ABSTRACT
ABSTRACT: The flow effects on Brownian motion of nanoparticle suspensions are measured by back scattering diffusing wave spectroscopy (CCD-DWS). At 1% weight concentration, a series of experimental studies were carried out for different flow velocities in two flow cells: 1 mm by 1 mm and 3 mm by 3 mm cross sections, respectively. First, in static conditions where only Brownian motions exist, the autocorrelation functions of natural particles were obtained. As flow velocity increased, it was found that the autocorrelation functions started to change slightly when the Peclet number (Pe = U/k0D) reached about 29. Further flow velocity increase caused significant reduction in the slopes of the autocorrelation curves. The effects of Brownian motion persisted approximately up to Peclet number = 187. The above classifications clearly indicated the regions dominated by Brownian motion and flow motion respectively, as well as the transition.
