Institute of Aerodynamics and Gas Dynamics
Tel.: +49 (0)711 685-63413
- Project A2 (“Development of numerical methods for the simulation of compressible droplet dynamic processes at extreme ambient conditions”) within collaborative research council SFB-TRR75
- Discontinuous Galerkin (DG) methods for compressible multi-phase flows at extreme ambient conditions
- Multicomponent flows
- Thermodynamic description of mixtures
- Direct numerical simulation
In many technical applications where multi-phase problems occur, operating pressures and temperatures obtain values close to the critical point of the fluid. These conditions can be found in injection systems of modern diesel or rocket engines. While the physical effects are not completely understood, it is known that in this regime compressibility effects and even shock waves in both, the liquid and the gaseous phases, cannot be neglected. Consequently, traditional solution approaches using incompressible flow solvers fail.
The significant difference of compressible flows is that the hydrodynamics and the thermodynamics of the fluid are coupled such that the pressure is linked to the inner energy by an equation of state. Close to the critical point, and especially when phase transition occurs, the physical phenomena present require sophisticated descriptions. Furthermore, realistic conditions consider multiple components, e.g. a single component droplet evaporating in an ambient gas environment. In the regime considered, thermodynamic properties of the mixture, such as the critical temperature and critical pressure, change significantly compared to the pure fluids.
Our solution procedure for compressible two-phase flows is based on three main components: the first is an approach to describe the position and the geometry of the phase interface and its temporal evolution using a level-set tracking algorithm. The second is a numerical method to treat the discontinuous nature of the interface as well as the related physics. Here we rely on the discontinuous Galerkin spectral element method where the phase interface is resolved sharply as a generalized Riemann problem. The third component is an accurate equation of state, suitable to describe the dissimilar behaviour of multi-phase flows.