Experimental investigation of turbulent Rayleigh-Bénard convection of water in a cylindrical cell: The Prandtl number effects for Pr > 1

2020 ◽  
Vol 32 (1) ◽  
pp. 015101 ◽  
Author(s):  
Ying-Hui Yang ◽  
Xu Zhu ◽  
Bo-Fu Wang ◽  
Yu-Lu Liu ◽  
Quan Zhou
Keyword(s):  
Experimental Investigation ◽  
Prandtl Number ◽  
Cylindrical Cell ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

scholarly journals Experimental investigation of longitudinal space–time correlations of the velocity field in turbulent Rayleigh–Bénard convection

2011 ◽  
Vol 683 ◽  
pp. 94-111 ◽  
Author(s):  
Quan Zhou ◽  
Chun-Mei Li ◽  
Zhi-Ming Lu ◽  
Yu-Lu Liu
Keyword(s):  
Experimental Investigation ◽  
Velocity Field ◽  
Space Time ◽  
Turbulent Shear ◽  
Convection Cell ◽  
Mean Velocity ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

AbstractWe report an experimental investigation of the longitudinal space–time cross-correlation function of the velocity field, $C(r, \tau )$, in a cylindrical turbulent Rayleigh–Bénard convection cell using the particle image velocimetry (PIV) technique. We show that while Taylor’s frozen-flow hypothesis does not hold in turbulent thermal convection, the recent elliptic model advanced for turbulent shear flows (He & Zhang, Phys. Rev. E, vol. 73, 055303) is valid for the present velocity field for all over the cell, i.e. the isocorrelation contours of the measured $C(r, \tau )$ have an elliptical curve shape and hence $C(r, \tau )$ can be related to $C({r}_{E} , 0)$ via ${ r}_{E}^{2} = (r\ensuremath{-} U\tau )^{2} + {V}^{2} {\tau }^{2} $ with $U$ and $V$ being two characteristic velocities. We further show that the fitted $U$ is proportional to the mean velocity of the flow, but the values of $V$ are larger than the theoretical predictions. Specifically, we focus on two representative regions in the cell: the region near the cell sidewall and the cell’s central region. It is found that $U$ and $V$ are approximately the same near the sidewall, while $U\simeq 0$ at the cell centre.

scholarly journals Kinetic energy transport in Rayleigh–Bénard convection

2015 ◽  
Vol 773 ◽  
pp. 395-417 ◽  
Author(s):  
K. Petschel ◽  
S. Stellmach ◽  
M. Wilczek ◽  
J. Lülff ◽  
U. Hansen
Keyword(s):  
Energy Balance ◽  
Kinetic Energy ◽  
Prandtl Number ◽  
Viscous Dissipation ◽  
Energy Transport ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
Viscous Stresses

The kinetic energy balance in Rayleigh–Bénard convection is investigated by means of direct numerical simulations for the Prandtl number range $0.01\leqslant \mathit{Pr}\leqslant 150$ and for fixed Rayleigh number $\mathit{Ra}=5\times 10^{6}$. The kinetic energy balance is divided into a dissipation, a production and a flux term. We discuss the profiles of all the terms and find that the different contributions to the energy balance can be spatially separated into regions where kinetic energy is produced and where kinetic energy is dissipated. By analysing the Prandtl number dependence of the kinetic energy balance, we show that the height dependence of the mean viscous dissipation is closely related to the flux of kinetic energy. We show that the flux of kinetic energy can be divided into four additive contributions, each representing a different elementary physical process (advection, buoyancy, normal viscous stresses and viscous shear stresses). The behaviour of these individual flux contributions is found to be surprisingly rich and exhibits a pronounced Prandtl number dependence. Different flux contributions dominate the kinetic energy transport at different depths, such that a comprehensive discussion requires a decomposition of the domain into a considerable number of sublayers. On a less detailed level, our results reveal that advective kinetic energy fluxes play a key role in balancing the near-wall dissipation at low Prandtl number, whereas normal viscous stresses are particularly important at high Prandtl number. Finally, our work reveals that classical velocity boundary layers are deeply connected to the kinetic energy transport, but fail to correctly represent regions of enhanced viscous dissipation.

Sign in / Sign up

Export Citation Format

Share Document