Spatial forcing in pattern forming thermal convection
A thin horizontal fluid layer, heated from below and cooled from above is an archetype for a pattern forming system and has thus extensively been studied in the past to investigate how patterns emerge in an isotropic and homogeneous system. There, for small control parameters (i.e. the dimensionless temperature difference between both plates), fluid motion occurs in the form of long rolls with an arbitrary orientation and a well defined periodicity. Most natural pattern forming systems, however, are anisotropic and subject to a variety of inhomogeneities. In our experiment, we use a warm plate that has a one-dimensional surface texture imprinted. In this way an external mode is applied to the system that interact with the natural modes of the unforced system. In addition, we break the rotational symmetry by inclining the fluid layer. The interaction between natural modes and the external forcing leads to a variety of new exotic patterns. We observe and investigate the occurring patterns as a function of the temperature difference, the inclination angle and the direction of inclination. We will see that this rather simple forcing scheme can stabilize spatiotemporally chaotic patterns but it can also destabilize steady patterns, depending on the forcing parameters.