Elliptical Instability and MultipleRoll Flow Modes of the LargeScale Circulation in Confined Turbulent RayleighBénard Convection
Abstract
The largescale circulation (LSC) of fluid is one of the main concepts in turbulent thermal convection as it is known to be important in global heat and mass transport in the system. In turbulent RayleighBénard convection (RBC) in slender containers, the LSC is formed of several dynamically changing convective rolls that are stacked on top of each other. The present study reveals the following two important facts: (i) the mechanism which causes the twisting and breaking of a singleroll LSC into multiple rolls is the elliptical instability and (ii) the heat and momentum transport in RBC, represented by the Nusselt (Nu) and Reynolds (Re) numbers, is always stronger (weaker) for smaller (larger) number n of the rolls in the LSC structure. Direct numerical simulations support the findings for n =1 ,…,4 and the diametertoheight aspect ratio of the cylindrical container Γ =1 /5 , the Prandtl number Pr =0.1 and Rayleigh number Ra =5 ×10^{5} . Thus, Nu and Re are, respectively, 2.5 and 1.5 times larger for a singleroll LSC (n =1 ) than for a LSC with n =4 rolls.
 Publication:

Physical Review Letters
 Pub Date:
 July 2020
 DOI:
 10.1103/PhysRevLett.125.054502
 arXiv:
 arXiv:2002.06951
 Bibcode:
 2020PhRvL.125e4502Z
 Keywords:

 Physics  Fluid Dynamics
 EPrint:
 Phys. Rev. Lett. 125, 054502 (2020)