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Paper Anemometer
Team Taiwan
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Official Description
• Paper Anemometer• When thin strips of paper are placed in an air
flow, a noise may be heard. • Investigate how the velocity of the air flow can
be deduced from this noise?
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Problem Analysis
• Two qualities of sound may be considered:– Frequency– Strength
Decibel Sensor
Microphone
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Experimental Setup
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Experimental Setup
Metal Wire
Wind Blower
Voltage Regulator
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Experimental Setup
4 cm 20 cm3.3 cm
Spaced Double Merged Double
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Experiment
Wind velocity is adjusted with a voltage regulator, the input voltage and its corresponding wind velocity is measured.
Noise made by the paper is measured in decibels and recorded by a microphone.
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Experiment: Frequency
Chart 1.The frequency spectrum of the noise made by the flapping paper
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Experiment: Frequency
• No specific frequency is seen in the frequency spectrum of the noise
• Therefore, we will try to use the intensity of the noise to estimate the velocity of the wind
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Theory
• The sound intensity of a vortex interacting with a surface is proportional to the sixth power of the flow velocity
Source: Powell, Alan, Theory of Vortex Sound, The Journal of the Acoustical Society of America, January 1964
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Experiment: Intensity
Chart 1.Finding the optimum paper length for experiment
Optimal Range
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Experiment: Intensity
Chart 3.The relationship between flow velocity and decibels measured when using different lengths of paper
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Experiment: Intensity
Chart 4.The relationship between flow velocity and decibels measured when using different arrangements of 15 cm paper strips.
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Matching with Theory
• According to the theory, the intensity of the noise is proportional to the sixth power of the wind velocity.
• We will use to fit our experimental data
6v k I
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Matching with Theory
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Matching with Theory
• Experimental results matches well with theory• Deviations seen more often at lower wind velocities
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Matching with Theory
Table 1.Deviation of theoretical prediction from experimental results
15cm Single PaperdB V (m/s) Predicted (m/s) Deviation (m/s) Deviation %
79.00 6.80 7.08 -0.28 4.14%
82.60 8.30 8.13 0.17 2.04%
87.40 9.30 9.78 -0.48 5.11%
89.00 10.70 10.39 0.31 2.86%
90.50 11.20 11.01 0.19 1.69%
AVG 3.17%
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Using the Paper Anemometer
• Set up the experimental device with a paper strip and a decibel meter.
• Calibrate the device with air flows of different known velocities.
• Calculate the ratio k from the velocity-decibel relationship.
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Using the Paper Anemometer
• Blow on the paper strip with an air flow of unknown velocity and measure the sound pressure level.
• Convert decibels to sound intensity. Using the relationship , the velocity of the air flow may be obtained.
6v I