The Computational Fluid Dynamics (CFD) group is concerned with the application and development of CFD-based methods for the description of technically relevant process engineering processes. These are often characterized by a strong coupling of transport phenomena on different spatial and temporal scales. Therefore, an efficient rigorous CFD-based description of these systems is often not possible.

The focus of the working group is therefore the development of efficient methods for the description and optimization of industry-relevant processes by:

1.     Coupling CFD with specialized external tools, e.g. for the calculation of reaction kinetics or simplified reactor modeling.
2.     The development of coarse-graining approaches for CFD-DEM simulations.
3.     The combination of CFD and classical process modeling tools. Here, CFD is used to determine the effective transport parameters required for process modeling.
4.     The development of efficient meshing strategies.

On the application side, the focus is on the one hand on the spatially resolved simulation of catalytic fixed-bed reactors. Here, concepts for intensifying the radial heat transport, e.g. by varying the particle shape or by placing internals in the reactor tube, are investigated on a mesoscopic scale. Furthermore, effective transport parameters can be determined based on the CFD simulations, which can subsequently be used at the process simulation level. On the other hand, turbulent closure conditions are further developed by high-resolution DNS simulations.

A second application focus is the simulation of fluidized particulate systems based on the Discrete Element Method (DEM). DEM is currently not applicable for industrial scale simulations due to the very high computational requirements. Therefore, different coarse-graining approaches are fundamentally investigated and extended. The goal is to be able to reliably describe fluid dynamics and transport processes in large-scale plants by means of coarse-grained DEM.

The CFD-based optimization of stirred systems represents a third main topic. In particular, the determination of the mixing time is associated with a high numerical effort due to the necessary time-resolved simulations. This has to be reduced in order to perform optimization studies efficiently. By using the Mean Age Theory it is in principle possible to transfer the determination of the mixing time into a stationary problem. The extent to which this leads to valid results is the focus of our work.

The development of a CFD-based "digital image" for SCR systems (Selective Catalytic Reduction) is another application focus. In order to comply with the very strict emission regulations that will apply from 2023 under the 44th BImSchV (Federal Immission Control Ordinance), very clean SCR systems must be developed. These are necessary in order to be able to use clean and CO2-neutral biomass in combined heat and power plants (CHP) in the future. Based on a Lagrangian simulation framework, methods are developed to describe spray dispersion, droplet evaporation, possible wall interactions (possibly with film formation) and transport processes in the gas phase.