Our Research Dimensions

Prof. Dr.-Ing. Christian Hasse,
Head of STFS

Simulation has become the third scientific pillar, alongside theory and experiment.

Christian Hasse

Our Research Dimensions at STFS

Our research at the STFS can be arranged in four dimensions:

  • Configurations
  • Energy Carriers
  • Theory and Physical Modeling
  • Computational Methods

These are presented in more detail.

Configurations

We investigate configurations ranging from simple laminar, freely propagating flames to complex technical combustion chambers. As part of this, we examine laboratory flames which are designed for the targeted analysis of physical effects during combustion. Thus, we bridge the gap between basic research and application.

Energy Carriers

The energy carriers we investigate range from gaseous hydrogen to iron and aluminum powder, all of which come with their own challenges.

Theory and Physical Modeling

At the STFS we conduct research into flamelet theory, apply large-eddy simulations (LES) and develop corresponding models, for example models for artificial flame thickening for turbulence-chemistry interaction.

Computational Methods

Computational methods are essential for our research in order to be able to examine our models in different configurations under consideration of the various fuels. The focus here is on high-performance computing on state-of-the-art supercomputers and the subsequent analysis and visualization of the simulation results.

Research Areas at STFS

Our research dimensions are integrated into various research areas, which also form the basis of our internal organizational structure. However, the areas do not form sharp boundaries, but overlap in many aspects and blend into one another. For example, the models developed in fundamental research on laminar and turbulent flames are also used in simulations of aircraft engines and the software we use for the simulation of multiphase and multicomponent flows is identical.

Software

At STFS, we use various software tools to develop, validate and apply models. These are primarily simulation software packages for numerical flow simulations, which offer options for simulating multiphase and multicomponent reactive flows. Our in-house developed software ULF (Universal Laminar Flame Solver) is mainly used in model development and model validation for the numerical solution of 0D, 1D and 2D problems (e.g. for the solution of flamelet equations and balance equations of generic flame configurations). We use the newly developed GPU-accelerated spectral element Navier-Stokes solver nekRS as the basis for model development by means of direct numerical simulations (DNS) of turbulent reactive flows.

The most widely used software at STFS is the open source program OpenFOAM®. It is used for laminar direct numerical simulations in model development and model validation, as well as for coupling our models with scale-resolving coarse-structure simulations.

We also use commercial CFD software in cooperation with industrial partners and for certain technical applications.

Extensive computing capacities are available with the infrastructure of NHR4CES, which includes the Lichtenberg high-performance computer of TU Darmstadt and the CLAIX high-performance computer of RWTH Aachen University.

We also operate our own computing cluster for smaller-scale simulations.

Simulation techniques are a platform on which scientific theories can be applied and investigated by solving mathematical models numerically. By comparing simulative and experimental data, the quality of these mathematical models can be assessed. This process includes model development and implementation, the application of the numerical framework and the analysis and interpretation of the numerical results. In a position paper by the German Science Council, simulation is emphasized as a strategically important field of science and it is proposed to train a sufficient number of young scientists at universities with a focus on simulations. It also encourages the intensification of cooperation between the various scientific disciplines and industry. As a result, it can be stated that simulation is now established as the third pillar of science alongside theory and experiment.

In our research, we apply simulation methods with a focus on reactive thermo-fluid systems. This includes, in particular, processes that take place during the combustion of chemical energy carriers such as hydrogen and ammonia, but also of metal powder such as iron and aluminum. Such highly complex processes take place on many scales, all of which need to be considered and understood in order to build up a scientific understanding, develop models and ultimately optimize the processes.

On the one hand, ignition behavior, pollutant formation and the combustion of individual solid fuel particles must be investigated, understood and modeled in homogeneous reactors and one-dimensional laminar flame configurations.

We also use generic flame configurations to develop flamelet models that can be used to significantly reduce the number of equations to be solved in simulations, which offers great potential for accelerating simulations.

On the other hand, direct numerical simulations (DNS) of three-dimensional turbulent flame configurations contribute to a general understanding of turbulent combustion and, in addition to experimental data, serve for the validation and derivation of models, for example for the turbulence-chemistry interaction (TCI). The developed models are then mainly used in scale-resolving large-eddy simulations (LES). This allows us to simulate and analyze in detail not only generic flame configurations and laboratory flame configurations developed to advance the fundamental scientific understanding of turbulent combustion, but also practical applications such as aircraft engines, industrial furnaces and chemical reactors.