Abstract
We investigate the counter-intuitive initial decrease and subsequent increase in the Nusselt number with increasing wall Reynolds number in the sheared Rayleigh-Bénard (RB) system by studying the energy spectra of convective flux and turbulent kinetic energy for Rayleigh number, Prandtl number and inverse Richardson numbers. These energy spectra show two distinct high-energy regions corresponding to the large-scale superstructures in the bulk and small-scale structures in the boundary layer (BL) regions. A greater separation between these scales at the thermal BL height correlates to a higher and indicates that the BLs are more turbulent. The minimum, which occurs at, is accompanied by the smallest separation between the large- and small-scale structures at the thermal BL height. At, we also observe the lowest value of turbulent kinetic energy normalized with the square of friction velocity within the thermal BL. Additionally, we find that the domain size has a limited effect on the heat and momentum transfer in the sheared RB system as long as the domain can accommodate the small-scale convective structures at the thermal BL height, signifying that capturing the large-scale superstructures is not essential to obtain converged values of and shear Reynolds number. When the domain is smaller than these small-scale convective structures, the overall heat and momentum transfer reduces drastically.
Original language | English |
---|---|
Article number | A1 |
Journal | Journal of fluid mechanics |
Volume | 944 |
Early online date | 22 Jun 2022 |
DOIs | |
Publication status | Published - 10 Aug 2022 |
Keywords
- Fluid mechanics
- Fluid dynamics
- turbulence
- direct numerical simulations
- High performance computing
- heat transfer
- Rayleigh Benard
- Convection
- shear flow
- UT-Hybrid-D