472999 Miscible, Unstable Viscous Fingering Patterns in a Radial Hele-Shaw Cell
The effect of flow rate, polymer concentration, and salt addition was also demonstrated. Dye tracer was mixed with the non-Newtonian fluid (Xanthan Gum (XG) T622, CP Kelco) before injection/withdrawal to capture images of resulting viscous fingering patterns when a less viscous fluid displaces a more viscous fluid (unstable case). The Hele-Shaw cell was constructed from two parallel smooth glass plates with an initial displacement of 5 mm. Shims were placed at the outer edge of the circular plate to create a variable aperture system for studying displacement and flow path selectivity. The effect of flow rate, polymer concentration, and salt addition was also demonstrated. Rheological characterization of guar gum (GG) and XG at various concentrations was also performed in order to constrain rheological behavior when it is used for future in-field measurements utilizing ground penetrating radar (GPR) to reveal aquifer system structure. These polymers were also characterized with the addition of salt, which is used as the conductive tracer for GPR, and low density glass bubbles for density adjustments. Rheological data for both GG and XG with and without salt additions will be presented, along with characterization and parameterization of unstable viscous fingering patterns. Guar gum was shown to have high error and poor experimental reproducibility while xanthan gum showed better reproducibility and optimal shear-thinning behavior.