Reynolds number scaling and energy spectra in geostrophic convection
| Autor: | Matteo Madonia, Andrés J. Aguirre Guzmán, Herman J.H. Clercx, Rudie P.J. Kunnen |
|---|---|
| Přispěvatelé: | Fluids and Flows, EIRES Eng. for Sustainable Energy Systems, Transport in Turbulent Flows (Clercx), Turbulent and Multiphase Flows (Kunnen) |
| Jazyk: | angličtina |
| Rok vydání: | 2022 |
| Předmět: | |
| Zdroj: | Journal of Fluid Mechanics, 962:A36. Cambridge University Press J Fluid Mech |
| ISSN: | 0022-1120 |
| Popis: | We report flow measurements in rotating Rayleigh--B\'enard convection in the rotationally-constrained geostrophic regime. We apply stereoscopic particle image velocimetry to measure the three components of velocity in a horizontal cross-section of a water-filled cylindrical convection vessel. At a constant, small Ekman number $Ek=5\times 10^{-8}$ we vary the Rayleigh number $Ra$ between $10^{11}$ and $4\times 10^{12}$ to cover various subregimes observed in geostrophic convection. We also include one nonrotating experiment. The scaling of the velocity fluctuations (expressed as the Reynolds number $Re$) is compared to theoretical relations expressing balances of viscous--Archimedean--Coriolis (VAC) and Coriolis--inertial--Archimedean (CIA) forces. Based on our results we cannot decide which balance is most applicable here; both scaling relations match equally well. A comparison of the current data with several other literature datasets indicates a convergence towards diffusion-free scaling of velocity as $Ek$ decreases. However, the use of confined domains leads at lower $Ra$ to prominent convection in the wall mode near the sidewall. Kinetic energy spectra point at an overall flow organisation into a quadrupolar vortex filling the cross-section. This quadrupolar vortex is a quasi-two-dimensional feature as it only manifests in energy spectra based on the horizontal velocity components. At larger $Ra$ the spectra reveal the development of a scaling range with exponent close to $-5/3$, the classical exponent for inertial-range scaling in three-dimensional turbulence. The steeper $Re(Ra)$ scaling at low $Ek$ and development of a scaling range in the energy spectra are distinct indicators that a fully developed, diffusion-free turbulent flow state is approached, sketching clear perspectives for further investigation. Comment: 18 pages, 6 figures |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|