Faraday instability in double-interface fluid layers

We investigate, both by way of theory and by experiments, the mechanically forced Faraday instability in immiscible three-fluid systems that is two-interface fluid layers. The theoretical model suggests that two-interface fluid layers offer underlying physics quite distinct from the typical single-interface system due to the coupling of the fluid interfaces, resulting in alternating double-tongued stability curves. This allows for the possibility of unique codimension points unattainable in traditional two-fluid systems. In addition, the presence of a third fluid in the problem can lead to either enhanced or delayed destabilization of the system at target frequencies. Experimental results qualitatively support the theory, though precise agreement between the theory and the experiment is hindered due to the sidewall damping.