Abstract:
Thermal turbulence is ubiquitous in nature and industry, which is a kind of convection driven by density difference due to the temperature gradient. Turbulent Rayleigh-Bénard (RB) convection is a basic research paradigm subtracting from the actual complicate problems. In the past decades, RB convection had been widely used to study the turbulent heat transport, flow structure evolution and other fundamental mechanisms. Recently, it is found that under the same control parameters, the RB convection exhibits different turbulent flow states (structures) and there is a one-to-one correspondence between the turbulent flow states and heat transport efficiencies. Thus, uncovering the mechanism of the emergence of different turbulent flow states (structures) is beneficial to control the heat transport efficiency of RB convection. In this paper, we focus on the multiple flow states phenomena in turbulent RB convection and review recent progresses. We also point out the issues and challenges and give an outlook on the future research.