Measurement tools and techniques

The Wind Energy Group is strongly involved in experimental fluids research, and therefore we are well-equipped with experimental measurement tools. Some of the most advanced equipment available are for laser Doppler velocimetry and particle image velocimetry, which are both non-intrusive, optical measurement techniques.

Laser Doppler velocimetry

LDV is a technique for measuring the velocity of a fluid at a point. Two beams of laser light are crossed at the measurement point, creating a simple interference pattern. The fluid is seeded with tiny particles, which reflect light into a photodetector as they pass through the fringes of constructive interference. A computer analyzes the frequency of the light reflections, and then, knowing the fringe spacing, calculates a component of velocity of the fluid at that point.

A complete, three-dimensional LDV system by Dantec Dynamics is available to us, and has been used several times in the past by students in the Wind Energy Group.

Particle image velocimetry

PIV is a technique for visualizing the two-dimensional velocity flow field in a fluid. The fluid is seeded with tiny particles, which are simultaneously illuminated by a sheet of laser light and photographed by a digital camera. The images are divided into numerous interrogation windows, and then two consecutive images are cross-correlated to estimate the displacement vectors of the particles. Knowing the time elapsed between the two images, the velocity vectors are easily calculated.

There are several research-class lasers available, including a dual-head, pulsed, Nd:YAG laser system by New Wave Research. As well, we have a CCD camera by Kodak, and a high speed CMOS camera by Photron.

Other equipment

Some other fluid measurement tools available include a sonic anemometer (which measures all three components of velocity at a point), a convenient handheld anemometer, and pressure transducers.