Figures & data
Figure 1. (a) The Kelvin-Helmholtz instability [Citation7]; (b) from left to right, viscous, gravitational and inertial coiling respectively [Citation8]; (c) the Rayleigh–Taylor instability [Citation9]; (d) wine tears [Citation10]; (e) and (f) immiscible [Citation11] and miscible [Citation12] viscous fingering, respectively.
![Figure 1. (a) The Kelvin-Helmholtz instability [Citation7]; (b) from left to right, viscous, gravitational and inertial coiling respectively [Citation8]; (c) the Rayleigh–Taylor instability [Citation9]; (d) wine tears [Citation10]; (e) and (f) immiscible [Citation11] and miscible [Citation12] viscous fingering, respectively.](/cms/asset/0ed93754-dfc6-4463-a407-9d986aed6b30/tapx_a_2370838_f0001_oc.jpg)
Figure 2. Viscous fingering in Hele-Shaw cell with a planar channel geometry (a) and radial geometry (b).
![Figure 2. Viscous fingering in Hele-Shaw cell with a planar channel geometry (a) and radial geometry (b).](/cms/asset/12bf7435-00a3-420a-a007-4e77542e6d2a/tapx_a_2370838_f0002_oc.jpg)
Figure 3. Oil recovery during the secondary and tertiary phases without and with the presence of viscous fingering (a comparison of displacement front stability). Adapted from [Citation69].
![Figure 3. Oil recovery during the secondary and tertiary phases without and with the presence of viscous fingering (a comparison of displacement front stability). Adapted from [Citation69].](/cms/asset/16506418-acd3-4969-a6a8-811e8411e611/tapx_a_2370838_f0003_oc.jpg)
Figure 4. MR (Magnetic resonance) signal intensity with flow rate 0.03 ml/min, pressure 6MPa and temperature 295 K shows the displacement process in quartz glass sands BZ-02. The CO2 distribution is uneven prior to breakthrough, however, the displacement achieves a balance after some time, thus stabilizing the water and CO2 distribution [Citation78].
![Figure 4. MR (Magnetic resonance) signal intensity with flow rate 0.03 ml/min, pressure 6MPa and temperature 295 K shows the displacement process in quartz glass sands BZ-02. The CO2 distribution is uneven prior to breakthrough, however, the displacement achieves a balance after some time, thus stabilizing the water and CO2 distribution [Citation78].](/cms/asset/fa7cacbc-f7e9-48b0-bf60-c069dad1a317/tapx_a_2370838_f0004_oc.jpg)
Figure 5. Model of growing tumour and invading neighbouring tissue; Adapted from [Citation87].
![Figure 5. Model of growing tumour and invading neighbouring tissue; Adapted from [Citation87].](/cms/asset/745dbb1a-011a-4eba-af9a-8513a765000a/tapx_a_2370838_f0005_oc.jpg)
Figure 6. Cross sections of the flat convergent (a) and divergent (b) Hele-Shaw cells [Citation106]; Spherical (c) and conical (d) Hele-Shaw cell. Adapted from [Citation107].
![Figure 6. Cross sections of the flat convergent (a) and divergent (b) Hele-Shaw cells [Citation106]; Spherical (c) and conical (d) Hele-Shaw cell. Adapted from [Citation107].](/cms/asset/2a06af7e-dfbd-4178-b67d-0b63213bbf57/tapx_a_2370838_f0006_oc.jpg)
Figure 8. Expanding air bubble displacing the fluid between the plates (left) and velocity profile (right).
![Figure 8. Expanding air bubble displacing the fluid between the plates (left) and velocity profile (right).](/cms/asset/d3f751c8-b010-4b34-afdf-75ec6d36217e/tapx_a_2370838_f0008_oc.jpg)
Figure 9. A perturbed interface in a radial flat rigid wall Hele-Shaw cell; Adapted from [Citation119].
![Figure 9. A perturbed interface in a radial flat rigid wall Hele-Shaw cell; Adapted from [Citation119].](/cms/asset/2654f5d7-25c3-4aac-a389-6ff8354dbe64/tapx_a_2370838_f0009_oc.jpg)
Figure 10. A complex bifurcation pattern of viscous fingering simulated by the DLA model; the patterns’ ages are indicated by their colours, with the first generated region being blue and the newly formed being red [Citation132].
![Figure 10. A complex bifurcation pattern of viscous fingering simulated by the DLA model; the patterns’ ages are indicated by their colours, with the first generated region being blue and the newly formed being red [Citation132].](/cms/asset/4a4a0168-fc2d-46a1-b111-f27aec70d975/tapx_a_2370838_f0010_oc.jpg)
Figure 11. Schematic diagram of an elasto-rigid Hele-Shaw cell: a narrow gap between a rigid horizontal top plate and an elastomer confined within a rigid mould (left); fluid injected into the compliant Hele-Shaw cell at a constant flow rate spreads outwards, with a radial front position , deforming the elastomer and displacing fluid resident in the cell; Adapted from [Citation168].
![Figure 11. Schematic diagram of an elasto-rigid Hele-Shaw cell: a narrow gap between a rigid horizontal top plate and an elastomer confined within a rigid mould (left); fluid injected into the compliant Hele-Shaw cell at a constant flow rate spreads outwards, with a radial front position rf, deforming the elastomer and displacing fluid resident in the cell; Adapted from [Citation168].](/cms/asset/c09bd6fa-1844-4359-989c-55274215f8a5/tapx_a_2370838_f0011_oc.jpg)
Hydrodynamically unstable displacement () can be stabilized by electrokinetic control; an electro-osmotic flow can be stabilized by a positive current (electrokinetic thinning), however, a negative current of the same magnitude makes the displacement front unstable, resulting in the finger patter of smaller wavelengths [Citation175].
![Hydrodynamically unstable displacement (M<1) can be stabilized by electrokinetic control; an electro-osmotic flow can be stabilized by a positive current (electrokinetic thinning), however, a negative current of the same magnitude makes the displacement front unstable, resulting in the finger patter of smaller wavelengths [Citation175].](/cms/asset/6fb6b831-05f3-4d91-b478-b62b907d4572/tapx_a_2370838_f0012_oc.jpg)