We consider the linear stability of a horizontal fluid bilayer subject to vertical heating. The two layers consist of a binary fluid that has undergone a phase transition, resulting in a horizontal interphase boundary between two phases with different compositions. We perform linear stability calculations to determine critical values for the applied temperature difference across the system that is necessary to produce instability, using both numerical computations and small-wavenumber approximations. We focus on the instability due to the phase change, which can occur in the absence of buoyancy and surface-tension-driven convection. We find both direct and oscillatory modes of instability, both of which can persist to small wave numbers that allow approximate analytical descriptions. The interaction of flow with a deformable phase boundary plays a critical role in the instability, and the results are compared to morphological stability results that can be obtained in the absence of flow.
Citation: Physics of Fluids A-Fluid Dynamics
Pub Type: Journals
hydrodynamics, phase transformation, binary fluid, liquid bilayers, morphological stability