observed for predictions of productivity. Thus, these suggest that the kinetics
multi-scale model is suitable and precise to be utilized for yield and productivity
predictions within a certain range of aeration rate and stirrer speed. With the
implementation of the proposed kinetics multi-scale model into CFD simulations,
the non-ideally mixed mechanism of the bioreactor could be observed and could
enhance the physiology of the fermentation process.
A computational fluid dynamic simulation study has been performed by Krühne
et al. (2010), in which the interaction between the fluid dynamic conditions and the
growth of cells has been studied. A simple Michaelis–Menten type kinetic model
has been selected in which a shear stimulation factor was incorporated. With this
model it was possible to study the complex interaction between the cells and the
flow through a model pore. It could be confirmed that the growth of cells under
shear stimulation follow a different qualitative growth pattern than a non-shear
stimulated growth of cells. The cells again influence the distribution of the flow
through a pore and will result in a different local shear stress pattern.
The fluid flow inside and around a scaffold in a bioreactor is complex. Yan et al.
(2011) present an investigation into such a flow within scaffolds cultured in both
perfusion and non-fusion bioreactors, respectively. The simulation results demonstrate that the perfusion bioreactor provides a strong flow within the tissue
scaffold, thus increasing the shear stress on the scaffold surface compared to the
non-perfusion bioreactor. The results show that the value of the strand diameter
and horizontal span can affect the shear stress generated on the scaffold. The effect
of flow rate, a controllable parameter in the cell culture process, was also investigated and it was found that the average shear stress level increased linearly with
the flow rate. The knowledge obtained from this research provides a quantitative
insight into the velocity field and the shear stresses distribution within the scaffold
cultured in bioreactors. The effects of the controllable factors identified by this
study can be used to guide future scaffold design as well as experimental studies.
A co-current gas–liquid up-flow bubble column (10 cm ID and 1.88 m height)
has been simulated by Mahajan (2011) using Fluent. The various parameter
studied include bed dynamics such as phase holdups, pressure drop, velocity
profile, and gas–liquid mass transfer. The eulerian–eulerian approach with mixture
multiphase model and segregated solver was used. The standard k-e model has
been used to model turbulence. The species model was used to simulate the
oxygen transfer from gas to liquid as species in the two phases.
Microchannels have demonstrated to be potential to CFD application. Primarily, the study has been carried in order to know the behavior of spread of two
different viscous materials within each other through a microscopic needle. This
flow understanding is part of the global concept of the irrigation dripping tripled
perfusion bioreactor. One of the next steps after this current work is to integrate
many needles in parallel and analyze the bioreactor internal flow (David et al.
2012).
Liovic et al. (2012) present a CFD model that is shown to be a realistic model of
the hydrodynamics within a Corning stirrer-flask. The CFD models feature room
for improvement through targeted improvements to turbulence modeling, stirrer
358
G. De la Torre-Gea et al.
multi-scale model is suitable and precise to be utilized for yield and productivity
predictions within a certain range of aeration rate and stirrer speed. With the
implementation of the proposed kinetics multi-scale model into CFD simulations,
the non-ideally mixed mechanism of the bioreactor could be observed and could
enhance the physiology of the fermentation process.
A computational fluid dynamic simulation study has been performed by Krühne
et al. (2010), in which the interaction between the fluid dynamic conditions and the
growth of cells has been studied. A simple Michaelis–Menten type kinetic model
has been selected in which a shear stimulation factor was incorporated. With this
model it was possible to study the complex interaction between the cells and the
flow through a model pore. It could be confirmed that the growth of cells under
shear stimulation follow a different qualitative growth pattern than a non-shear
stimulated growth of cells. The cells again influence the distribution of the flow
through a pore and will result in a different local shear stress pattern.
The fluid flow inside and around a scaffold in a bioreactor is complex. Yan et al.
(2011) present an investigation into such a flow within scaffolds cultured in both
perfusion and non-fusion bioreactors, respectively. The simulation results demonstrate that the perfusion bioreactor provides a strong flow within the tissue
scaffold, thus increasing the shear stress on the scaffold surface compared to the
non-perfusion bioreactor. The results show that the value of the strand diameter
and horizontal span can affect the shear stress generated on the scaffold. The effect
of flow rate, a controllable parameter in the cell culture process, was also investigated and it was found that the average shear stress level increased linearly with
the flow rate. The knowledge obtained from this research provides a quantitative
insight into the velocity field and the shear stresses distribution within the scaffold
cultured in bioreactors. The effects of the controllable factors identified by this
study can be used to guide future scaffold design as well as experimental studies.
A co-current gas–liquid up-flow bubble column (10 cm ID and 1.88 m height)
has been simulated by Mahajan (2011) using Fluent. The various parameter
studied include bed dynamics such as phase holdups, pressure drop, velocity
profile, and gas–liquid mass transfer. The eulerian–eulerian approach with mixture
multiphase model and segregated solver was used. The standard k-e model has
been used to model turbulence. The species model was used to simulate the
oxygen transfer from gas to liquid as species in the two phases.
Microchannels have demonstrated to be potential to CFD application. Primarily, the study has been carried in order to know the behavior of spread of two
different viscous materials within each other through a microscopic needle. This
flow understanding is part of the global concept of the irrigation dripping tripled
perfusion bioreactor. One of the next steps after this current work is to integrate
many needles in parallel and analyze the bioreactor internal flow (David et al.
2012).
Liovic et al. (2012) present a CFD model that is shown to be a realistic model of
the hydrodynamics within a Corning stirrer-flask. The CFD models feature room
for improvement through targeted improvements to turbulence modeling, stirrer
358
G. De la Torre-Gea et al.