Mathematical Modeling of Tidal Effects in Groundwater

This paper presents a special use of the linear poroelasticity theory to describe tidally induced groundwater oscillations. Two models of oscillation inducing mechanism make use of this theory to predict groundwater level fluctuations. The numerical solutions of both models are presented and compared with well water level measurement obtained in Police Basin, north-east Bohemia.     

Investigation of Crystal Growth in Enzymatically Induced Calcite Precipitation by Micro-Fluidic Experimental Methods and Comparison with Mathematical Modeling

Transport in Porous Media - Enzymatically induced calcite precipitation (EICP) is an engineering technology that allows for targeted reduction of porosity in a porous medium by precipitation of...     

Thermoelasticity constants of polycrystals

Exact formulas are derived for the thermoelasticity constants of macroscopically homogeneous polycrystals. A method described earlier [1] is used as the basis. It is assumed that the local parameters form an ergodic homogeneous random field. No restriction is imposed on the degree of anisotropy of the crystals.     

Mathematical Modeling and Parameter Identification of a Planar Servo-Pneumatic Test Facility. Part I: Mathematical Modeling and Computer Simulation

High quality multi-axis test facilities used for testing heavy loads and large structures of industrial equipment are usually simulated, designed and controlled based on reduced model equations neglecting the inertia properties of the actuators. The design and control of servo-pneumatic test facilities used for testing small and light structures must take into account extended test facility models including the various inertia properties of the actuators. In this paper (Part I) an extended test facility model is presented including the various inertia properties and joints of the actuators. These extended model equations are represented in a form well suited to be directly implemented in control algorithms based on exact linearization techniques for real time control. This is done by stepwise projecting the inertia properties of the various actuator housings and actuator pistons down to the common mass of the test table and payload. The resulting extended model equations have the same form as the reduced model equations. They only include more complex system matrices and vector functions. These compact model equations turn out to be suitable for an efficient nonlinear controller design of these test facilities. Computer simulations and associated laboratory experiments show the necessity to use extended model equations in case of testing small and light structures. In Part II of this paper [1] the inertia parameters of the planar test facility will be identified in laboratory experiments.     

Modeling of Wormhole Growth in Cold Production

Cold production is a non-thermal process in which sand is intentionally produced with the oil in order to enhance oil recovery. Two experiments were performed to investigate the effect of producing large quantities of sand on the overall permeability of a formation. A large high porosity channel (wormhole) was observed in both experiments. A model of wormhole growth was successfully tested in two sand production experiments simulating the growth of a wormhole from a perforation in a vertical well. The produced volumes of oil, sand and gas, the pressure distribution along the pack and the final length of the wormholes were well predicted. The two sand packs had significantly different cohesive strengths. The strength of the sand did not have a significant effect on the growth of the wormholes. The formation of tensile failure bands at the wormhole surface, as observed in the experiments, may weaken the sand and allow it to be fluidized more easily. This weakening effect would explain the lower pressure gradients calculated at the surface of the wormhole while it developed compared to the critical pressure gradient for sand production predicted by Bratli and Risnes (1981).     

Mathematical Modeling of Slurry Infiltration and Particle Dispersion in Saturated Sand

This paper proposes a new computational method for the analysis of slurry infiltration in saturated sand considering the relationship among soil deformation, slurry seepage and particle dispersion. The nonlinear governing equations for slurry infiltration are derived, and the corresponding variational principles based on time increment are established. The finite element method is employed to solve the problem. The computational results are validated with the reported test data, which shows that this method is much better than the traditional Herzig method in predicting the particle deposition. The proposed method is demonstrated through an example of slurry infiltration in slurry trench.     

Mathematical Modeling of Two-Phase Convective Flows with Fine Particles

A two-phase convective flow with convection caused by a nonuniform distribution of solid particles is considered. The use of the mathematical model proposed is illustrated by an example of a two-phase flow in a shutter sedimentation reservoir.     

Thermoelasticity of bodies with microstructure and microtemperatures

This paper is concerned with a linear theory of thermodynamics for elastic materials with microstructure, whose microelements possess microtemperatures. It is shown that there exists the coupling of microrotation vector field with the microtemperatures even for isotropic bodies. Uniqueness and continuous dependence results are presented. The theory is used to establish the solution corresponding to a concentrated heat source acting in an unbounded continuum.     

