Silica suspensions fingering

Viscous Fingering of Silica Suspensions Dispersed in Polymer Fluids... 

Figure 5. Typical fingering patterns for PPG as well as the 2.5 and 7.5 wt % silica suspensions dispersed in PPG at the injection pressure of 6.0 kPa from...

In order to study the onset of the Saffman-Taylor instability for the PPG-silica suspensions, we estimated the imposed shear rate 2v/b at which the unstable finger for the first time appears. The 2v/b values are obtained as 72, 30, 17, and 11 s for the 2.5, 5.0, 7.5, and 10.0 wt% PPG-silica suspensions, respectively and they are independent of the injection pressure. Moreover, these values are close to the critical shear rates of the corresponding PPG-silica... 

The relative finger width A is well known related to the dimensionless parameter 7/5=12 rfeffv/y) (W/bf (75,79), where yis the surface tension of the displaced fluid. At the present time the surface tensions of the silica suspensions are not available and the values of A are plotted as a function of 7/5 12 (rjeffVt) (W/bf in Figure 7. The A value of PPG gradually decreases and tends to approach to a plateau value of ca. 0.5 at higher l/B value. The A values of the 2.5 and 5.0 wt % PPG-silica suspensions also decrease with an increase with 7/5 and they are smaller than that of PPG at the higher 7/5... 

On the other hand, the v values of the 7.5 and 10.0 wt % silica suspensions are more negatively deviated from that predicted by the modified Darcy s law with an increase in the silica concentration. They tend to approach a plateau value with an increase in Vp, This means that the finger velocities of... 

Kawaguchi studied the problem of viscous fingering in silica suspensions in polymer solutions (44). Experiments in drop towers revealed that sedimentation of the silica particles affected slightly the tip-splitting instability. 

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