Airflow through the human nose is more complicated than that over a jumbo jet’s wing

Jan 5 2005

Winter colds can give you a blocked up nose that stops you smelling chimney smoke, roasting chestnuts, warming winter puddings and the other seasonal scents.

Now researchers funded by the Biotechnology and Biological Sciences Research Council (BBSRC) have not only discovered how air moves through the nose bringing you those smells but their work may lead to new ways of unblocking it and helping you to breathe more easily. They have even found that the airflow through the human nose is more complicated than that over a jumbo jet’s wing.

The scientists at Imperial College London have combined biological mechanics and aeronautical engineering to construct transparent 3D models of the nose. By running water or a special refractive-index-matched fluid through the models they have been able to map the flow pattern through the nasal cavity to work out where air goes when you breathe in. Tiny coloured beads circulate through the model nose to simulate airflow and this is captured on fast digital cameras. Professor Bob Schroter who jointly leads the research said, “From quiet breathing to rapid sniffing, we want to know exactly what is happening.”

The fluid dynamics of the nose is one of the most complex in the body, even more so than the flow of blood through the heart, with anatomical structures that cause eddies, whirls and recirculation.

Dr Denis Doorly, the other principal researcher, said, “People are used to the flows around an aeroplane being complicated but that is in some ways simpler than understanding the flows inside the nose. The geometry of the nose is highly complex, with no straight lines or simple curves like an aircraft wing and the regime of airflow is not simply laminar or turbulent.”

The research has mapped the flow of air around anatomical landmarks in the nose, such as the conchae and has discovered why we need to breathe deeply to smell a flower. Our sense of smell relies on a sample of air reaching the olfactory bulb at the top of the nose and that requires a sharp breathe and a high velocity shot of air to reach it. The Imperial scientists have found that the geometry of the nose causes the air to eddy around in the vicinity of the bulb so you can smell the flower.

The research is a significant step forward from what had been learned about the nose from studying cadavers and animals, and may soon be helping surgeons plan their operations and drug companies to develop new ways of delivering drugs through the nose straight into the bloodstream – as well as new products to unblock the nose.