A new look at particle statistics in laser-anemometer measurements

Many algorithms have been proposed and evaluated for dealing with laser-anemometer measurements in low particle densities since the original paper of McLaughlin & Tiederman (1973). All of them describe the effect of making a measurement whenever a particle is visible to the measurement instrument. However, in many circumstances, one wishes to sample the velocity at a constant rate–for instance, in measurement of velocity fluctuation spectra. It is shown here that the measurement statistics for this case are different from those previously discussed in the literature. The product of the particle density and the sample interval is the controlling parameter for the statistical description of the measurements. The asymptotic forms for low and high particle density-sample time products are derived.