Permanent Excitation of Standing Gravity Surface Waves by the Resonant Coalescence of Non-Coalescent Cold and Hot Pure Liquid

We describe the continuous excitation of standing gravity surface waves in the free surface of a volatile silicone oil contained in a cylindrical heated vessel (crucible). Resonant coalescence occurred under certain conditions between the fluid in the vessel and a volume of condensed oil which forms at the lower end of a cold copper cylinder in contact from above with the center of the oil surface. The expected continuous coalescence between the cold and the hot fluid volumes does not occur if the cold cylinder is raised above a critical height from the fluid surface forming a free-standing liquid column (meniscus). The standing waves frequency is fixed by the geometry and repeated partial coalescence events are triggered by the standing wave. The thermal Marangoni effect during the partial coalescence events leads to resonant wave amplification.