ABSTRACT
Conservative Scalars ......................................................................... 133 6.4.2 The Issue of Turbulence Modeling in Single-Phase Bioreactors ...... 136 6.4.3 Specic Issues of Multiphase-Flow Bioreactors ............................... 137
6.5 Fundamentals of CFD Solver for Bioreactors: The Numerical Issue ........... 143 6.5.1 Discretization Methodology ............................................................. 143 6.5.2 Numerical Strategies......................................................................... 144
6.6 Application to Bioreactors through the Example of Bubble Columns ......... 148 6.6.1 Generalities ....................................................................................... 148 6.6.2 Preliminary Analysis of Bubble Column Bioreactors ...................... 149 6.6.3 Physical Modeling ............................................................................ 151 6.6.4 Numerical Strategy ........................................................................... 156 6.6.5 Beyond Hydrodynamics.................................................................... 159
6.7 Conclusions ................................................................................................... 160 References .............................................................................................................. 161
Computational uid dynamics (CFD) is usually dened as a set of numerical modeling tools able to simulate and predict the behavior of uid ows. CFD is also described as one of the three dimensions of uid mechanics, complementary to analytical methods and experimental techniques (Anderson 1995). It corresponds to the most recent of these elds, as CFD appeared in the 1960s, mainly for aeronautic applications. CFD corresponds, therefore, to a transdisciplinary eld between uid mechanics and applied mathematics. As a result, the development of CFD is closely linked to that of computers as ow predictions are always highly intensive in terms of CPU space and memory usage. A brief history of CFD is presented in Figure 6.1, but it must be kept in mind that CFD is still a rapidly evolving area of research, not only in terms of ow modeling, but also in terms of the fastest solution algorithms and simulation strategies.
