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Classical 1/3 scaling of convection holds up to Ra = 10¹⁵.

ABSTRACT: The global transport of heat and momentum in turbulent convection is constrained by thin thermal and viscous boundary layers at the heated and cooled boundaries of the system. This bottleneck is thought to be lifted once the boundary layers themselves become fully turbulent at very high values of the Rayleigh number [Formula: see text]-the dimensionless parameter that describes the vigor of convective turbulence. Laboratory experiments in cylindrical cells for [Formula: see text] have reported different outcomes on the putative heat transport law. Here we show, by direct numerical simulations of three-dimensional turbulent Rayleigh-Bénard convection flows in a slender cylindrical cell of aspect ratio [Formula: see text], that the Nusselt number-the dimensionless measure of heat transport-follows the classical power law of [Formula: see text] up to [Formula: see text] Intermittent fluctuations in the wall stress, a blueprint of turbulence in the vicinity of the boundaries, manifest at all [Formula: see text] considered here, increasing with increasing [Formula: see text], and suggest that an abrupt transition of the boundary layer to turbulence does not take place.

SUBMITTER: Iyer KP

PROVIDER: S-EPMC7149414 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Classical 1/3 scaling of convection holds up to Ra = 10<sup>15</sup>.

Iyer Kartik P KP Scheel Janet D JD Schumacher Jörg J Sreenivasan Katepalli R KR

Proceedings of the National Academy of Sciences of the United States of America 20200325 14

The global transport of heat and momentum in turbulent convection is constrained by thin thermal and viscous boundary layers at the heated and cooled boundaries of the system. This bottleneck is thought to be lifted once the boundary layers themselves become fully turbulent at very high values of the Rayleigh number [Formula: see text]-the dimensionless parameter that describes the vigor of convective turbulence. Laboratory experiments in cylindrical cells for [Formula: see text] have reported d ...[more]

PMID: 32213591

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Project description:Radium isotopes have traditionally been used as tracers of surface and underground fresh waters in land-ocean interactions. The concentration of these isotopes is most effective on sorbents containing mixed oxides of manganese. During the 116 RV Professor Vodyanitsky cruise (22 April-17 May 2021), a study about the possibility and efficiency of 226Ra and 228Ra recovery from seawater using various types of sorbents was conducted. The influence of seawater flow rate on the sorption of 226Ra and 228Ra isotopes was estimated. It was indicated that the Modix, DMM, PAN-MnO2, and CRM-Sr sorbents show the best sorption efficiency at a flow rate of 4-8 column volumes per minute. Additionally, the distribution of biogenic elements (dissolved inorganic phosphorus (DIP), silicic acid, and the sum of nitrates and nitrites), salinity, and 226Ra and 228Ra isotopes was studied in the surface layer of the Black Sea in April-May 2021. Correlation dependencies between the concentration of long-lived radium isotopes and salinity are defined for various areas of the Black Sea. Two processes control the dependence of radium isotope concentration on salinity: conservative mixing of riverine and marine end members and desorption of long-lived radium isotopes when river particulate matter meets saline seawater. Despite the high long-lived radium isotope concentration in freshwater in comparison with that in seawater, their content near the Caucasus shore is lower mainly because riverine waters meet with a great open seawater body with a low content of these radionuclides, and radium desorption processes take place in an offshore area. The 228Ra/226Ra ratio derived from our data displays freshwater inflow spreading over not only the coastal region, but also the deep-sea region. The lowered concentration of the main biogenic elements corresponds to high-temperature fields because of their intensive uptake by phytoplankton. Therefore, nutrients coupled with long-lived radium isotopes trace the hydrological and biogeochemical peculiarities of the studied region.

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Classical 1/3 scaling of convection holds up to Ra = 10¹⁵.

Publications

Classical 1/3 scaling of convection holds up to Ra = 10<sup>15</sup>.

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Classical 1/3 scaling of convection holds up to Ra = 1015.

Publications

Classical 1/3 scaling of convection holds up to Ra = 10<sup>15</sup>.

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OmicsDI is part of the ELIXIR infrastructure

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Classical 1/3 scaling of convection holds up to Ra = 10¹⁵.