CFD modelling of a wave-mixed bioreactor with complex geometry and two degrees of freedom motion

Abstract

Optimizing bioprocesses requires an in-depth understanding, from a bioengineering perspective, of the cultivation systems used. A bioengineering characterization is typically performed via experimental or numerical methods, which are particularly well-established for stirred bioreactors. For unstirred, non-rigid systems such as wave-mixed bioreactors, numerical methods prove to be problematic, as often only simplified geometries and motions can be assumed. In this work, a general approach for the numerical characterization of non-stirred cultivation systems is demonstrated using the CELL-tainer bioreactor with two degree of freedom motion as an example. In a first step, the motion is recorded via motion capturing, and a 3D model of the culture bag geometry is generated via 3D-scanning. Subsequently, the bioreactor is characterized with respect to mixing time, and oxygen transfer rate, as well as specific power input and temporal Kolmogorov length scale distribution. The results demonstrate that the CELL-tainer with two degrees of freedom outperforms classic wave-mixed bioreactors in terms of oxygen transport. In addition, it was shown that in the cell culture version of the CELL-tainer, the critical Kolmogorov length is not surpassed in any simulation.

Computational Fluid Dynamics for Advanced Characterisation of Bioreactors Used in the Biopharmaceutical Industry – Part II: Case Studies

“…is fixed, small folds may also form, neither of which were taken into account in the simulation [20].…”

Computational Fluid Dynamics for Advanced Characterisation of Bioreactors Used in the Biopharmaceutical Industry – Part I: Literature Review

“…There are also two different methods for orbitally shaken and wave-mixed bioreactors, both of which use a transient approach. The computational mesh can be manipulated by rotation and/or translation to mimic motion [44]. A less common method is to manipulate only the direction of the forces acting within the bioreactor.…”

“…( 10)). If this is determined for each mesh cell, a Kolmogorov length distribution in the bioreactor can be determined [44].…”

“…specific power input or mixing time) using meshes of different resolutions. A detailed description of this procedure is described in Ramírez et al [74] and Seidel et al [44]. Alternatively, methods like the grid systematic refinement or the curve fitting method can also be used [75].…”

Laboratory-independent exploration of stirred bioreactors and their fluid dynamics

“…If more complex geometries need to be visualized, 3D scanners can also be used to create the 3D geometry. For example, Zhan et al (2019) and Seidel et al (2022) scanned wave-mixed bioreactors to perform CFD simulations. The individual bioreactor components were then combined into an assembly drawing and exported as an .OBJ format.…”