Application of CFD to Analyze the Hydrodynamic Behaviour of a Bioreactor with a Double Impeller

Abstract

Stirred bioreactors are commonly used unit operations in the pharmaceutical industry. In this study, computational fluid dynamics (CFD) was used in order to analyze the influence of the impeller configuration (Segment–Segment and Segment–Rushton impeller configurations) and the impeller rotational speed (an operational parameter) on the hydrodynamic behaviour and mixing performance of a bioreactor equipped with a double impeller. A relatively close agreement between the power values obtained from the CFD model and those measured experimentally was observed. Various parameters such as velocity profiles, stress generated by impellers due to the turbulence and velocity gradient, flow number, and mixing time were used to compare the CFD simulations. It was observed that the impeller’s RPM could change the intensity of the interaction between the impellers when a Segment–Rushton impeller was used. In general, increasing the RPM led to an increase in total power and the stress acting on the cells and to a shorter mixing time. At a constant RPM, the Segment–Rushton impeller configuration had higher total power and stress acting on cells compared to the Segment–Segment impeller configuration. At lower RPM values (i.e., 50 and 100), the Segment–Segment impeller provided a shorter mixing time. Conversely, at the highest RPM (i.e., 150) the Segment–Rushton impeller had a shorter mixing time compared to the Segment–Segment impeller; this was attributed to the high level of turbulence generated with the former impeller configuration at high RPM.

A model‐driven approach towards rational microbial bioprocess optimization

“…Typically, high shear strain rates centered on the zone of the two impellers and alleviated with increasing distance from the impellers as exhibited in the contour plots. A high intensity of shear strain rate, which is proportional to the shear stress, within a stirred tank is often undesirable as it may result in cell morphology deformation and cause damage to the cells (Ebrahimi et al, 2019).…”

Cultivating Multidisciplinarity: Manufacturing and Sensing Challenges in Cultured Meat Production

“…Therefore, a lot of computational models are focused on the optimization of fluid behavior in bioreactors, while a lot of biological models are focused on the cell culturing process in the bioreactors. Hence, considering the complexity of a bioreactor system, and the importance of controlling and predicting systems’ behavior, different predictive computational models were proposed in the literature based on computational fluid dynamics (CFDs) [ 154 , 155 , 156 , 157 , 158 , 159 , 160 , 161 ].…”

“…In order to optimize the mixing process, recently proposed studies were examining an optimal impeller configuration for stirred tank BRs by using CFD [ 160 , 161 , 162 , 163 , 164 ]. The proposed geometries of impellers were based on Segment–Segment, Segment–Rushton [ 160 ], Scaba, Paddle [ 161 ], Elephant ear [ 162 ], blade turbines [ 163 ], and radial geometry of impellers [ 164 ]. The impeller shape has an important influence on cell cultivation due to the stress it causes.…”

Validation of Novel Lattice Boltzmann Large Eddy Simulations (LB LES) for Equipment Characterization in Biopharma

“…The power consumption can be calculated from the overall torque derived from the pressure and tangential stress distribution on steady and moving walls. The resulting power numbers were shown to be predicted accurately by the Reynolds-averaged Navier-Stokes (RANS) k − ε model, using the steady-state Multiple Reference Frame (MRF) approach to account for impeller rotation [16][17][18]. This computationally inexpensive method was proven to be a valuable tool for efficient equipment characterization to facilitate scale-up, as the simulation time was reported to be reduced by an order of magnitude, compared to other turbulence models [19,20].…”