Thermographic analysis of topographically controlled Marangoni–Rayleigh–Bénard convection in a fluid with temperature-dependent properties

Waris, Wasim and Lappa, Marcello (2024) Thermographic analysis of topographically controlled Marangoni–Rayleigh–Bénard convection in a fluid with temperature-dependent properties. International Journal of Thermal Sciences, 196. 108718. ISSN 1290-0729 (https://doi.org/10.1016/j.ijthermalsci.2023.108718)

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Abstract

Thermal convection in a shallow layer of liquid with an array of metallic (Aluminum) cubic elements evenly spaced along the bottom is investigated experimentally using a thermographic technique. The blocks protrude upwards and, although they are prevented from reaching the free surface, their vertical thickness, horizontal size and overall number can be varied parametrically. This configuration is used with the two-fold intention to produce a kind of obstruction or blockage in the flow and, at the same time, to feed thermal convection with heat directly injected into the fluid at a certain distance from the (hot) floor. It is shown that tuning of the physical topography at the bottom and the difference of temperature between the liquid and the external (gaseous) environment is instrumental in enabling internal feedback control over the spontaneous flow behavior. For a fixed geometry and temperature difference, variations in the emerging pattern can also be produced by changing the thickness of the liquid layer, which indirectly provides evidence for the additional degree of freedom represented by the relative importance of buoyancy and Marangoni effects. Overall, such results suggest a novel possible route to the realization of convective motions with complex (but surprisingly regular) organization, which have been rarely obtained in earlier attempts based on conventional setups.

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