Chemically reactive flows, computational fluid

One-dimensional reactive flow. As a preliminary trial problem in our computations of reactive flow, we have studied a simple situation in which a fluid obeying first-order chemical kinetics moves at constant velocity and temperature in the positive x direction. Here only the mass-transport equation is operative, and it takes the simple form ... 

Chemical reactions may also affect turbulence by releasing energy and modifying the fluid properties locally. The influence can be quite significant in variable density flows (e.g. combustion). Nevertheless, in many computational models of constant density reactive flow processes, it is implicitly assumed that chemical reactions do not affect scalar mixing rates. 

P. O Rourke, The KIVA computer program for multidimensional chemically reactive fluid flows with fuel sprays. Lecture Notes in Physics 241 (1985) 74. 

In a reactive flow with heat release, the dynamics of the fluid motion is coupled with the chemical reaction through the nonhomogeneous distribution due to the thermal expansion. Such a dynamic process must be solved by an appropriate formulation. FuUy compressible flow descriptions are the ones where density and pressure vary. They are more appropriate for flame-acoustic interactions and combustion in high-speed flows, but their computational costs are high at low-speed flow [13]. 

The current progress of CFD enables computational experiments in a reactor apparatus to reveal the RTD. Typically, CFD is used for nonreactive fluid systems, but nowadays reactive systems can also be computed as discussed in Ref [8]. The difficulties of CFD, however, increase considerably as multiphase systems with chemical reactions are examined. For this reason, a logical approach is to utilize CFD to catch the essential features of the flow pattern and to use this information in classical reactor models based on RTDs. 

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