(596az) Characterizing Fluid Dynamics of Impinging Jet Mixing with Ultrasonic Excitation Using Particle Image Velocimetry

The development of reproducible pharmaceutical products is inherently attributed to the complex interactions between transport and mixing processes.  Quite often, failure to duplicate mixing behavior causes batch-to-batch variability.  Moreover, the improper scaling of these processes to varying batch size contributes to unpredictable outcomes.  There is a significant need in the pharmaceutical industry to study and model the fluid flow behavior and mixing characteristics of chemical reactions, and thereby establish reliable production methods.  Additionally, it is necessary to establish tools to characterize the impact of mixing variability during scaling.

A novel reaction chamber with impinging jet mixing and ultrasonic excitation was designed to aid in the development of a new pharmaceutical product.  A Particle Image Velocimetry (PIV) system was used to measure velocity profiles of the fluid flow while the effects of the ultrasonic excitation on the flow characteristics were studied.  Endoscopes were used to position the laser sheet and camera lens close to the centerline of the flow. A method to focus the camera on a small field of interest was developed, which allowed for accurate measurement of the velocity profiles. As the reactants in the pharmaceutical process studied are corrosive, water was used as a substitute medium in order to avoid damaging the imaging equipment. The flow was characterized at various volumetric flow rates and ultrasonic excitation intensity, as well as at various lengths away from the excitation source. From the flow fields, local shear rates were determined using the DaVis LaVision^® PIV imaging software. From shear rates, energy dissipation was characterized. Local energy dissipation was also studied at various radial and axial positions from the excitation source.

Early results indicate that with increasing excitation at the sound tip, higher energy dissipation rates are achieved near the surface of the ultrasonic probe. The flow behavior transitions from a turbulent to a laminar regime along the reactor. These dissipation rates help in determining reaction kinetics, which allow for future characterization and improved pharmaceutical development.