3B SCIENTIFIC PHYSICS 8404300 Instrucciones De Uso página 5

3. Operating principle
As a result of the small gap between the glass
plates, an almost entirely uniform flow of air is
created in the space between the glass plates.
The course of the air flow is demonstrated by the
woollen threads. Initially, the threads are equidis-
tant and run parallel to one another.
If any obstacles are introduced into the air flow,
then the air flows sideway around the body making
the woollen threads change their position.
Changes in the velocity of the air flow are also
demonstrated by the threads. The closer the
threads are to one another, the greater the velocity
of the flow.
4. Operation
Required accessories:
1 Air blower with hose
1 Overhead projector (recommended)
•
Place the air flow apparatus on the overhead
projector.
The woollen threads run parallel to one another.
•
Connect the jet of the blower to the inlet of the
air flow apparatus via the hose.
•
Switch on the overhead projector.
•
Switch on the blower.
•
Adjust the air flow so that the ends of the
threads do not begin to vibrate.
If the air pressure is too low, it is not possible to
demonstrate the proper course of the air flow.
•
Place the desired aerodynamic body in a cen-
tral position between the two glass plates.
•
Gently shift the aerodynamic body to prevent
the threads from getting entangled.
•
The air flow splits and goes around the flow
body. The threads show the course of the air
flow in front of and behind the flow body.
•
When the desired result has been obtained,
switch off the blower.
The threads remain in their final position.
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5. Sample experiments
5.1 Course of flow in the case of a linear laminar
flow
In the case of linear laminar flow, all flow lines are
parallel. The direction and flow velocity are equal
at all points of the air flow.
5.2 Course of flow along a teardrop-shaped body
When the air flow moves around a teardrop-shaped
body, the flow lines narrow around the body itself.
The velocity of flow also increases. Once the flow
passes the body, the flow velocity reduces.