Showing papers on "Mixture theory published in 1985"

Lagrangean Continuum Theory for Saturated Porous Media

Abstract: A theory for a two phase material based on the concepts of the theory of mixtures is developed in a Lagrangean reference frame. This theory may be applied for the analysis of flow of water through saturated soils. For this purpose, a new law for the flow of water through porous media is postulated. The material behavior of the soil skeleton is modeled as an elastoplastic, time independent porous solid. The material is assumed to be initially isotropic.

A review of mixture theory with applications in physical oceanography and meteorology

Abstract: The motivation for this paper is the observation that most problems in physical oceanography and meteorology are concerned with mixtures of two or more constituents. Some diverse examples include seawater, turbidity currents, deforming seabeds containing pore fluids, and air containing all phases of water. In the last 15 years a revolution has occurred in the theoretical continuum approach to mixtures; however, none of this has found its way into the oceanographic or meteorological literature. Thus it is appropriate to compare models arising from this modern approach with the classical results. The major distinction between the two approaches is that the modern theory stipulates equations of motion for each constituent, whereas in the classical result it is assumed that the equations of motion for the mixture suffice for a description of the dynamics. The ramifications of this are explored in several diverse areas in oceanography and meteorology. It is shown that for the hydrothermal-dynamic description of seawater for purely dynamical purposes the distinction is not important. It is not as clear that this is true for models of fine and microscale processes. The principal difficulty seems to be the parameterization of mixing by Fickian-type diffusion. Mixture theory provides an alternative that, for special situations, reduces to the Telegraph equation. For models of ocean seabed interactions it seems clear that the modern theory should be utilized. In this regard, some general dynamical models for sediment transport and turbidity currents and viscous porous seabeds are developed. Also, the thermodynamics of a mixture of ice, water vapor, and condensate in the atmosphere is treated from the standpoint of the modern theory.

Development of Advanced Constitutive Models for Plain and Reinforced Concrete.

Abstract: : The objective of the research is to develop a new and advanced approach to modeling the constitutive behavior of reinforced concrete that provides substantial improvement over existing approaches, especially in the nonlinear response regime. To accomplish this, the research has been partitioned into two major tasks, which are being pursued concurrently. One task consists of formulating a procedure (mixture theory) for analytically mixing reinforcing steel and plain concrete, so that the interaction between the two is properly modeled. The other task consists of developing a model of plain concrete, which accurately portrays its nonlinear, multiaxial behavior and is also computationally feasible for use in conjunction with the mixture theory. The mixture theory is designed to synthesize the global constitutive properties of reinforced concrete from the properties of plain concrete, steel, interfaces and reinforced geometry. The progress made during the first year's effort toward achieving these objectives is described.