2 research outputs found
Precipitation induced filament pattern of injected fluid controlled by structured cell
Mixing of two fluids can lead to the formation of precipitation. If one of
the fluids is injected into a confined space filled with the other, a created
precipitate disrupts the flow locally and intricates complex spatiotemporal
patterns. Here, we show that such injection patterns can be controlled
consistently by injection rate and obstacles. Our experimental results revealed
filament patterns for high injection and low reaction rates, and the injection
rate can control the number of active filaments. Furthermore, appropriately
spaced obstacles in the cells can straighten the motion of the advancing tip of
the filament. A mathematical model based on a moving boundary adopting the
effect of precipitation reproduced the phase diagram and the straight motion of
filaments in structured cells.Comment: 10 pages, 10 figure
Extensive tip-splitting of injected organic liquid into an aqueous viscoelastic fluid
The injection of a fluid into another fluid causes a spatiotemporal pattern along the injection front. Viscous fingering is a well-known example when the replaced material is a viscous fluid. Notably, most fluids are, in reality, viscoelastic, i.e., they behave as an elastic solid over short timescales. For this reason, it is important to study the situation when the replaced fluid is viscoelastic. In this study, we observed a dynamics of fluids when an incompressible organic liquid was injected into an oleophilic Hele–Shaw cell filled with an aqueous viscoelastic fluid made of a wormlike micellar solution. We found extensive tip splitting of the injection front, which led to thin fingers with a characteristic size comparable to four times the cell thickness. We examined the material properties and suggest that the thin fingering pattern observed in our system is due to the delamination of viscoelastic fluid from the bottom substrate surface. Our result shows that the effect of interfacial energy in the existing solid layer should be considered in the injection process