Catálogo de publicaciones - libros

One and two dimensional numerical simulations of the auto-ignition process of single droplets of methanol and n-heptane in air are presented. Detailed models are used to simulate the transport processes as well as the chemical kinetics. Efficient numerical methods are implemented to reduce the computing time.

The influence of different ambient parameters on the ignition process is investigated. The ambient gas temperature turns out to be the physical parameter with the largest influence on the ignition delay time. With increasing ambient temperature the ignition delay time decreases. Furthermore, the ignition delay time decreases with increasing pressure following a power law. Two dimensional simulations show the almost exponential dependence of the ignition delay time on the velocity of a gas counterfiow. If the counterfiow is too strong, the flame is extinguished. Furthermore, the location of ignition is strongly affected by the counterfiow velocity.

One and two dimensional numerical simulations of the auto-ignition process of single droplets of methanol and n-heptane in air are presented. Detailed models are used to simulate the transport processes as well as the chemical kinetics. Efficient numerical methods are implemented to reduce the computing time.

The influence of different ambient parameters on the ignition process is investigated. The ambient gas temperature turns out to be the physical parameter with the largest influence on the ignition delay time. With increasing ambient temperature the ignition delay time decreases. Furthermore, the ignition delay time decreases with increasing pressure following a power law. Two dimensional simulations show the almost exponential dependence of the ignition delay time on the velocity of a gas counterfiow. If the counterfiow is too strong, the flame is extinguished. Furthermore, the location of ignition is strongly affected by the counterfiow velocity.

Smoothed Particle Hydrodynamics (SPH) is a widely spread method in scientific computing. It is a grid-free method for particle simulations. Most of the existing implementations are written in FORTRAN and C and therefore difficult to maintain and to extend. Here we describe the design and the implementation of a parallel object-oriented framework for particle simulations written in C++. The key features of sph2000 are easy configurability, good extensibility and the constantly expanding range of applications. The use of design patterns lead to an efficient and clear design, simplifying further algorithmic and methodical modifications and extensions. Advances made in the field of hybrid parallelization improve the efficiency and the portability of parallel applications. In addition the implementation of parallel I/O enhanced the performance significantly. The method was also upgraded by concepts to permit the simulation of compressible problems with free surfaces like spray atomization and to consider surface tension in these simulations.

The results of research of industrial problems, such as, pipeline transport of oil and reforming in catalytic reactor are presented in the paper. The first part of the work is devoted to the calculation of hydrodynamics and heat exchange of a turbulent pipe flow of oil-mixture with additives. In the second part the mathematical model of reforming process and results of calculation of aerodynamics, heat and mass transfer in a catalytic reactor are presented.

Large-eddy simulations (LES) of two complex flow problems, a continuous tundish flow and the flow around multi-element airfoils are presented. The numerical computations are performed by solving the conservation equations for compressible fluids. An implicit dual time stepping scheme combined with low Mach number preconditioning and a multigrid accelerating technique is developed for LES computations. The method is validated by comparing data of turbulent pipe flow at =1280 and cylinder flow at Re=3900 at different Mach numbers with experimental findings from the literature. Finally, the characteristics of the flow in a one-strand tundish is analyzed and a solution for a flow around a two-element airfoil as well as a zonal solution for the trailing edge region are discussed.

Large-eddy simulations (LES) of two complex flow problems, a continuous tundish flow and the flow around multi-element airfoils are presented. The numerical computations are performed by solving the conservation equations for compressible fluids. An implicit dual time stepping scheme combined with low Mach number preconditioning and a multigrid accelerating technique is developed for LES computations. The method is validated by comparing data of turbulent pipe flow at =1280 and cylinder flow at Re=3900 at different Mach numbers with experimental findings from the literature. Finally, the characteristics of the flow in a one-strand tundish is analyzed and a solution for a flow around a two-element airfoil as well as a zonal solution for the trailing edge region are discussed.

The prediction of unsteady vortex dominated flows show is a challenging task, applying classical RANS simulations often fails and leads to poor results. Here a VLES approach is shown. For this approach an adaptive turbulence model based on the k- model of Kim and Chen is developed. Applying this approach to vortex dominated flows - vortex rope in a straight diffuser and tip vortex at a ship propeller - leads to an increase on computational accuracy. Therefore this approach seems to be suitable for this types of flows.