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Beschreibung:
This thesis presents new techniques to the field of Flow Visualization that are based on the flow map. Water flowing down a river, the aerodynamics of a car, the air we breathe – flows, i.e., liquids or gases in motion, play an essential role in our everyday life. Understanding flows is essential in various fields. Therefore, they are of substantial research interest. The discipline of Flow Visualization aims for a meaningful visualization of information contained in flows. The techniques we can apply heavily depend on how the data is represented. One way that has gained research interest in the last years is the flow map. Flow maps are Lagrangian flow representations, i.e., they describe the movement of massless particles in the flow. They have particular properties that make them complex data structures. This thesis shows different ways to work with flow maps that can be classified into two parts. In the first part of this thesis, we consider the flow map structure and directly address its data. Based on a sound introduction, we develop a concept to modify flow maps. Each modification happens in a local area defined in space-time and entails a global adaption of different flow map parts. We present efficient techniques that handle this process while maintaining inherent flow map properties. Furthermore, we present drift fields, a novel technique to present flow data from the Lagrangian perspective. Drift fields implement advantages of flow maps but are easier to handle. We show their relation to flow maps and how to compute them. The second part of this thesis is related to flow features that we derive from the flow map. The extraction of ridge structures from finite-time Lyapunov exponent fields is a widely used approach for the computation of Lagrangian coherent structures. We present an approach that uses intermediate time steps and extracts highly resolved ridge geometries. Furthermore, we consider the phenomenon of recirculation in unsteady 3D flows. We show that particles with recirculating behavior form ...