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DOI: 10.1615/HeatTransRes.2018021333
pages 1825-1836

FLUCTUATING LOCAL DISSIPATION SCALES OF TURBULENT RAYLEIGH–BÉNARD CONVECTION USING THE LATTICE BOLTZMANN METHOD

Yikun Wei
State-Province Joint Engineering Lab of Fluid Transmission System Technology Faulty of Mechanical Engineering and Automation, Zhejiang Sci-Tech University, China
Yuxin Lun
Faculty of Mechanical Engineering and Automatic, Zhejiang Scientific Technical University, Key Laboratory of Fluid Transmission Technology of Zhejiang, State-Province Joint Engineering Laboratory of Fluid Transmission System Technology, 310018, Hangzhou, China
Lei Zhang
Faculty of Mechanical Engineering and Automatic, Zhejiang Scientific Technical University, Key Laboratory of Fluid Transmission Technology of Zhejiang, State-Province Joint Engineering Laboratory of Fluid Transmission System Technology, 310018, Hangzhou, China
Yuehong Qian
School of Mathematical Science, Soochow University, 215006, Jiangsu, China

ABSTRACT

Fluctuating local dissipation scales for turbulent Rayleigh–Bénard (RB) convection are investigated using the lattice Boltzmann method (LBM) at different Rayleigh numbers (Ra). Special attention is paid to the fluctuating local dissipation scales for turbulent RB convection, the probability density function (PDF) of the local dissipation scale and PDF of the dissipation rates at different Ra. It is observed that a further increase of Ra tears off unstable spokes to form more independent large-scale flow structures generated in the thermal boundary layers and driven by buoyancy. It is validated that the fluctuations of the energy dissipation field can directly be translated into a fluctuating local dissipation scale, which is found to develop ever finer fluctuations with increasing Ra. It is noted that the scales in the whole cell cover a wider range, both to the large-scale and small-scale end which is centered around the most probable value.