Asger Johannes Skjøde Bolet

A thesis for the degree of Doctor of Philosophy defended Áugust 2018.

The PhD School of Science, Faculty of Science, Biocomplexity, Niels Bohr Institute, University of Copenhagen

Academic advisor:
Joachim Mathiesen

Electrohydrodynamics in one and two phases

Transport of electrolytes in rock–formations, where the fluid paths are on the scale of micrometers down to nanometers, are common in geology. If the rock–electrolyte interface is charged, the effect on flow–permeability can be rather dramatic on such a small scale due to the electric double layer. Good theoretical and numerical studies of such effects have been rather limited because of strong non-linearities of the governing equations, which are even difficult to handle in simple geometries. However, in this work we present a numerical study of geometrical effects on electrohydrodynamic flow in a model fracture, a channel with sinusoidal varying depths. The simulations suggest that electrohydrodynamics leads to increased channeling of the flow which might be of importance in rock precipitation and dissolution. Furthermore, electrolytes can also play a key role in two-phase flow as it can change the wetting properties on a macroscopic scale, leading to vastly different transport properties. Such electrowetting effects are present near charged rock–fluid–interfaces and play a vital role in settings where two immiscible fluids coexist in a porous media. To study such phenomena in pore–like geometries we have performed a numerical study of two–phase electrohydrodynamics. In these simulations we have seen clear evidence that the release of an electric–inert fluid from a harged pore can be driven by electric–interactions between the pore-wall and the ions of electrolyte.