Controlling viscous fingering with fluid-structure interactions

Lead Research Organisation: University of Oxford
Department Name: Engineering Science


Viscous fingering is a classical hydrodynamic instability that occurs when a fluid is injected into a porous medium or Hele-Shaw cell that already contains a more viscous fluid. The result is that the invading fluid will propagate through the defending fluid in narrow, finger-like channels rather than displacing it uniformly. As with most instabilities, viscous fingering can be desirable or undesirable---For example, it has a strong and adverse impact on enhanced oil recovery and many manufacturing processes, but it can also be exploited to promote mixing in microfluidic devices. In these and other applications, it would be extremely useful to be able to suppress, enhance, or otherwise control this phenomenon.

The prospect of controlling hydrodynamic instabilities such as viscous fingering is a long-standing challenge across engineering. One promising approach for achieving this is by manipulating the flow with a moveable or deformable solid structure. Most previous efforts to control instabilities via such fluid-structure interactions (FSI) have been directed at inertial flows (e.g., aerodynamic drag and turbulence), but this idea also has clear relevance to viscous flows (e.g., in microfluidics, biomedical engineering, and subsurface flow), including viscous fingering.

The goal of this project is to strengthen and broaden our understanding of the impact of FSI on viscous flows in general, and on viscous fingering in particular. We will first develop a novel apparatus for measuring and controlling the impact of FSI on viscous flow in a Hele-Shaw cell. Then, by combining high-resolution experiments in this system with mathematical modelling, we will develop a new strategy for controlling viscous fingering. This strategy for enhancing or suppressing viscous fingering can then be applied to a wide variety of practical challenges, from microfluidics to enhanced oil recovery.

Planned Impact

The primary outputs of this project will be high-resolution experimental images/videos of viscous fingering in several different flow-cell configurations, models and modelling results, and novel strategies for controlling viscous fingering through the manipulation of volumetric confinement. In addition to fundamental new insight into the impact of FSI on viscous instabilities, we expect this project to spur further interest in this relatively unstudied research area and to help us develop stronger connections with the oil and gas industry.

We expect that our results will spur strong interest in the idea of controlling viscous fingering in a deformable porous medium, which would be of particular relevance to the oil industry and in the design of microfluidic systems. We will work closely with industry leaders during the project to explore these connections (see letters from Total E&P and Schlumberger). The results may also lead to the design of novel valve technology.

In order to achieve the maximum impact on academic and industrial research, we will make our data and models freely available via a dedicated page on our website, and we will advertise the availability of these tools in papers and at conferences. Images and videos of viscous fingering have proven to be very effective tools for generating interest in and enthusiasm for engineering and the physical sciences. We will post videos on our website and make them freely available for public outreach. We expect that they will also be a valuable teaching tool. We will also organise a workshop at Oxford on the coupling of hydrodynamic instabilities with FSI, inviting relevant experts from academia and industry.

Our work will also inform the development of a new coursework module on viscous flows for 2nd year students in our department, in which flow in Hele-Shaw cells will play a key part. This will be an opportunity for the PDRA to gain valuable teaching experience.


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Description Viscous fingering is a classical hydrodynamic instability that occurs when a low-viscosity invading fluid is used to push a high-viscosity defending fluid through a porous medium or a Hele-Shaw cell (a thin gap between two plates). The result is that the invading invading fluid will propagate through the defending fluid in narrow, finger-like channels rather than displacing it uniformly. Previous research has shown that this displacement process is much more efficient (viscous fingering is suppressed) in highly deformable Hele-Shaw cells, where the fluid pressure dramatically increases the gap thickness by inflating the flow cell as the fluids advance.

In this project, we have studied this phenomenon in deformable but confined systems, where the total volume of the flow cell must be conserved. To do this, we developed a novel apparatus for measuring and controlling the impact of deformability on viscous flow in a Hele-Shaw cell. Using this apparatus, we showed that deformability has a much more nuanced interaction with viscous fingering in confined systems; it alters the fingering pattern, but does not necessarily suppress fingering. This suggests that the degree of deformability and confinement could be selected together to produce a particular type of fingering pattern.
Exploitation Route With further development, our results could be used as the basis for new techniques in enhanced oil recovery or contaminant remediation (to increase recovery efficiency) or in microfluidic devices or manufacturing processes (to enhance or suppress mixing). Our results will also inspire further research into the impact of fluid-structure interactions on viscous flows and instabilities; we have shown that this impact is more nuanced than previously thought.
Sectors Energy,Environment,Manufacturing, including Industrial Biotechology,Other

Description Deformation control on flow and transport in soft porous media
Amount € 1,482,862 (EUR)
Funding ID 805469 
Organisation European Research Council (ERC) 
Sector Public
Country European Union (EU)
Start 02/2019 
End 01/2024