Regular dendritic patterns induced by nonlocal time-periodic forcing

The dynamic response of dendritic solidification to spatially homogeneous t ime-periodic forcing has been studied. Phase-field calculations performed i n two dimensions (2D) and experiments on thin (quasi-2D) liquid-crystal lay ers show that the frequency of dendritic side branching can be tuned by osc illatory pressure or heating. The sensitivity of this phenomenon to the rel evant parameters, the frequency and amplitude of the modulation, the initia l undercooling and the anisotropies of the interfacial free energy, and mol ecule attachment kinetics, has been explored. It has been demonstrated that in addition the side-branching mode synchronous with external forcing as e merging from the linear Wentzel-Kramers-Brillouin analysis, modes that osci llate with higher harmonic frequencies are also present with perceptible am plitudes.