Molecular hints of two-step transition to convective flow via streamline percolation Garrido Galera, Pedro Luis Hurtado Fernández, Pablo Ignacio Financial support from Spanish Ministry MINECO Project No. FIS2017-84256-P and Junta de Andalucía Grant No. A-FQM-175-UGR18, both supported by the European Regional Development Fund, is acknowledged. This work is also part of the Project of I+D+i Ref. No. PID2020-113681GBI00, financed by MICIN/AEI/10.13039/501100011033 and FEDER A Way to Make Europe. We are also grateful for the computational resources and assistance provided by PROTEUS, the supercomputing center of Institute Carlos I for Theoretical and Computational Physics at the University of Granada, Spain. Convection is a key transport phenomenon important in many different areas, from hydrodynamics and ocean circulation to planetary atmospheres or stellar physics. However, its microscopic understanding still remains challenging. Here we numerically investigate the onset of convective flow in a compressible (non-Oberbeck- Boussinesq) hard disk fluid under a temperature gradient in a gravitational field.We uncover a surprising two-step transition scenario with two different critical temperatures. When the bottom plate temperature reaches a first threshold, convection kicks in (as shown by a structured velocity field) but gravity results in hindered heat transport as compared to the gravity-free case. It is at a second (higher) temperature that a percolation transition of advection zones connecting the hot and cold plates triggers efficient convective heat transport. Interestingly, this picture for the convection instability opens the door to unknown piecewise-continuous solutions to the Navier-Stokes equations. 2022-09-28T09:36:52Z 2022-09-28T09:36:52Z 2022-07-28 info:eu-repo/semantics/article L. Garrido and P. I. Hurtado. Molecular hints of two-step transition to convective flow via streamline percolation. Phys. Rev. E 106, 014144 [https://doi.org/10.1103/PhysRevE.106.014144] https://hdl.handle.net/10481/77043 10.1103/PhysRevE.106.014144 eng http://creativecommons.org/licenses/by-nc-nd/4.0/ info:eu-repo/semantics/openAccess Attribution-NonCommercial-NoDerivatives 4.0 Internacional American Physical Society