3B Scientific Air Flow Apparatus User Manual

3B SCIENTIFIC® PHYSICS

Air flow apparatus 8404300

Instruction sheet

08/06 SP

1 Aerodynamic bodies
2 Glass plates
3 Woollen threads
4 Air chamber
5 Air inlet

1. Description

The air flow apparatus is used to demonstrate air
flow patterns for objects of different shapes. The
flow patterns can be projected onto a wide screen
with an overhead projector.

26 woollen threads fastened at their ends at an
equal distance from one another are arranged
between two glass plates. The glass plates have a
gap of approximately 1 mm between them and are
sealed off lengthwise on both sides.

Air supplied by an external blower is initially intro­duced to the air chamber through the air inlet.
From the air chamber, the air flows into the empty
space between the two glass plates and exits into
the open from the opposite end.

The air chamber is equipped with a one-way valve
which prevents the air from flowing in the wrong
direction in case the air flow apparatus is con­nected to the suction nozzles of the blower by
mistake.

Aerodynamic bodies of different shapes can be
introduced into the air flow. The inserted bodies
can be positioned in the air flow from outside.

1.1 Scope of delivery

1 Air flow apparatus
1 Circular body
1 Rectangular body
1 Streamlined body
1 Wing section
2 Bodies to demonstrate narrowing of flow

2. Technical data

Air flow apparatus
Dimensions: 370 x 320 x 80 mm
Weight: 3 kg
Aerodynamic bodies
Circular body: 105 mm Ø
Rectangular body: 90 mm x 60 mm
Streamlined body: 160 mm x 80 mm
Wing section: 150 mm x 60 mm
Narrowing bodies: 150 mm x 65 mm

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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 equidis­tant 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 8404240
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.

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.

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