A Class of Three-Dimensional Boundary-Value Problems of Thermoelasticity

Consideration is given to a class of static boundary-value problems of thermoelasticity and their solutions for bodies bounded by surfaces in orthogonal curvilinear coordinates. The following parameters are given: heat intensity, normal displacement, the tangential component of the curl of the displacement vector or temperature, the divergence of the displacement vector, and tangential displacement. The problem is reduced to the successive integration of the Laplace and Poisson equations with the classical boundary conditions. Specific problems of thermoelasticity are solved in Cartesian and cylindrical coordinates __________ Translated from Prikladnaya Mekhanika, Vol. 41, No. 9, pp. 137–144, September 2005.     

Constitutive Relations of Nonlinear Thermoelasticity of Anisotropic Bodies

Quasilinear relations for finite reversible deformation of anisotropic materials are obtained using a thermomechanical approach. Free energy is written as a function of temperature and compatible invariants of the logarithmic strain measure and basis tensors. Nonlinear thermomechanical effects including different types of material behavior in tension and compression and the temperature dependence of the elastic tensor are taken into account.     

Mathematical Modeling for One New Method of Breaking Ice Cover

The spatial problem of determining the stress-strain state of an ice plate of finite thickness broken by a patented method is solved using the theory of small elastoplastic strains and a proven numerical method. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 2, pp. 139–146, March–April, 2006.     

Thermoelasticity of orthotropic composites with ellipsoidal inclusions

Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Prikladnaya Mekhanika, Vol. 26, No. 9, pp. 3–10, September, 1990.     

Gas Sorption and the Consequent Volumetric and Permeability Change of Coal II: Numerical Modeling

The permeability of coalbed methane reservoirs may evolve during the recovery of methane and injection of gas, due to the change of effective stress and gas adsorption and desorption. Experimental and numerical studies were conducted to investigate the sorption-induced permeability change of coal. This paper presents the numerical modeling part of the work. It was found that adsorption of pure gases on coal was well represented by parametric adsorption isotherm models in the literature. Based on the experimental data of this study, adsorption of pure \(\hbox {N}_2\) was modeled using the Langmuir equation, and adsorption of pure \(\hbox {CO}_2\) was well represented by the N-Layer BET equation. For the modeling of CO \(_2\) & N \(_2\) binary mixture adsorption, the ideal adsorbed solution (IAS) model and the real adsorbed solution (RAS) model were used. The IAS model estimated the total amount of mixture adsorption and the composition of the adsorbed phase based on the pure adsorption isotherms. The estimated total adsorption and adsorbed-phase composition were very different from the experimental results, indicating nonideality of the CO \(_2\) –N \(_2\) –Coal-adsorption system. The measured sorption-induced strain was linearly proportional to the total amount of adsorption despite the species of the adsorbed gas. Permeability reduction followed a linear correlation with the volumetric strain with the adsorption of pure \(\hbox {N}_2\) and the tested CO \(_2\) & N \(_2\) binary mixtures, and an exponential correlation with the adsorption of pure \(\hbox {CO}_2\) .     

Spatial Stability for the Quasi-static Problem of Thermoelasticity

This paper is concerned with the quasi-static problem of thermoelasticity. The classical system of equations of thermoelasticity is a coupling of an elliptic equation with a parabolic equation. It poses some new mathematical difficulties. Here we study the exponential spatial decay of solutions. An upper bound for the amplitude in terms of the boundary and initial conditions is obtained. The extension of the spatial stability results to thermoelasticity of type III is also treated. Dedicated to C.O. Horgan on the occasion of his 60th birthdayMathematics Subject Classifications (2000) 74F05, 74G50.     

Mathematical Modeling of Flows Inside Rotating Bodies Made of Cellular-Porous Materials

A physicomathematical model is developed, which describes gas flows inside rapidly rotating bodies made of cellular-porous materials. Asymptotic and numerical solutions are obtained for some problems of forced centrifugal convection inside cylindrical cellular-porous bodies. The effect of the governing parameters (drag coefficient and dimensionless length of the cylinder) on characteristics and types of flows is considered. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 6, pp. 78–85, November–December, 2005.