Machine learning-based identification of precursors of extreme events in chaotic systems

Abrupt and rapid high-amplitude changes in a dynamical system’s states known as extreme events appear in many processes occurring in nature, such as drastic climate patterns, rogue waves, or avalanches. These events often entail catastrophic effects, therefore their description and prediction is of great importance. Nevertheless, because of...

Unraveling Flashback Phenomena of Turbulent premixed Hydrogen-Natural Gas-Air Flames

The growing energy demand and climate change poses a need for alternative energy generation in terms of renewable resources. Renewable energy resources are characterised by their intermittent behaviour. A backup power supply is required that can deliver electricity when the supply from the renewables is not sufficient. Gas turbines operating...

Drag Reduction in Turbulent Flows by Polymers and Surfactants: An Experimental Study Into the Mechanisms of Drag Reduction by Additives

In 1949, Toms (Toms B.A., (1949, 1977)) observed that small amounts of a drag reducing agent (DRA) could cause a considerable drag reduction in turbulent pipe flow. In application of polymer enhanced oil recovery, degradation of polymers in the supply lead could cause clogging. It was, however observed that surfactants at sufficiently high...

The shadow position mixing model tested for two turbulent flows

Predicting the behavior of turbulent flows and how thermochemical properties develop such as temperature, enthalpy or concentrations is an import aspect in various fields. However, numerical calculations have a high time complexity. Therefore, models were constructed to approximate these flows. This thesis focuses on using probability density...