Granular materials and the associated processing processes are highly significant to the economy and, at the same time, they are an exciting area of research in the simulation of complex fluids. Approximately 60 % of the products in the chemical industry are granular materials – another 20 % of the products contain powdered forms. For efficient processing, the process behavior plays a key role, that is, the interaction between physical properties. From another perspective, it is precisely these physical properties that place high demands on flow modeling, as well as the numeric algorithms to solve the nonlinear PDEs.
In joint development projects with industry partners, it has been shown that besides the challenges already mentioned, the characterization of the granular materials is an essential component of predictive simulations. Last year we successfully completed the first ZIM project for single-phase characterization of granular materials. An MEF project in cooperation with Fraunhofer IKTS was initiated for two-phase characterization of granular air flows. In the framework of these projects as well as other ongoing projects to simulate air driven granular flows, bead mills, mixers, and silos, the available simulation solvers are being extended to include characterization into the simulation infrastructure. The mid-term goal is a simulation with the characterized materials of our industry partners.
This method is especially useful in the modeling of granular single-phase, multi-phase, and even suspension flows – a new area of modeling – because the characterizations must be performed with regard to the model being solved. In other words, only models with experimentally characterizable parameters are considered. Furthermore, new technologies were developed last year within GRAIN. In particular these involve the utilization of simulation for detailed spatial resolution problems as well as for investigating long-term flow patterns. As to the former, local grid refinement in granular flow solvers is now provided, which facilitates more detailed resolution, especially, for example, for the movable parts in mixers or bead mills. Concerning the analysis of long-term flow patterns, it is now possible to simulate, on the basis of previously existing detailed simulation, a time segment with quasi-stationary behavior with tracer particles for a statistically relevant long period. This is possible in fast processes (mixers) as well as for long term discharge experiments with silos.