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EXPERIMENTAL STUDY OF THE GEOMETRIC CHARACTERISTICS OF BUBBLES/DROPLETS PASSING THROUGH A PORE SPACE
- Author / Creator
- Shadi Ansari
The multi-phase flow motion of droplets and bubbles through porous media has been reported for different applications. The importance of the effect of the presence of emulsions on the performance of steam-assisted gravity drainage (SAGD) for oil extraction is discussed as a relevant process. SAGD models of these flow conditions have a major limitation by commonly adopting the single-phase flow assumption in their analyses. Researchers have reported the likelihood of the emulsification processes to prevail at SAGD conditions. The issue has been addressed in a limited number of works that demonstrated a modeling improvement by applying a multi-phase assumption. The pore-scale interactions of the multi-phase flow in a porous region is a complex phenomenon that needs to be studied in detail.
The difference between the mobility of the phases and the presence of interfacial forces acting on the interface lead to various flow characteristics. The development of a methodology to evaluate multi-phase flow motion and investigation of the interaction of multi-phase flow passing through pore geometries is outlined in detail. A theoretical model used to evaluate the motion of an isolated dispersed phase, a bubble, in a confined geometry showed that the pressure difference between the leading and the trailing edge describes the motion of an isolated dispersed phase and required energy to mobilized trapped phases. An indirect pressure measurement technique to calculate the pressure field of a multi-phase flow in the porous media using non-intrusive velocity measurement was introduced and discussed in detail. Using the proposed method, the effect of discontinuous phase size and the flow rate of the continuous flow on the pressure was investigated. The importance of the phase pinning phenomenon was also considered in the motion of the flow.
The developed method for measurement of the pressure of the dispersed phase was also applied to a refractive index-matched dispersed phase, a droplet, to expand its capability. Pore-scale velocity measurements were achieved using microparticle shadow velocimetry (µ-PSV). By detailed measurement of velocity and applying theoretical relations that suit the flow field under study, the resultant pressure field was determined. The results of the velocity measurement of the continuous phase were used to determine the pressure field calculated from a simplified Navier-Stokes expression of the flow, discretized using an Eulerian approach. The pressure determined from the shape analysis technique and the velocity measurements were also compared to validate the results.
The interaction of between the dispersed phase and also the confined solid geometry was studied using the proposed method. In this part of the study, pore geometries having different surface roughness and confined shapes were considered. The results of the study showed that phase pinning intensifies as the roughness of the pore structure increases. The higher number of pinning events in the motion of a dispersed phase results in an increase in the transit time required for the flow passage. Larger bubbles also had a longer transit time through a pore structure due to higher deformation.
The interaction of the dispersed phases in a loosely packed bubbly flow was studied using different arrangements of the array and matrix of the bubble flow entering a pore geometry. Bubbles in both arrangements experience deformation as they pass through the pore structure. The bubbles decelerate before they reach the pore and accelerate as they pass through the pore throat due to the deformation of the phase. The motion of the bubble entering the pore in the matrix arrangement leads to a temporary repelling of the competing bubble from the pore. In this condition, the bubbles decelerate further as they get closer to the pore due to the competition to enter the pore geometry.
This study makes a major contribution to research on multi-phase flow through porous region by providing analytical and experimental insights on the pore scale interaction and accounting for three-phase contact line pinning. The results of the study indicated that the size of the dispersed phase, flow rate of the continuous phase and solid interface properties are the factors effecting the required transit time of the phase passage and the energy to mobilize trapped phases.
- Graduation date
- Fall 2021
- Type of Item
- Doctor of Philosophy
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