Quan Zhou

Quan Zhou
Shanghai University | SHU

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21
Publications
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Publications

Publications (21)
Article
Full-text available
We report high-spatial-resolution measurements of the thermal boundary layer (BL) properties in turbulent thermal convection. The experiment was made near the lower conducting plate of a water-filled rectangular convection cell of height 0.76 m, with a Prandtl number Pr = 4.3 and over the Rayleigh-number range 2 × 10 10 < Ra < 7 × 10 11 . Time seri...
Article
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We numerically investigate the structures of the near-plate temperature profiles close to the bottom and top plates of turbulent Rayleigh-Bénard flow in a cylindrical sample at Rayleigh numbers Ra = 10(8) to Ra = 2 × 10(12) and Prandtl numbers Pr = 6.4 and Pr = 0.7 with the dynamical frame method [Zhou and Xia, Phys. Rev. Lett. 104, 104301 (2010)],...
Article
Full-text available
We present direct multi-point velocity measurements of the two-dimensional velocity fields in a cylindrical Rayleigh-Benard convection cell using the particle image velocimetry (PIV) technique over the Rayleigh number range 5.9 × 109 Ra 1.1 × 1011. The longitudinal integral length scale of the horizontal and vertical velocity fields are obtained at...
Article
Full-text available
We investigate the structures of the near-plate velocity and temperature profiles at different horizontal positions along the conducting bottom (and top) plate of a Rayleigh-Bénard convection cell, using two-dimensional (2D) numerical data obtained at the Rayleigh number Ra = 108 and the Prandtl number Pr = 4.4 of an Oberbeck-Boussinesq flow with c...
Article
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We present a method of disentangling the anisotropies produced by the cliff structures in turbulent velocity field and test it in the system of turbulent Rayleigh-B\'{e}nard (RB) convection. It is found that in the RB system the cliff structures in the velocity field are generated by thermal plumes. These cliff structures induce asymmetry in the ve...
Article
Full-text available
The shapes of the velocity and temperature profiles near the horizontal conducting plates' centre regions in turbulent Rayleigh–Bénard convection are studied numerically and experimentally over the Rayleigh number range 108 ≲ Ra ≲ 3 × 1011 and the Prandtl number range 0.7 ≲ Pr ≲ 5.4. The results show that both the temperature and velocity profiles...
Article
Full-text available
We report on measurements of a two-dimensional (2D) dye concentration field in turbulent Rayleigh–Bénard (RB) convection using the planar laser-induced fluorescence technique. The measurements were made in a vertical plane near the sidewall of a rectangular convection cell filled with water and with the Rayleigh number Ra varying from 109 to 1010,...
Article
Full-text available
We present a systematic experimental study of geometric and physical properties of thermal plumes in turbulent Rayleigh–Bénard convection using the thermochromic-liquid-crystal (TLC) technique. The experiments were performed in three water-filled cylindrical convection cells with aspect ratios 2, 1 and 0.5 and over the Rayleigh number range 5×107≤R...
Article
Full-text available
We report measurements of the instantaneous viscous boundary layer (BL) thickness delta(v)(t) in turbulent Rayleigh-Bénard convection. It is found that delta(v)(t) obtained from the measured instantaneous two-dimensional velocity field exhibits intermittent fluctuations. For small values, delta(v)(t) obeys a lognormal distribution, whereas for larg...
Article
Full-text available
We report an experimental investigation of the local dissipation scale field eta in turbulent thermal convection. Our results reveal two types of universality of eta. The first one is that, for the same flow, the probability density functions (PDFs) of eta are insensitive to turbulent intensity and large-scale inhomogeneity and anisotropy of the sy...
Article
Full-text available
We present a systematic experimental study of geometric and statistical properties of thermal plumes in turbulent Rayleigh-B\'{e}nard convection using the thermochromic-liquid-crystal (TLC) technique. The experiments were performed in three water-filled cylindrical convection cells with aspect ratios 2, 1, and 0.5 and over the Rayleigh-number range...
Article
We report measurements of the instantaneous viscous boundary layer (BL) thickness deltav(t) in turbulent Rayleigh-Benard convection. The instantaneous deltav(t) obtained from PIV-measured two-dimensional velocity field is found to exhibit intermittent fluctuations. It is also found that there is a clean separation of statistical behavior of deltav(...
Article
Full-text available
We report measurements of the instantaneous viscous boundary layer (BL) thickness $\delta_v(t)$ in turbulent Rayleigh-B\'{e}nard convection. It is found that $\delta_v(t)$ obtained from the measured instantaneous two-dimensional velocity field exhibits intermittent fluctuations. For small values, $\delta_v(t)$ obeys a lognormal distribution, wherea...
Article
Full-text available
We report an experimental study of the large-scale circulation (LSC) in a turbulent Rayleigh–Bénard convection cell with aspect ratio unity. The temperature-extrema-extraction (TEE) method for obtaining the dynamic information of the LSC is presented. With this method, the azimuthal angular positions of the hot ascending and cold descending flows a...
Article
Full-text available
We report an experimental study of the three-dimensional spatial structure of the low-frequency temperature oscillations in a cylindrical Rayleigh-Bénard convection cell. Through simultaneous multipoint temperature measurements it is found that, contrary to the popular scenario, thermal plumes are emitted neither periodically nor alternately, but r...
Article
Full-text available
We report an experimental study of the large-scale circulation (LSC) in a turbulent Rayleigh-B\'{e}nard convection cell with aspect ratio unity. The temperature-extremum-extraction (TEE) method for obtaining the dynamic information of the LSC is presented. With this method, the azimuthal angular positions of the hot ascending and cold descending fl...
Article
Full-text available
We investigate experimentally the statistical properties of active and passive scalar fields in turbulent Rayleigh-Bénard convection in water, at Ra approximately 10;{10} . Both the local concentration of fluorescence dye and the local temperature are measured near the sidewall of a rectangular cell. It is found that, although they are advected by...
Article
Full-text available
We present direct multipoint velocity measurements of the two-dimensional velocity field in the central region of turbulent Rayleigh–Bénard convection. The local homogeneity and isotropy of the velocity field are tested using a number of criteria and are found to hold to an excellent degree. The properties of velocity circulation Γr are also studie...
Article
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An experimental study of the morphological evolution of thermal plumes in turbulent thermal convection is presented. Individual sheetlike plumes are extracted and their area, circumference, and "heat content" are found to all exhibit log-normal distributions. As the sheetlike plumes move across the plate they collide and convolute into spiraling sw...
Article
Full-text available
Direct multipoint measurements of the velocity and temperature fields have been made in a turbulent Rayleigh-Bénard convection cell. In the central region of the cell it is found that both velocity and temperature exhibit the same scaling behavior that one would find for the velocity and for a passive scalar in homogeneous and isotropic Navier-Stok...
Article
Full-text available
We present an experimental study of the azimuthal motion of the mean wind in turbulent thermal convection. The experiments were conducted with cylindrical convection cells of unity aspect ratio and over the range of the Rayleigh number from 1 x 10(9) to 1 x 10(10). The azimuthal angle of the circulation plane of the mean wind was measured using bot...

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Project
research Rayleigh-Bénard convection