Detailed measurements in a swirling particulate two-phase flow by a phase-Doppler anemometer

The particle dispersion characteristics in a confined swirling flow with a swirl number of 0.47 have been studied in detail by applying the phase-Doppler technique, which allows the measurement of particle size and velocity. Furthermore, simultaneous measurement of the gas velocity was performed with some improvements in the data processing technique that allowed the gas velocity in presence of the dispersed phase to be obtained. From the particle velocity and size measurements the behavior of different sized classes out of the whole size spectrum ranging from about 20 to 80 μm could be studied, and the response of the particles to the mean flow and the fluid turbulence could be characterized. As a result of the complexity of the flow field and the very different time scales involved, the particle behavior was found to be a result of different phenomena. Due to the combined action of turbulent diffusion, radial particle transport, and centrifugal forces exerted on the particles, a separation of the particle phase was observed, resulting in a streamwise increasing particle mean number diameter in the core region of the flow.