Determination of loads applied perpendicularly to the outer boundary of a ring using coefficients of influence

A procedure is explained to determined the amount of several pairs of diametrical loads applied to the outside boundary of a ring when stresses at selected points of the inside or outside boundaries are known. Coefficients of influence are used, following an approach similar to the one presented in a previous paper. Examples of application are given and the possible increase in precision is shown when the number of points of measurements is larger than the number of loads to be determined.     

Magnetic resonance imaging of flow-distributed oscillations

The formation of stationary concentration patterns in a packed-bed reactor (PBR), using a manganese-catalyzed Belousov-Zhabotinsky (BZ) reaction in a mixed sulfuric-phosphoric acid medium, was studied using magnetic resonance imaging (MRI). The PBR was composed of a column filled with glass beads, which was fed by a continuous stirred tank reactor (CSTR). As the reactor is optically opaque, investigation of the three-dimensional (3D) structure of these reaction-diffusion-advection waves is not possible using conventional image capture techniques. MRI has been used to probe this system and the formation, 3D structure, and development of these waves has been studied. At reactor startup, traveling waves were observed. After this initial period the waves stabilized and became stationary. Once fixed, they were found to be remarkably stable. There was significant heterogeneity of the reaction fronts, which were not flat, as would be expected from a plug-flow reactor. Instead, the reaction wave fronts were observed to be conical in shape due to the local hydrodynamics of the bed and specifically the higher velocities and therefore lower residence times close to the wall of the reactor.     

Fast emulsion droplet sizing using NMR self-diffusion measurements

Emulsion droplet sizing using pulsed field gradient (PFG) nuclear magnetic resonance (NMR) is a well-established technique. Traditionally these measurements require total acquisition times of typically 5-20 min per sample, which severely limits our ability to use this method to study dynamic processes. Here we present the application and verification of an NMR pulse sequence, Difftrain, which enables emulsion droplet size distributions to be measured in 3-10 s. We have previously introduced applications of Difftrain (C. Buckley, K.G. Hollingsworth, A.J. Sederman, D.J. Holland, M.L. Johns, L.F. Gladden, J. Magn. Reson. 161 (2003) 112-117), including the droplet sizing of a single unimodal emulsion sample. In this paper, several model emulsions containing different oils are measured and the results compared directly with sizing provided by laser scattering. In this manner, the Difftrain method is verified and its possibilities and limitations are explored. Guidelines are proposed for the range of droplet sizes for which accurate results can be produced. The Difftrain technique opens up the possibility of studying non-equilibrium emulsions; a study of the in situ emulsification of a 21% v/v water-in-silicone oil emulsion is presented.     

Displacement propagators of brine flowing within different types of sedimentary rock

This paper explores the correlation between different microstructural characteristics of porous sedimentary rocks and the flow properties of a Newtonian infiltrating fluid. Preliminary results of displacement propagator measurements of brine solution flowing through two types of sedimentary rock cores are reported. The two types of rocks, Bentheimer and Portland, are characterized by different porosities, pore-size distributions and permeabilities. Propagators have been measured for brine flow rates of 1 and 5 ml/min. Significant differences are seen between the propagators recorded for the two rocks, and these are related to the spatial distribution of porosity within these porous media.     

Magnetic resonance velocity imaging of liquid and gas two-phase flow in packed beds

Single-phase liquid flow in porous media such as bead packs and model fixed bed reactors has been well studied by MRI. To some extent this early work represents the necessary preliminary research to address the more challenging problem of two-phase flow of gas and liquid within these systems. In this paper, we present images of both the gas and liquid velocities during stable liquid–gas flow of water and SF₆ within a packing of 5 mm spheres contained within columns of diameter 40 and 27 mm; images being acquired using ¹H and ¹⁹F observation for the water and SF₆, respectively. Liquid and gas flow rates calculated from the velocity images are in agreement with macroscopic flow rate measurements to within 7% and 5%, respectively. In addition to the information obtained directly from these images, the ability to measure liquid and gas flow fields within the same sample environment will enable us to explore the validity of assumptions used in numerical modelling of two-phase flows.     

MRI velocimetry and lattice-Boltzmann simulations of viscous flow of a Newtonian liquid through a dual porosity fibre array.

Viscous flow through fibrous porous media has considerable importance in a number of industrial processes including, in particular, resin transfer molding. In this paper magnetic resonance flow imaging techniques are used to visualize flow of a Newtonian liquid through a dual porosity structure. Of particular interest in these studies is the transition in the flow as the liquid moves from the open region into the fiber array. The ability of lattice-Boltzmann simulations to predict the visualized flow fields is presented and discussed.