of silver/silver chloride electrodes placed at intervals along the length of the column. In all three models, dispersion appeared to be scale dependent up to a distance of approximately 20–30 times the size of the repeated heterogeneity group (hydraulic unit). Because all three models suggested a similar dependence, it was concluded that a medium with periodic heterogeneity may likely be characterized by the scale of its hydraulic unit.

Concentration and velocity field measurements by magnetic resonance imaging in aperiodic heterogeneous porous media

Magnetic resonance imaging (MRI) techniques were investigated as a means to obtain concentration and velocity field measurements for the verification of a stochastic model for conservative chemical transport. MRI techniques were successfully applied to obtain one-dimensional breakthrough images and two-dimensional velocity images along the length of an aperiodic heterogeneous porous medium. Experimental moment data showed the concentration field in the experimental model to be slightly positively skewed. Velocity images showed the velocity field to be relatively uniform with no channeling or preferential flow behavior. Measured covariance functions showed evidence of negative correlation in the velocity field. The detailed spatial information provided by these imaging experiments has demonstrated that MRI is a valuable tool for obtaining experimental data for the verification of existing theoretical models.

The permeability tensor for anisotropic nonuniform porous media

Abstract This paper describes a study of the permeability of anisotropic, nonuniform porous media. The approach is through a statistical model of the microstructure of the porous media. Using a capillary-type model with a distribution of pore sizes and orientations, we show that the permeability can be described by a second-order symmetric tensor regardless of the preferential orientation of the pores in the microstructure. We also show that an ergodic assumptions is not always true—spatial averages cannot generally be interchanged with mathematical expectations.

Experimental Investigation of Mixing in Aperiodic Heterogeneous Porous Media: Comparison with Stochastic Transport Theory

An electrochemical technique was used to measure concentration distributions in an aperiodic heterogeneous model for comparison with a stochastic transport theory. Four identical columns, each filled with a homogeneous distribution of glass beads, were threaded together to create a single model with aperiodic heterogeneity. The layers in the model were arranged in different ways providing 24 realizations of the permeability distribution. Comparisons between experimental moment data and moments of simulated mean concentration distributions showed that the model was not able to accurately predict experimentally observed mixing behavior.

An experimental investigation of dispersion in layered porous media

Experiments were run in three linear, homogeneous, nonuniform porous media constructed in lucite columns using spherical glass beads. The columns were also joined end to end to create an in series layered heterogeneous porous media. Each column, all combinations of columns and several permutations were studied with a factorial experimental design to determine the effects of porosity, permeability, velocity, length, and column order upon dispersion. Attempts to predict the heterogeneous results from the homogeneous results were made, and a statistical regression based on the factorial design was calculated. Results showed that no simple averaging procedure accurately predicted the heterogeneous results. The statistical regression showed permeability, velocity, viscosity, length and column order to be significant.

An Experimental Investigation of the Effect of Idealized Heterogeneity on the Dispersion of Miscible Fluids

Laboratory experiments on dispersion of miscible fluids in a porous medium have been performed. Dimensionally scaled two-dimensional models were packed with both homogeneous and idealized heterogeneous permeability distributions. Longitudinal dispersion coefficients were calculated by mapping the flow into the streamline-equipotential coordinate system. The results of these experiments indicate that the dispersion coefficient is not a function of the spatial scale of the system provided that the permeability distribution is preserved as the system dimension is increased. Also, it was found that an inclusion of permeability differing from the surrounding medium could result in both Gaussian and non-Gaussian tracer distributions depending upon the location of the inclusion, and systems with heterogeneous permeability distributions sometimes resulted in dispersion similar to that for homogeneous media. In some instances, the dispersion everywhere within the system appeared to be Fickian, but when the dispersion was monitored at the withdrawal point from the system, the dispersion appeared to be non-Fickian.