The linear stability of double-diffusive miscible rectilinear displacements in a Hele-Shaw cell

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We investigate the viscous instability of a miscible displacement process in a recti-linear geometry, when the viscosity contrast is controlled by two quantities whichdiuse at dierent rates. The analysis is applicable to displacement in a porousmedium with two dissolved species, or to displacement in a Hele-Shaw cell with twodissolved species or with one dissolved species and a thermal contrast. We carry outasymptotic analyses of the linear stability behaviour in two regimes: that of smallwavenumbers at intermediate times, and that of large times.An interesting feature of the large-time results is the existence of regimes in whichthe favoured wavenumber scales with t−1/4, as opposed to the t−3/8 scaling foundin other regimes including that of single-species ngering. We also show that theregion of parameter space in which the displacement is unstable grows with time,and that although overdamped growing perturbations are possible, these are neverthe fastest-growing perturbations so are unlikely to be observed. We also interpretour results physically in terms of the stabilising and destabilising mechanisms actingon an incipient nger.
Original languageEnglish
Pages (from-to)564-577
Number of pages14
JournalEuropean Journal of Mechanics - B/Fluids
Issue number4
Early online date5 Feb 2009
Publication statusPublished - Aug 2009


  • viscous fingering
  • instability
  • viscosity
  • Hele-Shaw cell

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