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DY: Dynamik und Statistische Physik
DY 46: Poster
DY 46.48: Poster
Donnerstag, 29. März 2001, 15:45–18:15, Foyer S\ 3
Buoyantly driven instability of reaction fronts in Hele-Shaw cells and porous media — •Martin Böckmann1,2, Jérôme Martin2, Nicole Rakotomalala2, Dominique Salin2, and Stefan C. Müller1 — 1Institut für Experimentelle Physik, Universität Magdeburg, Universitätsplatz 2, 39108 Magdeburg — 2Laboratoire F.A.S.T., Bât. 502, Campus Universitaire, 91405 Orsay, France
Due to gravity, fronts of autocatalytic reactions which produce a local density increase may become unstable and develop a Rayleigh-Taylor-like convection. In a quasi-2D cell, the flow deforms an ascending front into a pattern of upward bubbles and downward spikes. In a porous medium, a convective deformation of the front can also be distinguished from roughening due to the spatial inhomogeneity.
We measured the growth rates depending on the wave number k by means of a Fourier transform, and find instability only below a critical k0 and a stabilisation for higher wave numbers. So far, this stabilization of small scales has been explained by the curvature dependence of the propagation velocity. However, a better quantitative agreement was now achieved by considering dispersion of a miscible fluid interface. Furthermore, we characterize the finger selection processes by means of the position of the maxima and by the growth speed of different fingers.