The time-of-flight laser anemometer

The time of flight laser anemometer is based on measuring the time of flight between two small volumes in space by correlation techniques. It is shown that this anemometer can generally give the same kind of information as can be obtained with a laser Doppler anemometer, and that in some specific cases the space time resolution is even better than for the laser Doppler anemometer. The uncertainties on the measured values are discussed in relation to the statistical properties of the measuring system and signal processing. The effects of spatial and temporal velocity fluctuations are analyzed. With the anemometer it is possible to obtain a particle size versus particle velocity spectrum, provided that the particles are larger than the focal beam diameters in the flow direction. The anemometer was used for measurements in a two phase flow surrounding a simulated fuel rod. The configuration was also used under extremely low light level conditions (an average number of photon counts less than one per transit through one spot) to measure gas velocity.