HEALTH
NASAL CAVITY
SIMULATION
Transient CFD of a complete
human respiration cycle
COLLABORATION
Carried out with medical professionals
CHALLENGE
Resolve a full inhalation and exhalation cycle through the nasal cavity, not a steady snapshot of one
RESULT
The airflow through a breath, in a form a surgeon can look at before operating
01
CHALLENGE
Breathing through the nose is a fluid dynamics problem that happens to be made of tissue. The geometry of the cavity sets the resistance, decides how the air distributes between the two sides, and conditions it — warming, humidifying and filtering it — before it reaches the lungs.
Which is why a nose can be changed surgically and breathe worse afterwards. Rhinoplasty and septal surgery alter exactly the geometry that governs the flow, and a result that is correct anatomically and pleasing aesthetically can still obstruct. Surgeons plan from anatomy, imaging and experience; what none of those show is what the air actually does.
Measuring it directly is close to impossible. The passage is narrow and convoluted, the instrument would disturb the flow it came to measure, and the flow is unsteady by nature — it accelerates, stops and reverses twice in every breath. A steady-state calculation of inhalation, which is the usual simplification, describes a condition that exists for a fraction of a second.
02
SOLUTION
We worked with medical professionals to model the inhalation and exhalation cycles of respiration with CFD — their anatomy and clinical judgement, our fluid dynamics.
The nasal cavity was reconstructed as a three-dimensional domain from imaging, sinuses included, and the simulation run transient over a complete respiration cycle: the mass flow follows the breathing waveform, so inhalation, the reversal at the top of the breath, exhalation and the second reversal are all resolved in sequence rather than assumed away.
What comes out is the velocity field through the whole cavity at every instant of the breath: where the air accelerates, which passage carries it, where it stagnates, and how the picture differs between breathing in and breathing out — which it does, considerably.
03
RESULTS
The analysis makes the invisible part of the operation visible. A surgeon can see how a given geometry actually breathes, and in principle compare one planned correction against another before the patient is on the table rather than after.
That is the value in this sector: not a prettier picture, but a way to check that a nose which will look right will also work right — and, where breathing is already obstructed, to understand why.
It is also a reminder of how far these methods travel. The same transient CFD that follows air through a compressor or an industrial building follows it through a nose, because the physics does not care what the duct is made of.