Using ultrasonic Doppler velocimetry and CFD modeling to investigate the mixing of non-Newtonian fluids possessing yield stress

Investigation of Mixing in Shear Thinning Fluids Using Computational Fluid Dynamics

“…Γ has negligible effect on the tracer distribution possibly because the insignificant contribution of molecular diffusion to the overall tracer dispersion (Montante et al, 2005). Some researchers also find that the effect of the molecular diffusivity is negligible in the mixing of non-Newtonian fluids in the laminar regime Ihejirika & Ein-Mozaffari, 2007;Ein-Mozaffari & Upreti, 2009). Pakzad (2007) used CFD to predict the mixing time for the agitation of the shear-thinning fluid possessing yield stress with a Scaba 6SRGT impeller.…”

“…For the mixing of shear-thinning fluids with yield stress, CFD model validation is typically done by comparing the CFD-predicted power number, and velocity field with the experimental counterparts (Ihejirica & Ein-Mozaffari, 2007;Saeed et al, 2007;Pakzad et al, 2008b;Ein-Mozaffari & Upreti, 2009). Figure 2 depicts the impeller power number as a function of Reynolds number (Re) for the Lightnin A200 impeller in the mixing of xanthan gum solution, which is a shear-thinning fluid with yield stress .…”

“…To experimentally determine the velocity field, Ultrasonic Doppler Velocimetry (UDV) has been effectively used in the mixing of shear-thinning fluids with yield stress using different impellers (Ein-Mozaffari et al, 2007a, Ihejirika & EinMozaffari, 2007Pakzad et al, 2008b;Ein-Mozaffari & Upreti, 2009). UDV is a non-invasive method of measuring velocity profiles (Asher, 1983), which is very useful in industrial applications.…”

Determining the viscous behavior of non-Newtonian fluids in a flume using a laminar sheet flow model and Ultrasonic Velocity Profiling (UVP) system

“…UVP is accepted as an important tool for measuring flow ABCM profiles in opaque liquids in research and engineering and it has been previously applied in complex geometries such as stirred tanks (Bouillard et al, 2001;Ein-Mozaffari and Upreti, 2009), contractions (Ouriev and Windhab, 2003;Kotzé et al, 2011), liquid metal target of neutron spallation source configuration (Takeda and Kikura, 2002), cylindrical hydrocyclone (Bergström and Vomhoff, 2004) as well as diaphragm valves (Kotzé et al, 2011). This highly versatile technique can also be used to determine fluid properties such as concentration profiles (Sad Chemloul et al, 2009), solid particle velocity as well as rheological properties.…”

The influence of system scale on impinging jet sediment erosion: Observed using novel and standard measurement techniques

“…Here we demonstrate a new non-intrusive methodology using ultrasonic velocity profiling (UVP), for measuring the dynamic scour depth at a frequency of up to 128 Hz, enabling both the maximum depth to be measured and the steady-state time-scale to be calculated. Such Doppler profilers are widely used for measuring flow in pipes and channels (Baas et al, 2009;Birkhofer et al, 2008;Harbottle et al, 2011;Kantoush et al, 2008;Kotze et al, 2011), assessing the performance of tank mixing systems (EinMozaffari et al, 2007;Ein-Mozaffari and Upreti, 2009;Mali and Patwardhan, 2009), and can be used for analysing the consolidation of free-settling coagulated suspensions (Hunter et al, 2011b).…”