Solution of two dimensional Stokes flow with elliptical coordinates and its application to permeability of porous media

Analytical developments of the biharmonic equation representing bi-dimensional Stokes flow are realized with elliptic coordinates. It's found that the streamfunction is expressed with series expansions based on Gegenbauer polynomials of first and second kinds with order one Cn1and Dn1. A term corresponding to order n=-1 is added in view to create drag on a body around which the fluid flows. Application to an array of elliptic cylinders is made and the permeability of this medium is determined as a function of porosity.

Prestack wave-equation depth migration in elliptical coordinates

We extend Riemannian wavefield extrapolation (RWE) to prestack migration using 2D elliptical-coordinate systems. The corresponding 2D elliptical extrapolation wavenumber introduces only an isotropic slowness model stretch to the single-square-root operator. This enables the use of existing Cartesian finite-difference extrapolators for propagating wavefields on elliptical meshes. A poststack migration example illustrates advantages of elliptical coordinates for imaging turning waves. A 2D imaging test using a velocity-benchmark data set demonstrates that the RWE prestack migration algorithm generates high-quality prestack migration images that are more accurate than those generated by Cartesian operators of the equivalent accuracy. Even in situations in which RWE geometries are used, a high-order implementation of the one-way extrapolator operator is required for accurate propagation and imaging. Elliptical-cylindrical and oblate-spheroidal geometries are potential extensions of the analytical approach to 3D RWE-coordinate systems.