We analyze the transport and deposition behavior of dilute microparticles in turbulent Rayleigh–Bénard convection. Two-dimensional direct numerical simulations were carried out for the Rayleigh number (Ra) of 108 and the Prandtl number (Pr) of 0.71 (corresponding to the working fluids of air). The Lagrangian point particle model was used to describe the motion of microparticles in the turbulence. Our results show that the suspended particles are homogeneously distributed in the turbulence for the Stokes number (St) less than 10−3, and they tend to cluster into bands for 10−3 ≲ St ≲ 10−2. At even larger St, the microparticles will quickly sediment in the convection. We also calculate the mean-square displacement (MSD) of the particle’s trajectories. At short time intervals, the MSD exhibits a ballistic regime, and it is isotropic in vertical and lateral directions; at longer time intervals, the MSD reflects a confined motion for the particles, and it is anisotropic in different directions. We further obtained a phase diagram of the particle deposition positions on the wall, and we identified three deposition states depending on the particle’s density and diameter. An interesting finding is that the dispersed particles preferred to deposit on the vertical wall where the hot plumes arise, which is verified by tilting the cell and altering the rotation direction of the large-scale circulation.
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August 2020
Research Article|
August 03 2020
Transport and deposition of dilute microparticles in turbulent thermal convection
Special Collection:
Recent Advances in Theory, Simulations, and Experiments on Multiphase Flows
Ao Xu (徐翱)
;
Ao Xu (徐翱)
a)
1
School of Aeronautics, Northwestern Polytechnical University
, Xi’an 710072, China
a)Author to whom correspondence should be addressed: axu@nwpu.edu.cn
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Shi Tao (陶实)
;
Shi Tao (陶实)
2
Key Laboratory of Distributed Energy Systems of Guangdong Province, Dongguan University of Technology
, Dongguan 523808, China
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Le Shi (史乐)
;
Le Shi (史乐)
3
State Key Laboratory of Electrical Insulation and Power Equipment, Center of Nanomaterials for Renewable Energy, School of Electrical Engineering, Xi’an Jiaotong University
, Xi’an 710049, China
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Heng-Dong Xi (郗恒东)
Heng-Dong Xi (郗恒东)
1
School of Aeronautics, Northwestern Polytechnical University
, Xi’an 710072, China
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a)Author to whom correspondence should be addressed: axu@nwpu.edu.cn
Note: This paper is part of the Special Topic, Recent Advances in Theory, Simulations, and Experiments on Multiphase Flows.
Physics of Fluids 32, 083301 (2020)
Article history
Received:
June 17 2020
Accepted:
July 16 2020
Citation
Ao Xu, Shi Tao, Le Shi, Heng-Dong Xi; Transport and deposition of dilute microparticles in turbulent thermal convection. Physics of Fluids 1 August 2020; 32 (8): 083301. https://doi.org/10.1063/5.0018804
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