EPSRC Reference: 
EP/V047388/1 
Title: 
NonOberbeckBoussinesq Effects in the Ultimate State of Rapidly Rotating RayleighBenard Convection 
Principal Investigator: 
Horn, Dr S 
Other Investigators: 

Researcher CoInvestigators: 

Project Partners: 

Department: 
Ctr for Fluid and Complex Systems 
Organisation: 
Coventry University 
Scheme: 
New Investigator Award 
Starts: 
01 September 2021 
Ends: 
30 April 2024 
Value (£): 
235,863

EPSRC Research Topic Classifications: 
Continuum Mechanics 
Nonlinear Systems Mathematics 
Numerical Analysis 


EPSRC Industrial Sector Classifications: 
No relevance to Underpinning Sectors 


Related Grants: 

Panel History: 

Summary on Grant Application Form 
Many of the turbulent flows occurring in nature, for example within planetary and stellar interiors, as well as atmospheres, are driven by convection and are strongly constrained by rapid rotation.
An excellent and mathematically easily describable model system is rotating RayleighBénard convection. The model consists of a liquid or gas confined between a warm bottom boundary and a cold top boundary rotated around the vertical axis. But the level of turbulence and the relative rotation rates (expressed in terms of the control parameters Rayleigh and Ekman number) reached in earthbound numerical simulations and laboratory experiments of RayleighBénard convection, are not as extreme (yet) as the parameters in natural settings. Moreover, most numerical simulations and mathematical theories assume constant material properties (e.g. viscosity and thermal diffusivity), contrary to realistic fluids where they vary with temperature and pressure. Thus, interpreting results from simulations and experiments in the light of geophysical and astrophysical flows is somewhat problematic.
However, there is a longheld tenet in turbulence research that if the flow only becomes turbulent enough, that is, reaches the "ultimate regime," any global transport and macroscopic features become independent of the molecular diffusivities, in particular, the viscosity and the thermal diffusivity. Hence, crucially, if the ultimate state exists, an upscaling from numerical simulations and laboratory experiments to geo and astrophysical systems is possible despite many orders of magnitude difference in the control parameters.
The objective of the proposed research is to test the hypothesis of a diffusionfree scaling of the heat and momentum transport in the ultimate state of rapidly rotating RayleighBénard convection.
Even though theoretical arguments predict that the ultimate state is more easily accessible in rotating than in nonrotating systems, the numerical resolution requirements are prohibitive for a brute force approach with presentday computational resources.
To alleviate the resolution constraints, I will consider a novel point of view by employing a varying thermal diffusivity and kinematic viscosity within the very same convection vessel.
The variation of the material properties leads to a breaking of the topbottom symmetry in the classical (nonultimate) RayleighBénard problem. However, in the ultimate regime, one may expect that this symmetry gets restored, assuming that the molecular diffusivities do no longer affect the global flow state. The restoration of this symmetry can be used as an indicator and quantitative measure for reaching the ultimate regime and allows for reliable extrapolation.
Further, as boundary layers are known to be key players in the transport of heat and momentum in turbulent thermal convection, I will compare simulations of boundary layer free triply periodic RayleighBénard convection with laboratorylike cylindrical setups that include boundary layers.

Key Findings 
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk

Potential use in nonacademic contexts 
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk

Impacts 
Description 
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk 
Summary 

Date Materialised 


Sectors submitted by the Researcher 
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk

Project URL: 

Further Information: 

Organisation Website: 
http://www.cov.ac.uk 