Natural ventilation/architectural fluid mechanics

Temperature control and ventilation of modern buildings is a costly enterprise and accounts for a significant fraction of primary energy consumption in both the developed and developing world. "Naturally-ventilated" buildings seek to reduce this expense by harnessing freely-available resources such as solar radiation, wind shear and internal temperature gains due to building occupants, electrical equipment, etc. in forcing air into and out of the built environment. Although the aforementioned resources are free, they can be difficult to control. For example, as suggested by the following cartoon image, even relatively simple buildings forced by the wind and internal heat gains can exhibit multiple steady states and hysteresis. A major objective of my present research (conducted in large part with Colm P. Caulfield, Univ. of Cambridge) is to examine the details of this unexpected behavior when the thermal source is "non-ideal," i.e. it supplies both heat and mass to the interior space. This particular research interest is one piece of a much larger puzzle aimed at understanding how the principles of natural ventilation, originally developed for application in temperate climates, can be profitably extended to the wide seasonal variations of climate characteristic of Canada in general and Alberta in particular.

Also with Colm P. Caulfield (Univ. of Cambridge), I have sought to expand the geometric scope of idealized theoretical models by examining the ventilation behavior of multiply-connected buildings, which are meant to more faithfully represent the complicated internal geometry of most modern residential and office dwellings.

A down-draft cooling tower adorns the front of the Zion National Park Visitor's Center in Utah. The tower exploits evaporative cooling in maintaining comfortable interior conditions during hot summer months. (Photo credit: http://www.nrel.gov.buildings/)


The ventilation of a simple building in the presence of an adverse wind gradient. When the wind forcing is low, the flow regime is dominated by internal buoyancy and the interior space exhibits a vertical stratification of temperature. Conversely when the wind forcing is high, well-mixed internal conditions are predicted. Interestingly, both the wind- and buoyancy- dominated flow regimes may be stable for the same combination of parameters, leading to multiple steady states and hysteresis (cartoon adapted from Flynn & Caulfield, Building & Environment 44, 2009).


Recent (and not-so-recent) publications:
  • Natural vs. blocked ventilation in naturally ventilated buildings -- the effect of finite and decoupled sources (arXiv manuscript with V. Mayoraz) (link)

  • Buoyancy-driven exchange flow between two adjacent building zones connected with top and bottom vents (Building & Environment 92, with S. Nabi) (link)

  • Influence of geometric parameters on the eventual buoyancy stratification that develops due to architectural exchange flow (Building & Environment 71, with S. Nabi) (link)

  • The hydraulics of exchange flow between adjacent confined building zones (Building & Environment 59, with S. Nabi) (link)

  • The role of diffusion on the interface thickness in a ventilated filling box (J. Fluid Mech. 652, with N.B. Kaye, M.J. Cook and Y. Ji) (link)

  • Effect of volumetric heat sources on hysteresis phenomena in natural and mixed-mode ventilation (Building & Environment 44, with C.P. Caulfield) (link)

  • Natural ventilation in interconnected chambers (J. Fluid Mech. 564, with C.P. Caulfield) (link)

  • Transient blocking in multi-chamber natural ventilation (Proc. 6th Intl. Symposium on Stratified Flows, with C.P. Caulfield) (.pdf)