Dr.-Ing. Stephan Lenz
Gas-Kinetic schemes for thermal compressible flows
Thermal compressible flows are characterized by large density ratios at low Mach numbers. Such flows are present in the case of fire. The heat released by the fire expands the fluid and leads hence to strong natural convection.
In civil engineering thermal compressible flows related to building fires are of great interest. The load capacity of concrete is reduced by chemical and mechanical processes. This can ultimately yield the collapse of the building and thus endanger the live of humans. A detailed prediction of the load capacity over time of the fire during the design phase is mandatory. Experiments are expansive, time-consuming and often not possible for the real system. Numerical computations can support the prediction of the load capacity during the design phase. Flow simulations in particular can produce boundary conditions for the structural analysis.
As numerical method for the flow simulation a high performance Gas-Kinetic scheme (GKS) is developed. GKS are explicit finite volume methods, where the fluxed derived from kinetic theory. In the past GKS was used in different aerodynamic applications. Further, we recently investigated a GKS for thermal air flow at large temperature ratios. In this project the GKS will be further improved for massive parallel hardware. For turbulence modeling variants of the large eddy simulation (LES) will be used. These require fine spatio-temporal discretization. The explicit nature of kinetic methods and their data locality encourage highly efficient massive parallelization on many-core architectures such as general purpose graphics processing units (GPGPUs). Further, combustion and radiation models will implemented to model heat sources and heat transfer.
Finally, simulated boundary conditions will be exchanged iteratively with the Institut für Statik to obtain a coupled solution for the load capacity over time during a fire.
Publications within the framework of the RTG:
Publications in peer-reviewed scientific journals:
S. Lenz, M. Geier and M. Krafczyk. An explicit gas kinetic scheme algorithm on non-uniform Cartesian meshes for GPGPU architectures. Computers & Fluids 186 (2019) 58-73.[ DOI ]
S. Lenz, M. Schönherr, M. Geier, M. Krafczyk, A. Pasquali, A. Christen and M. Giometto. Towards real-time simulation of turbulent air flow over a resolved urban canopy using the cumulant lattice Boltzmann method on a GPGPU. Journal of Wind Engineering and Industrial Aerodynamics 189 (2019) 151-162.[ DOI ]
S. Lenz, M. Krafczyk, M. Geier, S. Chen and Z. Guo. Validation of a two-dimensional gas-kinetic scheme for compressible natural convection on structured and unstructured meshes. International Journal of Thermal Sciences 136 (2019) 299-315.[ DOI ]
Conference contribution without publication in conference proceedings:
S. Lenz, M. Geier, M. Krafczyk, T. Stein, D. Dinkler. A coupled simulation approach for fire driven thermal compressible flows and thermal degeneration of concrete. Coupled 2019. Sitges, Spain. June 3-5, 2019.
S. Lenz, M. Geier and M. Krafczyk. GPGPU-Implementation of a Gas-Kinetic Scheme on Quadtree-type Cartesian meshes. ICMMES 2018. Newark, Delaware, USA. July 9-13, 2018.
S. Lenz, M. Krafczyk, M. Geier. Simulation of compressible natural convection with a gas-kinetic scheme in two dimensions. ICMMES 2017. Nantes, France. July 17-21, 2017.