3B Scientific Water Wave Channel User Manual
3B SCIENTIFIC
Water Wave Channel 1000807
Instruction sheet
05/12 ELWE/ALF
®
PHYSICS
1. Description
The water wave channel serves for the demonstration and investigation of surface waves in water.
It consists of a large transparent oblong trough,
which is two-thirds filled with water.
The waves are produced in the short V-shaped
section and studied in the I-shaped section. For the
generation of the waves a motor with transmission
is attached at the end of the V-shaped channel. It
propels two wave exciters, which move up and
down in the water. Each exciter produces a wave in
a section of the V-shaped channel. Depending
upon the setting, the two exciters can move in the
same direction or in contra motion. The frequency
of these waves can be varied by changing the operating voltage of the motor.
In both partial channels there is a frame with a
fleece directly in front of the wave exciters which
the waves must pass through. Thus to a large extent a sinusoidal process is achieved. Then the
waves enter the I-shaped part of the channel and
move along to its end. If the absorbing frame with
fleece is introduced at the end of this channel,
then they are dissipated as far as possible. Thus a
continuous wave pattern develops in the channel.
If the absorber is not inserted, the waves travel to
the end of the I-shaped channel and are reflected.
With a short switch-on time of the motor, a wave
train develops which travels through the channel
and is reflected and travels back towards the exciter. With continuous operation of the motor the
arriving and the reflected waves overlap, producing
an image of a motionless standing wave.
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If the wave absorbed at the end of the I-channel is
produced by only one wave exciter (by blocking the
second partial channel), then its amplitude is
small. If both partial waves arrive into the I-shaped
part of the channel, then the amplitude increases.
By inserting the separator into the transient area
between the V-shaped channel and the I-shaped
channel, the two partial waves run separately in
the I-shaped channel and their motions can be
compared with one another. If the two wave exciters are operated in contra motion then the phase
shift from λ/2 can be clearly observed in the area
of the inserted glass plate. The overlap of these two
partial waves leads to the fact that after they enter
the rear part of the I-channel they cancel each
other out to the greatest extent possible.
The following experiments can be carried out with
the water wave channel:
Production of a non-periodic wave
Production of a periodic wave
Proof that waves transport energy, but not material
Phase and group velocity of a wave
Determination of the phase velocity
Demonstration of the relationship between frequency and wavelength
Reflection of a wave
Standing waves
Same-phase overlapping of waves
Overlapping of waves with a phase shift of λ/2
1.1 Accessories
2 Frames with fleece for the homogenisation of
the waves (primary absorber)
1 Frame with fleece for the supression of the
wave reflection at the end of the channel (secondary absorber)
1 Tube for the temporary blocking of a partial
channel
1 Transparent separator 40x170x6 mm
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with
spacer pieces for inserting into the I-shaped
channel
2 Plastic balls with thread for the proving the up
and down movement
1.2 Additionally required apparatus
1 Power supply unit for DC voltage, 0 ... 20 V,
continuously variable
1 Reflector lamp
Fluoreszein for colouring the water
2. Technical data
Operating voltage of motor: 12 V DC
Dimensiones: 1500 mm x 150 mm x 290 mm
Mass: approx. 12.6 kg
3. Operation
• Fill up the water wave channel to the marked
height with water, to which some fluoreszein
has been added (fig. 1).
• The lighting with the reflector lamp takes place
diagonally from above, so that a fluorescent
layer appears on the water surface.
• Connect the motor to the power supply unit.
• Into the two partial channels of the V-shaped
part, a conical frame with fleece is introduced.
• At the end of the I-shaped part, the absorber
frame with fleece is introduced at such an angle that the waves at the surface travel very
flatly over it.
• Switch on the motor.
The image of a spreading wave develops.
In order to change the phase position of the two
partial waves, one of the rollers on the wave exciter
is rotated through 180° until it engages.
The voltage for the motor can be increased briefly
to approximately 13 V. The amperage is smaller
than 0.5 A. The switch for the motor has three
positions. In the middle position the motor is
switched off. When pressed to one side, the motor
is switched on and remains on until the switch is
returned to the off position (continuous mode).
When pressed in the other direction, the motor is
switched on and remains on only whilst pressure is
maintained (pulse mode). In this mode short wavelengths can be produced.
• When the experiments are completed put a
water bucket under the end of the I-shaped
channel.
To empty the channel a fatigue proof plastic tube
connected to the channel inside is stored in the
grey box at the end of the channel.
• To drain the water, carefully take the tube out
of the box (one end is fixed to the drain noz-
zle).
• Slightly strech the tube and place the free end
into the bucket.
The water will be drained automatically.
• After draining the channel fold the tube in its
original zigzag configuration and push it back
into the box.
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