Tow Tank

The University of Maine has a 70 foot long tow tank located on campus at the Aqua culture Research Center. The tow tank is powered by and electric motor and can tow up to a speed of 6 ft/s or 4 mph. Below is a video that shows the tow tank running at a speed of 3 ft/s.

Testing

To test our anemometer it was mounted to the front of the tow tank trolley with two bolts.

After the anemometer was mounted the sensor was connected to the data acquisition system. The system contained a frequency to voltage converter. This system converts the frequency of the rotating propeller into a voltage that can be read by the data logging system. The speed of the tow tank is controlled by altering the frequency of the electric motor. The range of frequency of the motor is 0 - 60 Hertz. We tested from 5Hz to 50Hz in increments of 5Hz. The faster the tow tank moved, the fast the propeller spun, and a higher voltage was produced. This Excel Workbook is all the information recorded from testing. Here is a picture of the anemometer in the water.

Calibration

To calibrate the anemometer we had to measure the speed of the tow trolley. To measure the speed of the trolley a distance over time measurement was taken. The distance was 25 feet and the time it took the trolley to cover that distance after reaching constant speed was measured. This gave us the speed in ft/s of the trolley. The trolley ran at the same frequencies that we tested our anemometer at. With speed of the trolley known, voltage to speed relations could be made. The speed of the flow can now be calculated from the voltage out put from the data acquisition system.