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PROFESSOR: So in the
last part of the course,

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we'll discuss the fluid
mechanics of indoor spaces,

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in particular, going
beyond the approximation

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of a well-mixed room when
considering airborne disease

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transmission.

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So for example, we will
consider the occupants

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of a room and their
respiratory activity.

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So when they breathe, especially
if they're not wearing a mask,

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or if they cough, they're
going to have turbulent plumes

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emitting from their
mouth, which will then

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be convected throughout
the room and will influence

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other people.

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Also, the heat of the
body relative to the room

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can lead to warmer air, which
is rising, so that essentially

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sort of a chimney
of a thermal plume

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rising from an individual.

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Those heterogeneities
in the flow

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and in the concentration
of aerosol particles

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may not always be well-mixed.

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We'll talk about different
types of ventilation,

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how, for example, cold air
will sink from the place

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where it's inserted
and warm air will rise.

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And that may or may
not lead to sufficient

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mixing to remain well-mixed.

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And we'll talk about how
to modify our criterion

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for airborne
disease transmission

27
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in a well-mixed room to account
for some of these changes,

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in particular the heightened
risk of short-range

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transmission from being
directly in the path

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of respiratory puffs
and plumes emanating

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from an infected person.