Natural Convection, Heat Transfer, Natural Ventilation and Cooling

Buoyancy driven flows are common through our built environment and in most industrial processes where heat is exchanged. These flows include natural convection boundary layers, thermal plumes and positively and negatively buoyant jets. Many of the fundamental mechanisms that govern the behaviour of these flows are poorly understood. Improved understanding will lead to increased energy efficiency and better design and modelling tools. Our group has a long history of investigating these flows through large-scale direct numerical solution of the Navier-Stokes equations and laboratory experiments. We have a wide range of active projects. A brief overview of these is presented below. Applications for our PhD program are welcome.

The work is supported by the following recent ARC discovery project grants:

DP130100900, LP100100612, DP0988402, DP0664524, DP0988402, DP0556529, DP160102134.



Natural convection boundary layers:

The formation and development of natural convection boundary layers from steady low Rayleigh number flow through transition to fully turbulent flow is an area of strong interest in our group. Many of the important features of this basic flow are poorly understood. Of particular interest are the transition behaviour and heat transfer characteristics of these flows. In this work we rely primarily on large-scale direct numerical solution of the Navier-Stokes equations. We work with collaborators in Australia and overseas who provide an experimental perspective to this work.

The work is supported by the following recent ARC discovery project grants:

DP130100900: Conjugate natural convection boundary layers

DP0988402: Investigation and optimization of displacement ventilation and cooling

DP0664524: Stability, transition and heat transfer in thermally coupled natural convection boundary layers

Selected Publications:

Williamson, N., Armfield, S., Kirkpatrick, M. (2012). Transition to oscillatory flow in a differentially heated cavity with a conducting partition. Journal of Fluid Mechanics, 693(25 February 2012), 93-114.

Aberra, T., Armfield, S., Behnia, M., McBain, G. (2012). Boundary layer instability of the natural convection flow on a uniformly heated vertical plate. International Journal of Heat and Mass Transfer, 55(21-22), 6097-6108.

McBain, G., Chubb, T., Armfield, S. (2009). Numerical solution of the Orr-Sommerfeld equation using the viscous Green function and split-Gaussian quadrature. Journal of Computational and Applied Mathematics, 224(1), 397-404

McBain, G., Armfield, S., Desrayaud, G. (2007). Instability of the buoyancy layer on an evenly heated vertical wall. Journal of Fluid Mechanics, 587, 453-469.


Convective Free Shear Flows: Plumes, Buoyant Jets and Fountains

Thermal plumes and buoyant jets form in many heating and ventilation applications and also in environmental contexts. The turbulent exchange of heat, momentum and mass with the surrounding fluid dictates the evolution of the flow. The unknown dependence of these fluxes on the flow is a key uncertainty and limitation on current modelling. A current focus of our work is to understand the characteristics of the turbulent exchange flow. In this work our group uses our research computational fluid dynamics codes to perform large-scale direct numerical solution of the Navier-Stokes equations. We also obtain experimental results through our environmental fluid mechanics laboratory.

The work is supported by the following recent ARC discovery project grants:

DP0988402: Investigation and optimization of displacement ventilation and cooling

DP0556529: Turbulent fountains in stratified fluids with opposing buoyancy flux

DP160102134: Entrainment and Mixing in Turbulent Negatively Buoyant Jets and Fountains

Selected Publications:

Hattori, T., Norris, S., Kirkpatrick, M., Armfield, S. (2013). Prandtl number dependence and instability mechanism of the near-field flow in a planar thermal plume. Journal of Fluid Mechanics, 732, 105-127.

Williamson, N., Armfield, S., Lin, W. (2011). Forced turbulent fountain flow behaviour. Journal of Fluid Mechanics, 671, 535-558.

Williamson, N., Armfield, S., Lin, W. (2010). Transition behaviour of weak turbulent fountains. Journal of Fluid Mechanics, 655, 306-326.

Williamson, N., Nagarathinam, S., Armfield, S., McBain, G., Lin, W. (2008). Low-Reynolds-number fountain behaviour. Journal of Fluid Mechanics, 608, 297-317.


Natural Ventilation and Cooling and HVAC

The use of buoyancy due to varying air density within a building to drive ventilating flow is attractive from an energy efficiency perspective. A primary difficulty in modelling these flows is the dependence of the density field on the flow itself. An understanding of the turbulent exchange of mass and momentum is critical to making accurate model predictions. Our group works to understand these mass and momentum exchanges and also develop simple models of the internal flow within a naturally ventilated building. This work has both a fundamental and applied focus.

The work is supported by the following recent ARC project grants:

LP100100612: Design tools for optimizing data centre layout to minimize energy usage

DP0988402: Investigation and optimization of displacement ventilation and cooling