Concentration field in traveling-wave and stationary convection in fluid mixtures

Bistability of Slow and Fast Traveling Waves in Fluid Mixtures

“…The structural changes that occur with growing χ can be observed experimentally in topview and even better in sideview shadowgraph intensity distributions [20,10,12]. The sideviews in Fig.…”

“…The convective amplitude of the fast (slow) TW is small (large) while the amplitude of its concentration contrast is large (small). The fast stable TWs have so far remained unnoticed in experiments [4][5][6][7][8][9][10][11][12][13] and numerical simulations [14,15]. They develop with increasing Soret coupling via a saddle node bifurcation out of a dent in the subcritically bifurcating unstable TW branch.…”

“…This coupling chain causes a surprising richness of spatiotemporal pattern formation [3] even close to the onset of convection. In particular there are convective structures [2][3][4][5][6][7][8][9][10][11][12][13][14][15] consisting of coupled traveling waves (TWs) of velocity, temperature, and concentration with significantly different shapes [14,15]. Since nonlinear concentration advection is typically much larger than linear diffusion -the ratio of these two transport rates can easily be above 1000 -it is not surprising that these TW states are typically strongly nonlinear.…”

“…1 at ψ = −0.25. The significance of such a dent on the lower unstable branch of solutions being unaccessible to experiments [4][5][6][7][8][9][10][11][12][13] as well as to earlier numerical simulations [14,15] has not been appreciated appropriately although it can be seen in the paper of Bensimon et al [21] in the limit of small Soret coupling and σ → ∞. With our new finite difference method and our many mode Galerkin scheme we can now trace out the complete solution branch and determine how its bifurcation topology changes with ψ. Sideview shadowgraph intensity distributions obtained as described in [10,15] from the numerically determined TW states that are marked by the respective triangles in Fig.…”

Roll convection of binary fluid mixtures in porous media

“…Especially, if the binary mixture shows a non-vanishing Soret effect, i.e., if concentration currents are driven by temperature gradients, the dynamics of the system are expected to change due to a coupling of the temperature field into the concentration field. For the classical Rayleigh-Bénard system without porous medium, there has been a large body of work dealing with binary mixtures under the influence of the Soret effect (Eaton et al (1991); Barten et al (1995); Huke. & Lücke (2002); Le Gal et al (1985); Dominguez-Lerma et al (1995); Barten et al (1989); Schöpf & Zimmermann (1993); Knobloch & Moore (1988); Cross & Kim (1988); Kolodner et al (1986); Fütterer & Lücke (2002); Touiri et al (1996); Ahlers & Rehberg (1986); Walden et al (1985)).…”