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Fluids 2017, 2(3), 41; doi:10.3390/fluids2030041

Regimes of Axisymmetric Flow and Scaling Laws in a Rotating Annulus with Local Convective Forcing

1
Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
2
Ecole Normale Supérieure de Lyon, Université de Lyon, CNRS, 46 Allée d’Italie, F-69364 Lyon CEDEX 07, France
3
Now at Université Grenoble Alpes, Institut des Sciences de la Terre, F-38000 Grenoble, France
*
Authors to whom correspondence should be addressed.
Received: 8 June 2017 / Revised: 14 July 2017 / Accepted: 16 July 2017 / Published: 19 July 2017
(This article belongs to the Collection Geophysical Fluid Dynamics)
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Abstract

We present a numerical study of axisymmetric flow in a rotating annulus in which local thermal forcing, via a heated annular ring on the outside of the base and a cooled circular disk in the centre of the top surface, drives convection. This new configuration is a variant of the classical thermally-driven annulus, where uniform heating and cooling are applied through the outer and inner sidewalls respectively. The annulus provides an analogue to a planetary circulation and the new configuration, with its more relaxed vertical thermal boundary conditions, is expected to better emulate vigorous convection in the tropics and polar regions as well as baroclinic instability in the mid-latitude baroclinic zone. Using the Met Office/Oxford Rotating Annulus Laboratory (MORALS) code, we have investigated a series of equilibrated, two dimensional axisymmetric flows across a large region of parameter space. These are characterized in terms of their velocity and temperature fields. When rotation is applied several distinct flow regimes may be identified for different rotation rates and strengths of differential heating. These regimes are defined as a function of the ratio of the horizontal Ekman layer thickness to the non-rotating thermal boundary layer thickness and are found to be similar to those identified in previous annulus experiments. Convection without rotation is also considered and the scaling of the heat transport with Rayleigh number is calculated. This is then compared with existing work on the classical annulus as well as horizontal and Rayleigh-Bénard convection. As with previous studies on both rotating and non-rotating convection the system’s behaviour is found to be aspect ratio dependent. This dependence is seen in the scaling of the non-rotating Nusselt number and in transitions between regimes in the rotating case although further investigation is required to fully explain these observations. View Full-Text
Keywords: rotating flow; convection; baroclinic flow; numerical modelling rotating flow; convection; baroclinic flow; numerical modelling
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Wright, S.; Su, S.; Scolan, H.; Young, R.M.B.; Read, P.L. Regimes of Axisymmetric Flow and Scaling Laws in a Rotating Annulus with Local Convective Forcing. Fluids 2017, 2, 41.

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