Andreas Gerndt

VIRACOCHA: An Efficient Parallelization Framework for Large-Scale CFD Post-Processing in Virtual Environments

One recommended strategy for the analysis of CFD-data is the interactive exploration within virtual environments. Common visualization systems are unable to process large data sets while carrying out real-time interaction and visualization at the same time. The obvious idea is to decouple flow feature extraction from visualization. This paper covers the functionality of the parallel CFD post-processing toolkit Viracocha. Two aspects are discussed in more detail. The first approach covers strategies to reduce the loading time. Data caching and prefetching are employed to reduce access time. The second aspect concerns an approach called streaming that minimizes the time a user has to wait for first results. Viracocha already sends coarse intermediate data back to the virtual environment before the final result is available. Different streaming and data handling strategies are described. In order to emphasize the benefit of our implementation efforts, some strategies are applied to multi-block CFD data sets.

ViSTA FlowLib - framework for interactive visualization and exploration of unsteady flows in virtual environments

In the past a lot of work has been invested in various aspects of an interactive visualization of CFD simulation data. This includes e.g. increasing the rendering speed and responsiveness of complex visualizations, using and enhancing multimodal user interfaces, and incorporating parallel approaches for an ef cient extraction of ow properties and their respective visual representation. Still, only few projects combine the signi cant advances in these areas. In this paper, we describe our software framework ViSTA FlowLib, which facilitates merging current research results of various related areas. This is done by connecting dedicated sub-modules with clearly defined responsibilities through appropriate interfaces, whilst implementing sensible default behavior. ViSTA FlowLib combines efficient rendering techniques and a parallel computation of the visualization with intuitive multimodal user interfaces to allow for an interactive exploration of unsteady fluid flows in a virtual environment. Special care has been taken to achieve a high scalability in respect to computing power, projection technology, and input-output device availability.

Open source software framework for applications in aeronautics and space

The DLR developed the open source software framework RCE to support the collaborative and distributed work in the shipyard industry. From a technology side of view a software from the shipbuilding field has many requirements in common with aerospace software projects. Accordingly, RCE has become the basis for further projects within the DLR. Over the last years of usage a subset of frequently used software components could be derived and are provided by the RCE framework. In particular, the workflow engine, allowing the integration of different domain-specific tools from local and remote locations into one overall calculation has become important for various projects. We present RCE and show how its software components are reused in two aerospace applications.

An Evaluation of Open Source Physics Engines for Use in Virtual Reality Assembly Simulations

We present a comparison of five freely available physics engines with specific focus on robotic assembly simulation in virtual reality (VR) environments. The aim was to evaluate the engines with generic settings and minimum parameter tweaking. Our benchmarks consider the minimum collision detection time for a large number of objects, restitution characteristics, as well as constraint reliability and body inter-penetration. A further benchmark tests the simulation of a screw and nut mechanism made of rigid-bodies only, without any analytic approximation. Our results show large deviations across the tested engines and reveal benefits and disadvantages that help in selecting the appropriate physics engine for assembly simulations in VR.

Spherical Terrain Rendering using the hierarchical HEALPix grid

We present an interactive spherical terrain rendering system employing a hierarchical subdivision of the HEALPix coordinate system using quadtrees. Compared to other parameterizations, the scheme avoids singularities and allows for efficient fusion of mixed-resolution digital elevation models and imagery. A Level-of-Detail heuristic is used to guarantee both high performance and visual fidelity. Unified treatment of DEM and imagery data is achieved by performing the HEALPix projection within a GPU shader. The system is applied to the exploration of Mars, using both MOLA (NASA) and HRSC (German Aerospace Center) data sets.

OBC-NG: Towards a reconfigurable on-board computing architecture for spacecraft

The computational demands on spacecraft are rapidly increasing. Current on-board computing components and architectures cannot keep up with the growing requirements. Only a small selection of space-qualified processors and FPGAs are available and current architectures stick with the inflexible cold-redundant structure. The objective of the ongoing project OBC-NG (On-board Computer - Next Generation) is to find new concepts for on-board-computer to fulfill future requirements. The concept presented in this paper is based on a distributed reconfigurable system, consisting of different nodes for processing, management and interface operations. OBC-NG will exploit the high performance of commercial off-the-shelf (COTS) hardware parts. To compensate the shortcomings of COTS parts the OBC-NG redundancy approach differs from the classic way and error mitigation techniques will work mainly on software level. This paper discusses the hardware and software architecture of the system as well as the redundancy and reconfiguration concept. Our ideas will be proven in an OBC-NG prototype, planned for the next year.

Decision Support Tool for Concurrent Engineering in Space Mission Design

The concurrent engineering (CE) approach has been successfully applied to the early design phase of space missions. During CE sessions, a software support is needed to allow multidisciplinary design data exchange. At the moment, a spreadsheet-based solution enhanced with macros is used at the German Aerospace Center (DLR) to create a system model of a space mission during the early design phase. Now there is an increasing demand to take advantage of this system model and provide data analysis features which improve the decision making during CE sessions. Since the current approach is limited for such analysis, DLR has started developing a new tool called Virtual Satellite. It offers extended software support required by the Concurrent Engineering Facility of DLR in Bremen. On top of the previous spreadsheet functionalities, it provides means for online data analysis and system modeling. The results of these data analyses are presented to the discipline experts using different views which help in performing an early design optimization. In this paper, the impact of these views on the decision making during the AEGIS space mission study is presented as a proof of concept.

Nested OpenMP for efficient computation of 3D critical points in multi-block CFD datasets

Extraction of complex data structures like vector field topologies in large-scale, unsteady flow field datasets for the interactive exploration in virtual environments cannot be carried out without parallelization strategies. We present an approach based on Nested OpenMP to find critical points, which are the essential parts of velocity field topologies. We evaluate our parallelization scheme on several multi-block datasets, and present the results for various thread counts and loop schedules on all parallelization levels. Our experience suggests that upcoming massively multi-threaded processor architectures can be very advantageously for large-scale feature extractions

A Modular Architecture for an Interactive Real-Time Simulation and Training Environment for Satellite On-Orbit Servicing

This paper outlines the development of a real-time interactive application for the analysis, training and programming of on-orbit servicing tasks within a virtual reality environment. The main challenges put on the system are the real-time simulation of the realistic dynamic and kinematic behavior of satellite components and additionally integrate interaction through a bimanual haptic interface, as well as enable tele-operation of a robot. We give an overview of the application, describe the real-time challenges and outline our approach and proposed system structure.

Airflow simulation inside a model of the human nasal cavity in a virtual reality based rhinological operation planning system

Abstract The success rate of rhinological surgery is expected to be improved by changes of the nasal cavity geometry based on the assessment of the airflow via numerical simulation. Therefore, we are developing an operation planning system that combines Computational Fluid Dynamics (CFD) and Virtual Reality (VR) technology. In this paper, we introduce the systems design and a typical application. Results of a numerical simulation of the flow field in a model of the human nasal cavity are presented and compared with experimental data. The comparison shows a good agreement with the experimental findings.