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Title: Investigation of smooth contact angle treatment in porous media
Author: Burel, Thomas
ISNI:       0000 0004 7657 166X
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2018
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Some of the key challenges faced in the oil/gas extraction and carbon dioxide injection/storage processes are the presence of complex geometries and the significant effect of the capillary forces which arise at low capillary numbers. Therefore, the contact angle needs to be carefully treated. Mesoscopic techniques such as lattice Boltzmann methods are capable of dealing with lower capillary numbers as compared to the Navier-Stokes solvers, which can also implicitly capture the interface between two fluids. To investigate immiscible two-phase ows at low Reynolds and capillary numbers (Re < 1 and Ca < 1), the colour-fluid model is used i.e. the Rothman-Keller model [1]. This model includes two steps: a perturbation operator from Lishchuk et al [2] (the continuum surface force [3]) or Gunstensen et al [4] approaches and a recolouring operator [5]. However, the lattice Boltzmann implementation employs a Cartesian grid for domain discretisation that is unable to conform with curved surfaces. It misinterprets those curved surfaces as a series of stair-like patterns. On those surfaces, a non-physical contact angle could be defined which may lead to a numerically flooding of the wetting fluid inside the droplet for a non-spreading drop or outside for a spreading droplet. To remove this unphysical behaviour and take into account the flow field effect on the contact angle, interpolation techniques are employed to estimate the real contact angle on the 'stairs' boundaries. We also employ extrapolations to obtain more accurate density on concave corners, thus the grid resolution can be reduced. After the code is numerically validated on static droplets, on droplets deformed under a simple shear, and on simple geometries. Finally, we perform simulations on a Berea sandstone sample [6] to understand dynamics behaviour of immiscible fluids in porous media.
Supervisor: Zhang, Yonghao Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral