Xiaozhou He

Harbin Institute of Technology Shenzhen Graduate School | HITSZ · Azimuthal diffusion of the large-scale-circulation plane, and absence of significant non-Boussinesq effects, in turbulent convection near the ultimate-state transition

While the heat transfer and the flow dynamics in a cylindrical Rayleigh-Bénard (RB) cell are rather independent of the aspect ratio Γ (diameter/height) for large Γ, a small-Γ cell considerably stabilizes the flow and thus affects the heat transfer. Here, we first theoretically and numerically show that the critical Rayleigh number for the onset of...

DOI:https://doi.org/10.1103/PhysRevLett.124.229402

We present measurements of the orientation $\theta_0$ and temperature amplitude $\delta$ of the large-scale circulation in a cylindrical sample of turbulent Rayleigh-Benard convection (RBC) with aspect ratio $\Gamma \equiv D/L = 1.00$ ($D$ and $L$ are the diameter and height respectively) and for the Prandtl number $Pr \simeq 0.8$. Results for $\th...

We report results of Reynolds-number measurements, based on multi-point temperature measurements and the elliptic approximation (EA) of He and Zhang (2006 Phys. Rev. E 73 055303), Zhao and He (2009 Phys. Rev. E 79 046316) for turbulent Rayleigh–Bénard convection (RBC) over the Rayleigh-number range 1011 ≲ Ra ≲ 2 × 1014 and for a Prandtl number Pr ≃...

We report on experimental determinations of the temperature field in the interior (bulk) of turbulent Rayleigh-Benard convection for a cylindrical sample with aspect ratio (diameter over height) of 0.50, both in the classical and in the ultimate state. The Prandtl number was close to 0.8. We find a "logarithmic layer" in which the temperature varie...

The scaling properties of the temperature structure function (SF) and temperature– velocity cross-structure function (CSF) are investigated in turbulent Rayleigh–Bénard convection (RBC). The measured SFs and CSFs exhibit good scaling in space and time and the resulting SF and CSF exponents are obtained both at the centre of the convection cell and...

The recent development of the elliptic model (He, et al. Phy. Rev. E, 2006), which predicts that the space-time correlation function C u (r, τ) in a turbulent flow has a scaling form C u (r E , 0) with r E being a combined space-time separation involving spatial separation r and time delay τ, has stimulated considerable experimental efforts aimed a...

We report measurements of the temperature variance $\sigma^2(z,r)$ and frequency power spectrum $P(f,z,r)$ ($z$ is the distance from the sample bottom and $r$ the radial coordinate) in turbulent Rayleigh-B\'enard convection (RBC) for Rayleigh numbers $\textrm{Ra} = 1.6\times10^{13}$ and $1.1\times10^{15}$ and for a Prandtl number $\textrm{Pr} \sime...

A Comment on the Letter by P. Urban, P. Hanzelka, T. Kralik, V. Musilova, A. Srnka, and L. Skrbek, Phys. Rev. Lett. 109, 154301 (2012). The authors of the Letter offer a Reply.

We show that the nature of the scaling behavior can be revealed by studying the conditional structure functions evaluated at given values of the locally averaged thermal dissipation rate. These conditional structure functions have power-law dependence on the value of the locally averaged thermal dissipation rate, and such dependence for the Bolgian...

We report on the experimental results for heat-transport measurements, in the form of the Nusselt number Nu, by turbulent Rayleigh–Bénard convection (RBC) in a cylindrical sample of aspect ratio Γ ≡ D/L = 0.50 (D = 1.12 m is the diameter and L = 2.24 m the height). The measurements were made using sulfur hexafluoride at pressures up to 19 bar as th...

We report experimental results for heat-transport measurements, in the form of the Nusselt number Nu, by turbulent Rayleigh–Bénard convection (RBC) in a cylindrical sample of aspect ratio Γ ≡ D/L = 1.00 (D = 1.12 m is the diameter and L = 1.12 m the height) and compare them with previously reported results for Γ = 0.50. The measurements were made u...

We report results for the temperature profiles of turbulent Rayleigh-Bénard convection (RBC) in the interior of a cylindrical sample of aspect ratio Γ ≡ D/L = 0.50 (D and L are the diameter and height respectively). Results from experiment over the Rayleigh number range 4×10 12 < ∼ Ra < ∼ 10 15 for a Prandtl number Pr ≃ 0.8 and from direct numerica...

Measurements of the Nusselt number Nu and of a Reynolds number Re(eff) for Rayleigh-Bénard convection (RBC) over the Rayleigh-number range 10(12)≲Ra≲10(15) and for Prandtl numbers Pr near 0.8 are presented. The aspect ratio Γ≡D/L of a cylindrical sample was 0.50. For Ra≲10(13) the data yielded Nu∝Ra(γ(eff)) with γ(eff)≃0.31 and Re(eff)∝Ra(ζ(eff)) w...

We report an experimental study of the temperature space-time cross-correlation function, C{T}(r,τ), in the central region of turbulent Rayleigh-Bénard convection. The measured C{T}(r,τ) is found to have the scaling form C{T}(r{E},0), where r{E}=[r² +(Vτ)²]¹/² with V being the rms velocity at the center of the convection cell. The experiment confir...

Using a homemade local temperature gradient probe, the instantaneous thermal dissipation rate T r , t is obtained in an aspect-ratio-one cylindrical convection cell filled with water. From the time series measurements, a locally averaged thermal dissipation r , t over a time interval is constructed. Herein we decompose r , t into three contribution...

The space-time cross-correlation function C(T)(r,τ) of local temperature fluctuations in turbulent Rayleigh-Bénard convection is obtained from simultaneous two-point time series measurements. The obtained C(T)(r,τ) is found to have the scaling form C(T)(r(E),0) with r(E)=[(r-Uτ)(2)+V(2)τ(2)](1/2), where U and V are two characteristic velocities ass...

From the measured thermal dissipation rate in turbulent Rayleigh–Bénard convection in a cylindrical cell, we construct a locally averaged thermal dissipation rate χ f τ by averaging over a time interval τ . We study how the statistical moments (χ f τ) p depend on τ at various locations along the vertical axis of the convection cell. We find that (χ...

A systematic study of the thermal dissipation field and its statistical properties is carried out in turbulent Rayleigh-Bénard convection. A local temperature gradient probe consisting of four identical thermistors is made to measure the normalized thermal dissipation rate epsilonN(r) in two convection cells filled with water. The measurements are...

The time-averaged local thermal dissipation rate epsilonN(r) in turbulent convection is obtained from direct measurements of the temperature gradient vector in a cylindrical cell filled with water. It is found that epsilonN(r) contains two contributions. One is generated by thermal plumes, present mainly in the plume-dominated bulk region, and decr...