Alexander Kuhn

Zuse-Institut Berlin | ZIB · Department of Visualization and Data Analysis

We demonstrate a technique to visualize multiple scales of atmospheric flow fields and the Lagrangian patterns therein, simulated by state-of-the-art simulation models for each scale. They provide insight into the structural differences and patterns that occur on each scale and highlight the complexity of flow phenomena in our atmosphere. For visua...

Many scientific applications deal with data from a multitude of different sources, e.g., measurements, imaging and simulations. Each source provides an additional perspective on the phenomenon of interest, but also comes with specific limitations, e.g. regarding accuracy, spatial and temporal availability. Effectively combining and analyzing such m...

To improve existing weather prediction and reanalysis capabilities, high-resolution and multi-modal climate data becomes increasingly important. High-resolution numerical simulation of atmospheric phenomena provides new means to understand dynamic processes and to visualize structural flow patterns. In the presented figures, we demonstrate an advan...

Large-eddy simulations (LES) with the new ICOsahedral Non-hydrostatic atmosphere model (ICON) covering Germany are evaluated for four days in spring 2013 using observational data from various sources. Reference simulations with the established Consortium for Small-scale Modelling (COSMO) numerical weather prediction model and further standard LES c...

Traditionally, Lagrangian fields such as finite-time Lyapunov exponents (FTLE) are precomputed on a discrete grid and are ray casted afterwards. This, however, introduces both grid discretization errors and sampling errors during ray marching. In this work, we apply a progressive, view-dependent Monte Carlo-based approach for the visualization of s...

In this poster, the properties of the newly introduced spectral proper orthogonal decomposition (SPOD) are demonstrated from a visualization point of view. The SPOD is a method to decompose time-resolved data from turbulent flows. It is based on classic proper orthogonal decomposition (POD) with an additional temporal constraint. The new method all...

We consider the spectral proper orthogonal decomposition (SPOD) for experimental data of a turbulent swirling jet. This newly introduced method combines the advantages of spectral methods, such as Fourier decomposition or dynamic mode decomposition, with the energy-ranked proper orthogonal decomposition (POD). This poster visualizes how the modal e...

Many scientific applications deal with data from a multitude of different sources, e.g., measurements, imaging and simulations. Each source provides an additional perspective on the phenomenon of interest, but also comes with specific limitations, e.g. regarding accuracy, spatial and temporal availability. Effectively combining and analyzing such m...

In the present study a flow simulation of a rotor hovering in ground effect was performed and compared to an experimental study from literature. Different reconstruction schemes in the finite volume flow solver were employed, leading to a computation of second and fifth order accuracy in space. The higher order computation was also performed on dif...

Understanding the hemodynamics of blood flow in vascular pathologies such as intracranial aneurysms is essential for both their diagnosis and treatment. Computational Fluid Dynamics (CFD) simulations of blood flow based on patient-individual data are performed to better understand aneurysm initiation and progression and more recently, for predictin...

Lagrangian coherent structures (LCSs) have become a widespread and powerful method to describe dynamic motion patterns in time-dependent flow fields. The standard way to extract LCS is to compute height ridges in the finite-time Lyapunov exponent field. In this work, we present an alternative method to approximate Lagrangian features for 2D unstead...

Recent research in flow visualization is focusing on the analysis of time-dependent, but mass-less particles. However, in many application scenarios, the mass of particles – and their resulting inertia – is essential in understanding fluid mechanics. This includes critical processes, such as dust particles interacting with aircraft (e.g., brown-or...

Trajectory visualization is an important tool to capture intrinsic characteristics of vector fields. However, often this class of geometric visualization suffers from visual clutter due to the number of curves that occlude each other and may cover relevant features. Attempts trying to avoid this effect often require complex pre/post-processing for...

The availability of dense motion information in computer vision domain allows for the effective application of Lagrangian techniques that have their origin in fluid flow analysis and dynamical systems theory. A well established technique that has been proven to be useful in image-based crowd analysis are Finite Time Lyapunov Exponents (FTLE). Based...

The extraction of motion patterns from image sequences based on the optical flow methodology is an important and timely topic among visual multi media applications. In this work we will present a novel framework that combines the optical flow methodology from image processing with methods developed for the Lagrangian analysis of time-dependent vect...

Human action recognition requires the description of complex motion patterns in image sequences. In general, these patterns span varying temporal scales. In this context, Lagrangian methods have proven to be valuable for crowd analysis tasks such as crowd segmentation. In this paper, we show that, besides their potential in describing large scale m...

In the 2011 IEEE Visualization Contest, the dataset represented a high-resolution simulation of a centrifugal pump operating below optimal speed. The goal was to find suitable visualization techniques to identify regions of rotating stall that impede the pump's effectiveness. The winning entry split analysis of the pump into three parts based on th...

The Finite Time Lyapunov Exponent (FTLE) has become a widespread tool for analyzing unsteady flow behavior. For its computation, several numerical methods have been introduced, which provide trade-offs between performance and accuracy. In order to decide which methods and parameter settings are suitable for a particular application, an evaluation o...

Vector fields are a common concept for the representation of many different kinds of flow phenomena in science and engineering. Methods based on vector field topology are known for their convenience for visualizing and analysing steady flows, but a counterpart for unsteady flows is still missing. However, a lot of good and relevant work aiming at s...

This paper proposes a vector field visualization approach that extracts and visualizes grouped regions of static 3D vector fields of similar curvature behavior. These regions are argued to ease the recognition of regions of potential interest and accelerate the general exploration process of vector fields. Our approach detects regions of similar ge...

This thesis deals with the topic of sketch-based 3D shape design as a special case of 3D modeling. Its purpose is to discuss, develop and implement a sketch-based modeling prototype, which is built upon experiences made with earlier systems. The focus thereby is on developing an intuitive, consistent and expressive modeling metaphor. This combines...

1 Zielsetzung und Problembeschreibung Diese Arbeit beschreibt eine visuelle Funktionsanalyse einer zentrifugalen Pumpe (Abb. 1) [1], für welche sowohl etablierte als auch neu entwickelte Visualisierungstechniken eingesetzt werden. Eine solche Pumpe besteht aus einem Einströmbereich, einem Transportbereich, in dem ein Impeller das Fluid beschleunigt...

In this work we are going to present our results analyzing a cen-trifugal pump as a part of the IEEE Visualization Contest 2011. The given data set represents a high resolution simulation of a cen-trifugal pump operating below optimal speed settings. Our goal is to find suitable visualization techniques to identify areas of re-circulation that impe...

Introduction: In this work we present our results for applying specially designed time-dependent flow visualization methods to a simulation of a centrifugal pump. The simulation has been performed on a high-resolution grid (Figure 1) for 80 time steps using three turbulence methods (SAS, DES, SST [1]) with special focus on the analysis of the so ca...