Perez-Garcia, C. (C.)
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- Bénard-Marangoni convection in square containers(American Physical Society, 1997) Perez-Garcia, C. (C.); Krmpotic, D. (D.); Mindlin, G.B. (G.B.)Convection in a square container of small aspect ratio is studied taking into account thermocapillarity as well as gravity effects. In addition to the geometrical symmetry (D4), the existence of hidden translational symmetries, due to boundary conditions, allows us to explain the qualitative features of the patterns found in recently reported experiments @T. Ondarzuhu et al., Phys. Rev. Lett. 70, 3892 ~1993!#. The nonlinear interaction between mixed modes and pure modes is shown to give rise to a sequence of bifurcations that leads to the onset of oscillations, as observed experimentally.
- Thermal properites in surface tension driven convection(American Physical Society, 1998) Perez-Garcia, C. (C.); Bestehorn, M. (M.); Echebarría, B. (Blas)We discuss the approximations that may be applied to the convective problem of a horizontal layer of liquid in contact with an air layer, both enclosed between conducting walls. Assuming that heat flows across the air mostly by conduction ~conducting-air hypothesis! the two-fluid problem reduces to the usual Be´nard- Marangoni ~BM! problem provided the spatial variations of the temperature in the thermal boundary conditions are considered. This approximation is the minimal model to compare with well-controlled BM experiments. The form of the average temperature profiles suggests the reference temperature that ought to be taken in nondimensional parameters that describe these phenomena. We also discuss how the Biot number could be estimated from the Nusselt number and the interfacial temperature field measurements even far from convective threshold. A linear stability analysis is performed with the correct thermal boundary condition. It gives thresholds that slightly differ from those obtained previously. These values are compared with recent experimental findings. All these facts will be useful in performing weakly nonlinear analyses and in planning future experiments on this instability.
- Mode-mode interaction for a CO2 laser with imperfect 0(2) symmetry(American Physical Society, 1993) López-Ruiz, R. (R.); Perez-Garcia, C. (C.); Mindlin, G.B. (G.B.)
- Phase instabilities in hexagonal patterns(European Physical Society, 1998) Perez-Garcia, C. (C.); Echebarría, B. (Blas)The general form of the amplitude equations for a hexagonal pattern including spatial terms is discussed. At the lowest order we obtain the phase equation for such patterns. The general expression of the di usion coe cients is given and the contributions of the new spatial terms are analysed in this paper. From these coe cients the phase stability regions in a hexagonal pattern are determined. In the case of B enard-Marangoni instability our results agree qualitatively with numerical simulations performed recently.
- Hydrothermal waves in Marangoni convection in a cylindrical container(American Physical Society, 1993) Burguete-Mas, F.J. (Francisco Javier); Perez-Garcia, C. (C.); Garcimartín-Montero, Á. (Ángel); Mancini-Maza, H. L. (Hector Luis); Ezersky, A. (A.)
- Stability of hexagonal patterns in Bénard-Marangoni convection(2001) Perez-Garcia, C. (C.); Echebarría, B. (Blas)Hexagonal patterns in Bénard-Marangoni BM convection are studied within the framework of amplitude equations. Near threshold they can be described with Ginzburg-Landau equations that include spatial quadratic terms. The planform selection problem between hexagons and rolls is investigated by explicitly calculating the coefficients of the Ginzburg-Landau equations in terms of the parameters of the fluid. The results are compared with previous studies and with recent experiments. In particular, steady hexagons that arise near onset can become unstable as a result of long-wave instabilities. Within weakly nonlinear theory, a two-dimensional phase equation for long-wave perturbations is derived. This equation allows us to find stability regions for hexagon patterns in BM convection.
- Influence of time dependent flows on the threshold of the kinematic dynamo action(2007) Burguete-Mas, F.J. (Francisco Javier); Perez-Garcia, C. (C.); Torre, A. (Alberto) de laA numerical study of the influence of slowly evolving velocity fields in the threshold of the dynamo action is presented. Using experimental time averaged velocity fields, harmonic variations are introduced in a kinematic code in order to characterize the response of the magnetic field to a broad range of frequencies. A critical frequency is found around ωc = 200 where a transition is obtained. For large values of the frequency (i.e. smaller periods) the magnetic field can not see the velocity fluctuations and the response of the system corresponds to that of the mean flow. For smaller frequencies, the magnetic field sees the slow evolution of the velocity field, and reduces significatively its growth rates when compared to the mean value. This loss of efficiency is due to the dissipation that appears during the transition between the magnetic eigenvectors corresponding to each one of the velocity fields.
- Fronts between hexagons and squares in a generalized Swift-Hohemberg equation(American Physical Society, 1996) Perez-Garcia, C. (C.); Herrero, H. (H.); Kubstrup, C. (C.)Pinning effects in domain walls separating different orientations in patterns in nonequilibrium systems are studied. Usually, theoretical studies consider perfect structures, but in experiments, point defects, grain boundaries, etc., always appear. The aim of this paper is to perform an analysis of the stability of fronts between hexagons and squares in a generalized Swift-Hohenberg model equation. We focus the analysis on pinned fronts between domains with different symmetries by using amplitude equations and by considering the small-scale structure in the pattern. The conditions for pinning effects and stable fronts are determined. This study is completed with direct simulations of the generalized Swift-Hohenberg equation. The results agree qualitatively with recent observations in convection and in ferrofluid instabilities.
- Dynamics of maps with a global multiplicative coupling(1991) López-Ruiz, R. (R.); Perez-Garcia, C. (C.)
- Realistic rotating convection in a binary viscoelastic mixture(2007) Laroze, D. (David); Perez-Garcia, C. (C.); Bragard, J. (Jean); Martinez-Mardones, J. (J.)In this work we report theoretical and numerical results on convection in a viscoelastic binary mixture under rotation for realistic rigid–rigid boundary conditions. We focus our analysis in the DNA aqueous suspensions. Instability thresholds for oscillatory convection are calculated. Finally, we analyze the stabilizing effect for the onset of convection.
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