| Popis: |
Particle behaviour and the influence of particles in multiphase turbulent flows has been examined. The effects of particle size, density and volume fraction on both the particle and fluid phases of pipe flows and impinging jets have been measured. These systems were measured using a combination of ultrasonic Doppler velocimetry and particle image velocimetry with comparisons between the two techniques made. UDV was used to measure axial particle velocity and velocity fluctuations within a pipe at particle volume fractions between 1x10-4 and 64x10-4 using a 2MHz ultrasonic transducer. Particle density effects were examined by comparing 225μm glass Honite 12 particles with (ρ = 2450) with 225μm polystyrene Flashbead particles (ρ = 1050). Size effects were examined using 500μm glass Honite 8 particles. PIV was then used to examine the fluid response to increased particle loading within a pipe. Fluorescent tracer particles combined with an optical filter allowed for the solid phase to be excluded from the measurement. Particle volume fractions between 1x10-4 and 8x10-4 were examined using the same particles as before in addition to smaller 40μm glass Honite 22 particles. The influence of particles on fluid turbulence is examined in addition to velocities. The technique was then expanded to examine the more complicated flow regime of an impinging jet. In this case particle volume fractions were tested up to 4x10-4, the same range of particles was tested excluding the Honite 8 particles due to their size relative to the jet. The work is concluded with measurement of the solid phase using PIV and comparison of the effectiveness of various models for predicting enhancement or suppression of turbulent flow. |
