Velocity Of Moving Boundary Research Articles

Analysis of Pressure and Production Transient Characteristics of Composite Reservoir with Moving Boundary

The mathematical model of composite reservoir has been widely used in well test analysis. In the process of oil recovery, due to the injection or replacement of the displacement agent, the model boundary can be moved. At present, the mathematical model of a composite reservoir with a moving boundary is less frequently studied and cannot meet industrial demand. In this paper, a mathematical model of a composite reservoir with a moving boundary is developed, with consideration of wellbore storage and skin effects. The characteristics of pressure transient in moving boundary composite reservoir are studied, and the influences of parameters, such as initial boundary radius, moving boundary velocity, skin factor, wellbore storage coefficient, diffusion coefficient ratio, and mobility ratio on pressure and production, are analyzed. The moving boundary effects are noticeable mainly in the middle and late production stages. The proposed model provides a novel theoretical basis for well test analysis in these types of reservoirs.

Numerical Investigation of Shell Formation in Thin Slab Casting of Funnel-Type Mold

The key issue for modeling thin slab casting (TSC) process is to consider the evolution of the solid shell including fully solidified strand and partially solidified dendritic mushy zone, which strongly interacts with the turbulent flow and in the meantime is subject to continuous deformation due to the funnel-type mold. Here an enthalpy-based mixture solidification model that considers turbulent flow [Prescott and Incropera, ASME HTD, 1994, vol. 280, pp. 59–69] is employed and further enhanced by including the motion of the solidifying and deforming solid shell. The motion of the solid phase is calculated with an incompressible rigid viscoplastic model on the basis of an assumed moving boundary velocity condition. In the first part, a 2D benchmark is simulated to mimic the solidification and motion of the solid shell. The importance of numerical treatment of the advection of latent heat in the deforming solid shell (mushy zone) is specially addressed, and some interesting phenomena of interaction between the turbulent flow and the growing mushy zone are presented. In the second part, an example of 3D TSC is presented to demonstrate the model suitability. Finally, techniques for the improvement of calculation accuracy and computation efficiency as well as experimental evaluations are also discussed.

Numerical study of gas-solid reactive flow in a cylinder

A theoretical model is described for the numerical simulation of unsteady gas-solid reactive flow in packed beds of granular propellants in a tubular geometry. The approach couples continuity, momentum and energy equations in each phase along with porosity and granular stresses. Propellant bed combustion process is neglected, but the mass flow rate due to the combustion is derived using a pressure-based burning rate correlation. As the burning of solid propellant begins, pressure, temperature, density and other gas parameters begin to change rapidly. To catch these changes, a CFD approach with explicit McCormack method is used to solve the coupled system of equations. A moving mesh is used to consider the moving boundary. Pressure history, moving boundary velocity and other parameters of the mixture are obtained and compared with other numerical data.

New method for calculating charge density in electrochemical systems

A new model for calculating the influence of charge density on electrolyte mass transport has been developed. This model is derived from Poisson's equation for charge density and is implemented as an algebraic charge density correction. Use of this method greatly improves the computational efficiency of electrolyte mass transport modelling by avoiding the solution of Poisson's equation. The new correction was used in the simulation of a moving boundary experiment. The predicted moving boundary velocity matched experimental results. Furthermore, the performance of this model was compared with the operator splitting algorithm of Evitts and Watson. Use of the new charge density model resulted in improved computational efficiency, numerical stability and accuracy.

NUMERICAL RESOLUTION OF A PHASE CHANGE PROBLEM WITH ZERO LATENT HEAT

Two numerical methods to simulate Ike behavior of a class offree-boundary thermal systems are presented and compared. The state of the system is governed by the conduction equation, where an isotherm defines the moving boundary for which a Neumann condition is considered. Unlike the classical Stefan problem, the moving boundary velocity does not appear explicitly in the heal balance One method is based on the Friedman transformation and leads to a variational inequality defined on a fixed domain. Computation of the front velocity is not required The other method uses the Landau transformation, leading to a new state equation of the convection-conduction type on a fixed domain. The convective part in the equation is due to the moving boundary. Estimation of the front velocity is obtained from the field temperature in the neighborhood of the boundary The comparison between the two methods is performed on two examples—a freezing and a melting case—the exact solutions of which are known.

Physical Properties of Acinetobacter Glutaminase-Asparaginase with Antitumor Activity

Abstract Acinetobacter glutaminase-asparaginase has been shown to consist of 4 subunits (molecular weight 33,000) by sedimentation equilibrium in 5.5 m guanidine HCl and electrophoresis in sodium dodecyl sulfate on polyacrylamide gels after cross-linking the protein with dimethyl suberimidate. Moving boundary velocity experiments showed that most of the native enzyme sediments as the tetramer (s20,w = 7.42 ± 0.03 S). On the other hand, equivalent boundary calculations always showed a smaller s20,w. Analytic sedimentation equilibrium experiments revealed a tetramerdimer dissociation with a dimer molecular weight of 69,000 ± 3000. The molecular weight on calibrated Sephadex G-200 and Bio-Gel P-200 was 97,000 and 93,000, respectively, which may indicate reversible dissociation. The hydrolysis of 5-diazo-4-oxonorvaline was used to determine the sedimentation coefficient of the active species. Sedimentation of the enzyme in 5-diazo-4-oxonorvaline showed complex patterns with ultraviolet optics due to protein absorbance. A new double sector cell was devised which allows layering of enzyme into both sectors simultaneously, cancelling the absorbance of the enzyme. The s20,w value for the species which degraded 5-diazo-4-oxonorvaline was 7.6 ± 0.2 S. By matching zone sedimentation and active enzyme experiments, enzyme species smaller than tetramer were shown to have 4% or less of the activity of the tetramer.