Academic Papers

Predicting the diameters of droplets produced in turbulent liquid–liquid dispersion
AiCHE Journal (February 2022)
John A. Thomas, Brian DeVincentis, Johannes Wutz, Francesco Ricci

The droplet size distribution in liquid–liquid dispersions is a complex convolution of impeller speed, impeller type, fluid properties, and flow conditions. In this work, we present three a priori modeling approaches for predicting the droplet diameter distributions as a function of system operating conditions. 

Modeling Mass Transfer in Stirred Microbioreactors
Chemical Engineering Science (2022)
Hooman Farsani, Johannes Wutz, Brian DeVincentis, John A Thomas, Seyed Pouria Motevalian

Microbioreactors play a pivotal role in making biologic medicines. In fact, 10 of the top 15 selling drugs worldwide were made in a bioreactor. In this paper, M-Star and Pfizer present a generalized framework for modeling mass transfer in two-stage, stirred tank bioreactors to aid the scale-up process.

Validation of Novel Lattice Boltzmann Large Eddy Simulations (LB LES) for Equipment Characterization in Biopharma
Processes (2021)
Maike Kuschel, Jürgen Fitschen, Marko Hoffmann, Alexandra von Kameke, Michael Schlüter, Thomas Wucherpfennig

In this study, transient LB LES were applied to simulate a 3 L bioreactor system. The results were compared to novel 4D particle tracking (4D PTV) experiments, which resolve the motion of thousands of passive tracer particles on their journey through the bioreactor.

A CFD Digital Twin to Understand Miscible Fluid Blending
AAPS PharmSciTech (2021)
John Thomas, Kushal Sinha, Gayathri Shivkumar, Lei Cao, Marina Funck, Sherwin Shang, Nandkishor K. Nere

The mixing of stratified miscible fluids with widely different material properties is a common step in biopharmaceutical manufacturing processes. Differences between the fluid densities and viscosities, however, can lead to order-of-magnitude increase in blend times relative to the blending of single-fluid systems.

A Mechanistic Approach for Predicting Mass Transfer in Bioreactors
Chemical Engineering Science (2021)
John A. Thomas, Xiaoming Liu, Brian DeVincentis, Helen Hua, Grace Yao, Michael C. Borys, Kathryn Aron, Girish Pendse

In this work, we propose, implement, and validate a mechanistic transport model for predicting oxygen transfer rates within stirred tank bioreactors. To begin, we describe the relevant conservation laws and key principles from turbulence theory that govern mass transfer.

Novel Evaluation Method to Determine the Local Mixing Time Distribution in Stirred Tank Reactors
Chemical Engineering Science: X (2021)
J. Fitschen, S. Hofmann, J. Wutz, A.v. Kameke, M. Hoffmann, T. Wucherpfennig, M. Schlüter

A novel image analysis will be presented in this study for the detailed characterization of mixing processes by taking into account the history of mixing. The method is based on the experimental determination of the local mixing time distribution by using a multi-color change caused by a pH-change in a bromothymol blue solution.

Time Scales and Turbulent Spectra above the Base of Stirred Vessels from Large Eddy Simulations
Flow, Turbulence and Combustion (2020)
Jason J. Giacomelli, Harry E. A. Van den Akker

Single-phase Large Eddy Simulations (LESs) have been conducted with M-Star CFD software to compute spectra and time scales of the turbulent flow field at positions above the base of a stirred tank as these time scales may be important to the application of solids suspension.

A Spectral Approach of Suspending Solid Particles in a Turbulent Stirred Vessel
Transport Phenomena and Fluid Mechanics (2020)
Jason J. Giacomelli, Harry E. A. Van den Akker

The 2015 Grenville-Mak-Brown (GMB) correlation for predicting the just suspended condition assumes that the length scale of the suspending eddy is equivalent to the particle diameter. This article investigates the role of the time scale of the relevant eddies with respect to the particle response time.