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Large-scale convective flow sustained by thermally active Lagrangian tracers

Published online by Cambridge University Press:  02 December 2022

Lokahith Agasthya*
Affiliation:
Department of Physics, University of Rome ‘Tor Vergata’ and INFN, Via della Ricerca Scientifica 1, 00133 Rome RM, Italy Angewandte Mathematik und Numerische Analysis, Bergische Universität Wuppertal, Gaußstrasse 20, D-42119 Wuppertal, Germany Computation-based Science and Technology Research Center, The Cyprus Institute, 20 Kavafi Str., Nicosia 2121, Cyprus
Andreas Bartel
Affiliation:
Angewandte Mathematik und Numerische Analysis, Bergische Universität Wuppertal, Gaußstrasse 20, D-42119 Wuppertal, Germany
Luca Biferale
Affiliation:
Department of Physics, University of Rome ‘Tor Vergata’ and INFN, Via della Ricerca Scientifica 1, 00133 Rome RM, Italy
Matthias Ehrhardt
Affiliation:
Angewandte Mathematik und Numerische Analysis, Bergische Universität Wuppertal, Gaußstrasse 20, D-42119 Wuppertal, Germany
Federico Toschi
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
*
Email address for correspondence: lnagasthya@gmail.com

Abstract

Non-isothermal particles suspended in a fluid lead to complex interactions – the particles respond to changes in the fluid flow, which in turn is modified by their temperature anomaly. Here, we perform a novel proof-of-concept numerical study based on tracer particles that are thermally coupled to the fluid. We imagine that particles can adjust their internal temperature reacting to some local fluid properties, and follow simple, hard-wired active control protocols. We study the case where instabilities are induced by switching the particle temperature from hot to cold depending on whether it is ascending or descending in the flow. A macroscopic transition from stable to unstable convective flow is achieved, depending on the number of active particles and their excess negative/positive temperature. The stable state is characterized by a flow with low turbulent kinetic energy, strongly stable temperature gradient, and no large-scale features. The convective state is characterized by higher turbulent kinetic energy, self-sustaining large-scale convection, and weakly stable temperature gradients. Individually, the particles promote the formation of stable temperature gradients, while their aggregated effect induces large-scale convection. When the Lagrangian temperature scale is small, a weakly convective laminar system forms. The Lagrangian approach is also compared to a uniform Eulerian bulk heating with the same mean injection profile, and no such transition is observed. Our empirical approach shows that thermal convection can be controlled by pure Lagrangian forcing, and opens the way for other data-driven particle-based protocols to enhance or deplete large-scale motion in thermal flows.

Information

Type
JFM Papers
Copyright
© The Author(s), 2022. Published by Cambridge University Press

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