Estimation of turbulent velocity spectra from laser Doppler data

We review the problem of spectral estimation from velocity data sampled irr egularly in time by a laser Doppler anemometer (LDA) from very early estima tors based on slot correlation to more refined estimators, which build upon a signal reconstruction and an equidistant re-sampling in time. The discus sion is restricted to single realization anemometry, i.e. excluding multipl e particle signals. We classify the techniques and make an initial assessme nt before describing currently used methods in more detail. An intimately r elated subject, the simulation of LDA data, is then briefly reviewed, since this provides a means of evaluating various estimators. Using the expectat ion and variance as figures of merit, the advantages and disadvantages of s everal estimators for varying types of turbulent velocity spectral distribu tions are discussed. A set of recommendations is put forward as a conclusio n.