Thomas Ramstad

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We study experimentally the case of steady-state simultaneous two-phase flow in a quasi-two-dimensional porous media. The dynamics is dominated by the interplay between a viscous pressure field from the wetting fluid and bubble transport of a less viscous, nonwetting phase. In contrast with more studied displacement front systems, steady-state flow is in(More)
We report on experimental studies of steady-state two-phase flow in a quasi-two-dimensional porous medium. The wetting and the nonwetting phases are injected simultaneously from alternating inlet points into a Hele-Shaw cell containing one layer of randomly distributed glass beads, initially saturated with wetting fluid. The high viscous wetting phase and(More)
A fast screening method for the determination of the dissociation constants (pKa) of acidic, basic, and multivalent compounds was developed by using pressure-assisted capillary electrophoresis (PACE). External air pressure was applied to shorten the analysis time. The separation efficiency decreases as air pressure increases. However, it was found that air(More)
Using numerical simulations, we study immiscible two-phase flow in a pore network reconstructed from Berea sandstone under flow conditions that are statistically invariant under translation. Under such conditions, the flow is a state function which is not dependent on initial conditions. We find a second-order phase transition resembling the phase inversion(More)
We study the scaling properties of the solid-on-solid front of the infinite cluster in two-dimensional gradient percolation. We show that such an object is self-affine with a Hurst exponent equal to 23 up to a cutoff length approximately g{-4/7}, where g is the gradient. Beyond this length scale, the front position has the character of uncorrelated noise.(More)
We report numerical studies of the cluster development of two-phase flow in a steady-state environment of porous media. This is done by including biperiodic boundary conditions in a two-dimensional flow simulator. Initial transients of wetting and nonwetting phases that evolve before steady state has occurred, undergo a crossover where every initial pattern(More)
We briefly review some important properties of superfluid flow, especially the problem of critical velocity. We then present new numerical simulation results for a mesoscopic model of superfluids shedding light on the free-energy landscape, the critical velocity and the formation of vortices, which destroy the superflow when the velocity is high.
When immiscible wetting and nonwetting fluids move in parallel in a porous medium, an instability may occur at sufficiently high capillary numbers so that interfaces between the fluids initially held in place by the porous medium are mobilized. A boundary zone containing bubbles of both fluids evolves, which has a well-defined thickness. This zone moves at(More)
We report on experimental and numerical studies of steady-state two-phase flow in a quasi twodimensional porous medium. Experimentally, the wetting and the non-wetting phase are injected simultaneously from alternating inlet points into a Hele-Shaw cell containing one layer of randomly distributed glass beads, initially saturated with wetting fluid.(More)