Analysis of coherent structures in Rayleigh–Bénard convection

Abstract

Using direct numerical simulation, we investigate characteristics of coherent structures in Rayleigh–Bénard convection in a soft turbulence regime. The role of thermal plumes, essential structures in Rayleigh–Bénard convection, is studied by splitting flow regimes into thermal plume and background by investigating joint probability density function (PDF) of invariants of velocity gradient tensor. The contribution to thermal dissipation rate by these two regions is analysed separately. Through the joint PDF of invariants, we also examine the thermal effect on velocity structures.

Keywords:

• Rayleigh–Bénard convection
• turbulence
• direct numerical simulation
• coherent structure
• thermal plume
• velocity gradient tensor

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) [grant number 20090083510], [grant number 2014R1A2A2A01006544].