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Flow organization and heat transfer in turbulent wall sheared thermal convection
- Source :
- Journal of fluid mechanics, 897:A22. Cambridge University Press, Journal of Fluid Mechanics
- Publication Year :
- 2020
-
Abstract
- We perform direct numerical simulations of wall sheared Rayleigh-B\'enard (RB) convection for Rayleigh numbers up to $Ra=10^8$, Prandtl number unity, and wall shear Reynolds numbers up to $Re_w=10000$. Using the Monin-Obukhov length $L_{MO}$ we identify three different flow states, a buoyancy dominated regime ($L_{MO} \lesssim \lambda_{\theta}$; with $\lambda_{\theta}$ the thermal boundary layer thickness), a transitional regime ($0.5H \gtrsim L_{MO} \gtrsim \lambda_{\theta}$; with $H$ the height of the domain), and a shear dominated regime ($L_{MO} \gtrsim 0.5H$). In the buoyancy dominated regime the flow dynamics are similar to that of turbulent thermal convection. The transitional regime is characterized by rolls that are increasingly elongated with increasing shear. The flow in the shear dominated regime consists of very large-scale meandering rolls, similar to the ones found in conventional Couette flow. As a consequence of these different flow regimes, for fixed $Ra$ and with increasing shear, the heat transfer first decreases, due to the breakup of the thermal rolls, and then increases at the beginning of the shear dominated regime. For $L_{MO} \gtrsim 0.5H$ the Nusselt number $Nu$ effectively scales as $Nu \sim Ra^{\alpha}$, with $\alpha \ll 1/3$ while we find $\alpha \simeq 0.31$ in the buoyancy dominated regime. In the transitional regime the effective scaling exponent is $\alpha > 1/3$, but the temperature and velocity profiles in this regime are not logarithmic yet, thus indicating transient dynamics and not the ultimate regime of thermal convection.
- Subjects :
- JFM Papers
Convective heat transfer
Prandtl number
UT-Hybrid-D
FOS: Physical sciences
Settore ING-IND/06
01 natural sciences
010305 fluids & plasmas
Physics::Fluid Dynamics
symbols.namesake
0103 physical sciences
heat transfer
Rayleigh–Bénard convection
010306 general physics
Couette flow
Physics
Turbulence
Mechanical Engineering
Rayleigh-Bénard convection
Fluid Dynamics (physics.flu-dyn)
Reynolds number
Physics - Fluid Dynamics
Mechanics
Condensed Matter Physics
Nusselt number
turbulent convection
Boundary layer
Mechanics of Materials
Heat transfer
symbols
Subjects
Details
- Language :
- English
- ISSN :
- 00221120
- Database :
- OpenAIRE
- Journal :
- Journal of fluid mechanics, 897:A22. Cambridge University Press, Journal of Fluid Mechanics
- Accession number :
- edsair.doi.dedup.....d89e9a42b484407431b2f2dc2c32eec5