Thermally-driven flows and turbulence in vibrated liquids
Georgie Crewdson, Marcello Lappa
Abstract
Within the vast array of variants encompassed by thermal (buoyancy) convection, the particular interest of the present work is on the specific dynamics which are enabled when standard steady gravity is replaced by a time-periodic body force induced by vibrations. The study is designed as a set of separate problems, where each exemplar aims to unravel the implications of the fundamental properties of this type of flow. These include the symmetry of the emerging pattern as perceived by a real observer and as seen in a “time-averaged space”, the synchronous or non-synchronous response of the velocity field to the applied forcing, the magnitude of the so-called Thermofluid-dynamic (TFD) distortions and the peculiar route of evolution towards chaos. A kaleidoscope of previously unknown solutions is reported giving emphasis to some still poorly known aspects such as the complex nature of the textural transitions that take place in the flow as the Gershuni number is increased (from 3.30 × 102 to 5.00 × 107 for Pr = 15). It is shown that the low-frequency regime is relatively stable over this range. In addition to the standard quadrupolar pattern, in such a case peculiar convective structures emerge where the time-averaged rolls display a very regular columnar arrangement, which has been rarely observed in earlier studies. Chaotic states are enabled when larger frequencies of vibration are considered. While for intermediate frequencies concurrent aspects of the Feigenbaum and Manneville and Pomeau mechanisms can be recognized, the hallmark of the high frequency regime is its adherence to the standard Ruelle-Takens scenario.