@phdthesis{Hupp2008, author = {Hupp, Markus}, title = {Simulating Star Formation and Turbulence in Models of Isolated Disk Galaxies}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-34510}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2008}, abstract = {We model Milky Way like isolated disk galaxies in high resolution three-dimensional hydrodynamical simulations with the adaptive mesh refinement code Enzo. The model galaxies include a dark matter halo and a disk of gas and stars. We use a simple implementation of sink particles to measure and follow collapsing gas, and simulate star formation as well as stellar feedback in some cases. We investigate two largely different realizations of star formation. Firstly, we follow the classical approach to transform cold, dense gas into stars with an fixed efficiency. These kind of simulations are known to suffer from an overestimation of star formation and we observe this behavior as well. Secondly, we use our newly developed FEARLESS approach to combine hydrodynamical simulations with a semi-analytic modeling of unresolved turbulence and use this technique to dynamically determine the star formation rate. The subgrid-scale turbulence regulated star formation simulations point towards largely smaller star formation efficiencies and henceforth more realistic overall star formation rates. More work is necessary to extend this method to account for the observed highly supersonic turbulence in molecular clouds and ultimately use the turbulence regulated algorithm to simulate observed star formation relations.}, subject = {Astrophysik}, language = {en} } @phdthesis{Maier2008, author = {Maier, Andreas}, title = {Adaptively Refined Large-Eddy Simulations of Galaxy Clusters}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-32274}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2008}, abstract = {It is aim of this work to develop, implement, and apply a new numerical scheme for modeling turbulent, multiphase astrophysical flows such as galaxy cluster cores and star forming regions. The method combines the capabilities of adaptive mesh refinement (AMR) and large-eddy simulations (LES) to capture localized features and to represent unresolved turbulence, respectively; it will be referred to as Fluid mEchanics with Adaptively Refined Large-Eddy SimulationS or FEARLESS.}, subject = {Turbulenz}, language = {en} } @phdthesis{Paul2010, author = {Paul, Surajit}, title = {Evolution of shocks and turbulence in major galaxy-cluster mergers}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-47266}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2010}, abstract = {Mergers between rich clusters of galaxies represent the most violent events in the Universe. The merger events initiate a complex chain of processes that leads to the dissipation of the collisional energy. This phase of violent relaxation is accompanied by turbulence and shock waves as well as non-thermal particle acceleration. This thesis aims at the interpretation of multi-wavelength observations of the merging cluster of galaxies Abell 3376 in the framework of a theoretical model of the involved effects. Observations with the Very Large Array radio interferometer were carried out and analyzed to clarify the morphology of the non-thermal particle distribution in Abell 3376, in particular about the shocked regions. The dissipation in the hot intra-cluster gas was studied using archival X-ray observations with ROSAT and XMM. Results were compared with constrained numerical simulations of the evolution of the merger process in the framework of cosmological structure formation. For this purpose, the ENZO-Code was employed for the computation of the gas dynamics and self-gravity of the colliding mass distribution. The non-thermal properties of the intra-cluster gas could be indirectly inferred from the local Mach number and the strength of the turbulence.}, subject = {Galaxienhaufen}, language = {en} }