Vibroconvective Patterns in a Layer under Translational Vibrations of Circular Polarization

Abstract

This article experimentally investigates thermal vibrational convection in horizontal layers, subject to circular translational oscillations in the horizontal plane. The definite direction of translational vibrations lacks investigation, and the case of a layer heated from above is considered. At large negative values of the gravitational Rayleigh number, the thermovibrational convection appears in a threshold manner with an increase in the vibration intensity. Our results show that in the case of strong gravitational stabilization, thermovibrational convection develops in the form of patterns with strong anisotropy of spatial periods in orthogonal directions. The vibroconvective patterns have the form of parallel rolls divided along their length into relatively short segments. The layer thickness determines the distance between the rolls, and the longitudinal wavelength, depends on the Rayleigh number. Convective cells are studied using the noninvasive thermohromic methodic. It is found that when using the tracers for flow visualization, the concentration and type of the visualizer particles have a serious impact on the shape of the observed vibroconvective structures. In particular, the presence of even a small number of tracers (used in the study of velocity fields by the PIV method) generates flows and intensifies the heat transfer below the threshold of thermovibrational convection excitation.

Thermal Vibrational Convection in a Rotating Plane Layer

“…Begin the study of vibrational thermal convection generated by a rotating force field in a cavity that performs independent rotation with the limiting case of no rotation. The researches of the problem in this statement was started in (Kozlov et al 2021). The visualization technique with using thermochromic film described above makes it possible to display weak changes in liquid temperature near the lower "cold" boundary of the cavity.…”

“…Thermal vibrational convection under the action of circularly polarized translational vibrations was theoretically considered in (Kozlov 1991, Pesch et al 2008, in this case, the uniform inertial force field rotates in the reference frame of the cavity. An experimental study of thermovibrational convection in a plane horizontal liquid layer heated from above was carried out in (Kozlov et al 2019, Kozlov et al 2021. Under conditions of large negative values of the gravitational Rayleigh number, it was found that vibrational convection develops in the form of spatial structures, where the elongated convective rolls are broken along the length into relatively short segments forming a beads-like pattern.…”

Thermal Flows

“…Following the treatment of thermogravitational and thermocapillary convection, two studies [8,9] are also included, which concentrate on a third fundamental variant of thermally induced flows, namely fluid motion produced in non-isothermal systems by the application of "vibrations" (thermovibrational convection). Vibrations enable a timevarying acceleration, which formally makes the emerging convective structures a variant of buoyancy convection.…”

“…The need to overcome a threshold to induce convection from an initial quiescent state, together with the opposite tendency of acceleration to damp fluid motion when its sign is reversed, causes a variety of possible solutions that can display synchronous, non-synchronous, time-periodic and multi-frequency responses. A very special case is represented by "circular translational vibrations", i.e., a situation where the entire fluid domain moves along a circular path [9]. The peculiarity of this flow originates from the absence of a preferred direction for the vibrations and the existence of a rotating force field in the non-inertial reference frame moving with the fluid container.…”

“…The "rotating fluid" theme, already addressed to a certain extent in [9] and in [2][3][4], returns (although under different perspectives) in [10], where the main purpose is the presentation of an analytical dependence on the critical Reynolds number for a flow near a rotating disk (such a subject being essential for the analysis of the thermal response of disks and blades in relation to the design of gas and steam turbines).…”