Browsing by Author "Lee, Young Hoon"

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    Immiscible Radial Newtonian and non-Newtonian Flow Displacements in Porous Media
    (2019-09-12) Lee, Young Hoon; Azaiez, Jalel; Gates, Ian Donald; Chen, Zhangxing; Nowicki, Edwin P.
    Immiscible flows that involve radial displacements of shear-thinning or shear-thickening fluids by a Newtonian fluid in a homogeneous porous medium, are modeled numerically. The interfacial instabilities are tracked in time for different values of the rheological parameters, namely the Deborah number (De) and the power-law index (n) and are characterized through the effective number of fingers and the finger area density. The results of the study reveal that the effects of these two parameters on the instability are not monotonic, and it is found that the flow is least unstable for some critical value of either De or n. The dependence of these critical values in particular on the mobility ratio (M) and Capillary number (Ca) is analyzed. It is found that when all other parameters are fixed, the critical Deborah number (Dec) increases as the power-law index increases in shear-thinning fluids or decreases in shear-thickening ones. Similarly, the critical power-law index (nc) increases with increasing (decreasing) Deborah number in shear-thinning (shear-thickening) flows. Furthermore, both critical parameters are found to vary monotonically with the mobility ratio, with the dependence most noticeable at small values of M. Their variation with the Capillary number is however non-monotonic reaching an extremum at an intermediate value of Ca. An examination of the rate of shear strain at the interface reveals that it consistently shows the smoothest variation and smallest average value at the critical parameter. In addition to non-Newtonian flow displacements, immiscible radial displacement flows between two Newtonian fluids in a non-homogeneous porous media are also examined numerically. The non-homogeneous porous medium is modeled to vary periodically in the radial direction. Simulations are performed for different values of the Capillary number (Ca) and the mobility ratio (M) varying the frequency of the periodic permeability. The results show that the periodic permeability has negligible effects on the finger structures when the Capillary number and the mobility ratio are small. However, the instability of an interface can be noticeably enhanced in a higher frequency periodic permeability field when the Capillary number and the mobility ratio are large enough.
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    Viscous Fingering Instability of Complex Fluids in a Radial Hele-Shaw Cell
    (2024-03-15) Lee, Young Hoon; Gates, Ian Donald; Azaiez, Jalel; Lu, Qingye Gemma; Hejazi, Hossein; Li, Sunny Ri
    When a less-viscous fluid displaces another fluid of higher viscosity in a porous medium, instability can develop at the interface between the two fluids. The instability manifests itself in the form of finger-like patterns of the displacing fluid propagating through the displaced one. In this work, viscous fingering instabilities involving complex fluids in a radial Hele-Shaw is investigated. Many fluids in our lives such as shaving foams, glues, flour-water dough, mayonnaise, and paints are complex fluids which exhibit multiple non-Newtonian properties simultaneously such as shear-thinning or shear-thickening, yield stress, and viscoelastic effects. First, the effects of normal stress differences of dilute low molecular weight poly(ethylene oxide) (PEO) solutions on viscous fingering instability are studied. Second, we investigate the instabilities associated with air invading foam in Hele-Shaw cell. Third, we examine the effects of water in viscous fingering instabilities of air displacing mineral oil. Fourth, the instability at the interface between two parallel flows of immiscible liquids through a uniform planar pore is studied by using linear stability analysis. We pose important questions: How does normal stresses affect immiscible radial viscous fingering? How does fingering occur into foam? Is it similar to that of a single-phase liquid? The experimental observations reveal nonmonotonic and opposing effects are evident depending on the molecular weight of the PEO and the stage of the radial viscous fingering evolution. We have identified three different flow regimes in the immiscible radial displacement flows of air invading foam in Hele-Shaw cell. The presence of a small volume of water leads to significantly different fingering patterns than that when no water is present. The outcomes are significant because the results demonstrate new behaviors for displacement flow of complex fluids.