Moderate spatial confinement enhances the heat transfer in turbulent Rayleigh-Bénard (RB) convection [Chong et al., PRL 115, 264503 (2015)]. Here, by performing direct numerical simulations, we answer the question how the shape of the RB cell affects this enhancement. We compare three different geometries: a box with rectangular base (i.e., stronger confined in one horizontal direction), a box with square base (i.e., equally confined in both horizontal directions), and a cylinder (i.e., symmetrically confined in the radial direction). In all cases the confinement can be described by the same confinement parameter Γ-1, given as height-over-width aspect ratio. The explored parameter range is 1≤Γ-1≤64, 107≤Ra≤1010 for the Rayleigh number, and a Prandtl number of Pr=4.38. We find that both the optimal confinement parameter Γ-1opt for maximal heat transfer and the actual heat transfer enhancement strongly depend on the cell geometry. The differences can be explained by the formation of different vertically-coherent flow structures within the specific geometries. The enhancement is largest in the cylindrical cell, owing to the formation of a domain-spanning flow structure at the optimal confinement parameter Γ-1opt.
Hartmann, R., (Kai Leong), C., Stevens (Richard, J., Verzicco, R., Lohse, D. (2021). Heat transport enhancement in confined Rayleigh-Bénard convection feels the shape of the container. EUROPHYSICS LETTERS, 135(2) [10.1209/0295-5075/ac19ed].
Heat transport enhancement in confined Rayleigh-Bénard convection feels the shape of the container
Roberto Verzicco;
2021-01-01
Abstract
Moderate spatial confinement enhances the heat transfer in turbulent Rayleigh-Bénard (RB) convection [Chong et al., PRL 115, 264503 (2015)]. Here, by performing direct numerical simulations, we answer the question how the shape of the RB cell affects this enhancement. We compare three different geometries: a box with rectangular base (i.e., stronger confined in one horizontal direction), a box with square base (i.e., equally confined in both horizontal directions), and a cylinder (i.e., symmetrically confined in the radial direction). In all cases the confinement can be described by the same confinement parameter Γ-1, given as height-over-width aspect ratio. The explored parameter range is 1≤Γ-1≤64, 107≤Ra≤1010 for the Rayleigh number, and a Prandtl number of Pr=4.38. We find that both the optimal confinement parameter Γ-1opt for maximal heat transfer and the actual heat transfer enhancement strongly depend on the cell geometry. The differences can be explained by the formation of different vertically-coherent flow structures within the specific geometries. The enhancement is largest in the cylindrical cell, owing to the formation of a domain-spanning flow structure at the optimal confinement parameter Γ-1opt.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.