Paper Anemometer Team Taiwan

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?

Problem Analysis Two qualities of sound may be considered: – Frequency – Strength Decibel Sensor Microphone

Experimental Setup

Metal Wire Wind Blower Voltage Regulator

Experimental Setup 4 cm 20 cm 3.3 cm Spaced Double Merged Double

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.

Experiment: Frequency Chart 1.The frequency spectrum of the noise made by the flapping paper

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

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

Experiment: Intensity Chart 1.Finding the optimum paper length for experiment Optimal Range

Experiment: Intensity Chart 3.The relationship between flow velocity and decibels measured when using different lengths of paper

Experiment: Intensity Chart 4.The relationship between flow velocity and decibels measured when using different arrangements of 15 cm paper strips.

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

Matching with Theory

Experimental results matches well with theory Deviations seen more often at lower wind velocities

Matching with Theory Table 1.Deviation of theoretical prediction from experimental results 15cm Single Paper dBV (m/s)Predicted (m/s)Deviation (m/s)Deviation % % % % % % AVG3.17%

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.

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.