Averaging of particle data from phase Doppler anemometry in unsteady two-phase flow: Validation by numerical simulation

A novel post-processing algorithm is proposed to correct statistical bias observed in the treatment of time series obtained by a phase Doppler anemometer (PDA) at flow locations with variable particle velocity and concentration. Extensive properties of each validated particle are weighted with their inverse measuring (validation) volume to account for the procedure of particle sampling and fluctuations in the particle concentration. To compensate for the short characteristic length of the validation volume, the properties of particles are expressed by properties of fields of particle groups, using a local averaging time. A window shift and a decorrelation scheme are applied on the fields to increase their frequency resolution. This algorithm has been tested on numerical time series, provided by an Eulerian/Lagrangian code representing a gas/solids flow past a bluff body. Moments and spectral estimates of concentration and velocity of particle groups were successfully validated by the numerical simulation using the PDA data algorithm and control volume averaging. The control volume was much larger than the PDA validation volume, but the centre positions of the two volumes were identical.