Showing papers on "Shell balance published in 1991"

Displacement of a Newtonian fluid by a non-Newtonian fluid in a porous medium

Abstract: This paper presents an analytical Buckley-Leverett-type solution for one-dimensibnal immiscible displacement of a Newtonian fluid by a non-Newtonian fluid in porous media. The non-Newtonian fluid viscosity is assumed to be a function of the flow potential gradient and the non-Newtonian phase saturation. To apply this method to field problems a practical procedure has been developed which is based on the analytical solution and is similar to the graphic technique of Welge. Our solution can be regarded as an extension of the Buckley-Leverett method to Non-Newtonian fluids. The analytical result reveals how the saturation profile and the displacement efficiency are controlled not only by the relative permeabilities, as in the Buckley-Leverett solution, but also by the inherent complexities of the non-Newtonian fluid. Two examples of the application of the solution are given. One application is the verification of a numerical model, which has been developed for simulation of flow of immiscible non-Newtonian and Newtonian fluids in porous media. Excellent agreement between the numerical and analytical results has been obtained using a power-law non-Newtonian fluid. Another application is to examine the effects of non-Newtonian behavior on immiscible displacement of a Newtonian fluid by a power-law non-Newtonian fluid.

Hydrodynamics of Rapid Shell Closure in Articulate Brachiopods

Abstract: The rapid shell-closing mechanism in articulate (hinged) brachiopods is subject to important hydrodynamic constraints related to expulsion of water from the shell. Fluid forces influence, for example, the speeds of shell closure and the mass flux rates of water from the shell. The principal hydrodynamic forces acting on a shell during rapid closure are (1) inertial reactions, due to the acceleration of water (=acceleration reaction), and (2) water pressure forces which develop as water is expelled from the shell. A generalized hydrodynamic model describes the relative magnitudes of the acceleration and pressure forces as functions of the shell9s angular acceleration, velocity and gape. In general, the acceleration reaction dominates the kinematics of shell closure during the initial phases of a closing event, whereas pressure forces dominate towards the later phases of shell closure. Solutions of the general model predict how variables such as the closing speed and the mass flux of water depend on shell size, initial shell gape and on the magnitude of the closing force. Results indicate that inertial reactions (due to acceleration of water) dominate the mechanics of shell closure in articulate brachiopod taxa.