Vibration-induced ‘anti-gravity’ tames thermal turbulence at high Rayleigh numbers

Abstract

We report that vertical vibration with small amplitude and high frequency can tame convective heat transport in Rayleigh–Bénard convection in a turbulent regime. When vertical vibration is applied, a dynamically averaged ‘anti-gravity’ results that stabilizes the thermal boundary layer and inhibits the eruption of thermal plumes. This eventually leads to the attenuation of the intensity of large-scale mean flow and a significant suppression of turbulent heat transport. Accounting for both the thermally led buoyancy and the vibration-induced anti-gravitational effects, we propose an effective Rayleigh number that helps to extend the Grossmann–Lohse theory to thermal vibrational turbulence. The prediction of the reduction on both the Nusselt and Reynolds numbers obtained by the extended model is found to agree well with the numerical data. In addition, vibrational influences on the mean flow structure and the temporal evolution of Nusselt and Reynolds numbers are investigated. The non-uniform characteristic of vibration-induced ‘anti-gravity’ is discussed. The present findings provide a powerful basis for studying thermal vibrational turbulence and put forward a novel strategy for actively controlling thermal turbulence.

Flow structure transition in thermal vibrational convection

“…2020; Wu et al. 2022 a ). A second-order finite-difference method is used for the spatial discretisation in a staggered grid.…”

“…Numerical simulations are performed using the in-house finite-difference code, which has been well validated in our previous studies (Wang et al 2020;Wu et al 2022a). A second-order finite-difference method is used for the spatial discretisation in a staggered grid.…”

“…This enhancement is achieved by vibration-induced boundary layer (BL) destabilisation, which breaks up the limitation of laminar BL for heat transport. In contrast, when vertical vibration is applied to the turbulent RB convection, the convective heat transport is suppressed (Wu et al 2022a) by inducing the anti-gravity effect that stabilises thermal BL and enhances thermal limitation. In addition to studying global quantities, Wu et al (2021) distinguish vibration-generated oscillatory flows and fluctuating fields in oscillatory RB convection with periodic lateral boundary conditions by using the phase decomposition method.…”

“…In contrast, when vertical vibration is applied to the turbulent RB convection, the convective heat transport is suppressed (Wu et al. 2022 a ) by inducing the anti-gravity effect that stabilises thermal BL and enhances thermal limitation. In addition to studying global quantities, Wu et al.…”

Unifying constitutive law of vibroconvective turbulence in microgravity

“…Vibration, omnipresent in science and technology, has been shown to be an attractive way to operate fluids, modulate convective patterns and control heat transport by creating an 'artificial gravity' (Beysens et al 2005;Beysens 2006), e.g. vibration shapes liquid interfaces in an arbitrary direction (Gaponenko et al 2015;Sánchez et al 2019Sánchez et al , 2020Apffel et al 2021), vibration levitates a fluid layer upon a gas layer (Apffel et al 2020), vibration selects patterns through the parametric response (Rogers et al 2000a,b;Pesch et al 2008;Salgado Sánchez et al 2019), vibration significantly enhances or suppresses heat transport depending on the mutual direction of vibration and temperature gradient (Swaminathan et al 2018;Wang et al 2020;Wu et al 2021Wu et al , 2022aGuo et al 2022;Wu, Wang & Zhou 2022b). Vibroconvection, resulting directly from a non-isothermal fluid subjected to the external vibration, is very pronounced under microgravity conditions and provides a potential mechanism of heat and mass transport in the absence of gravity-induced convection (Gershuni & Lyubimov 1998;Mialdun et al 2008;Shevtsova et al 2010).…”