Pyroelectric anemometry: Vector and swirl measurements

The characteristics of a vector pyroelectric anemometer that measures the orthogonal components of mass flow are presented. This anemometer consists of three measuring electrodes and two heater elements on a 6 mm X 6 mm chip that form two orthogonal linear anemometers. The characteristics of a single pair of electrodes forming an in-line linear anemometer are in good agreement with recent measurements and theory. A wall-mounted vector pyroelectric anemometer is used to measure the decay of swirl in air flowing through a 45 mm inner diameter, 5 m long flow system. The swirl flow is produced by a 90 degrees out-of-plane double elbow at the flow system inlet. The tube flow generated by a squirrel-cage fan has a Reynolds number of approximate to 24 000, well into the turbulent regime. Measurements are conducted at the wall at a uniform distance along the length of the flow section for both straight and swirl flow. The measured decay length is approximate to 40 pipe diameters, in good agreement with measurements on water.