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Aerospace Application

In aerospace engineering and related fields safety-critical systems are developed. Simulations in every stage of the product development cycle are becoming more and more complex. For example, multidisciplinary coupled simulations or optimizations are being conducted in distributed computing environments. In order to get some level of confidence in the quality of the simulation results, it is important to record the complete history of the computation.

Computer based simulation is used extensively in many scientific and technical applications, for instance in the development and design of aircrafts and motor vehicles, or in forecasting the weather. In recent years, parallel computing has been very successful in reducing the computing time required for such modeling to acceptable levels. Nevertheless, the lack of interoperability and transparency of the tools used in parallel and distributed simulation systems still causes problems. With more complex and multi-disciplinary problems, users tend to spend much of their time configuring and connecting the tools needed for one particular simulation than running the simulation itself. The fields of development are diverging between the "traditional" HPC programming paradigm (using Message Passing) and the success and effort made with distributed object computing. In addition to the focus on pure parallel performance of a simulation, an environment for the process to run in is needed. TENT is an environment to overcome these problems and close the gap.

The Simulation Integration Environment TENT

TENT is a software integration and workflow management system that simplifies work by means of simulation process chains in distributed environments. In TENT all tools of a simulation can be integrated and centrally started and controlled from a user's desktop via a graphical user interface (GUI).

The major characteristics of TENT are:

  • Use of distributed computing resources (PCs, workstations, clusters or supercomputers with scheduling systems, and Computational Grids)

  • Visual presentation of workflows in a graphical user interface (GUI) available on all systems

  • Flexibility in setup, configuration, online control and online visualization of simulations

  • Integration of project-based data management including the option of collaborative work

  • Monitoring and control of an ongoing simulation from any computer

  • Simple integration of existing applications

  • Automatic, high-performance data exchange between all the steps of a distributed simulation workflow

The TENT system is a component-based development using modern software technologies and programming languages (Java, CORBA, XML, Python, WebDAV).

TENT Screenshot TENT

The SikMa Project

The DLR project SikMa (Simulation of Complex Manoeuvres) is under the direction of the DLR institute of Aerodynamics and Flow Technology (AS). The objective is to develop an interactive simulation environment for the simulation of a freely flying, fully configured, elastic warplane. To implement the simulation, the aerodynamic, flight mechanical and aeroelastic equation systems will be calculated for every step, in a time-accurate coupling of aerodynamics, flight mechanics and aeroelasticity.

In addition, the results from the SikMa project will drive the idea of TENT, a uniform simulation environment for DLR, and make a substantial contribution to the DLR core area of the virtual aircraft. Along with the development of the interactive integration environment, and the computing processes and coupling algorithms, the SikMa project will conduct wind tunnel tests. The tests include different models in various manoeuvre scenarios, to obtain a comprehensive data set for the verification and validation of the overall simulation environment.

Experimental aircraft X-31 Air flow in flight around X-31 Typical flight manoeuvre

Provenance and TENT

The following gives an overview of how the Provenance Architecture is used to record information within the workflows of the simulation integration environment TENT. The architecture records three kinds of information:

Interaction P-Assertions

Interactions between system components are recorded as interaction p-assertions. They are used for the ability to restart processes, track user access to data and control user access. In case of a computational job being rejected (by a utilized batch system or Grid) the system has to recognize and record this to the provenance store, and notify TENT for re-submission of the job. Workflow control information and data interchange between system components as well as input files for both - CFD and aero-elastic codes - need to be identified and recorded.

Relationship P-Assertions

Interaction p-assertions between participating components and actors of a process are vital for the documentation of process. But additional information is needed to connect these interactions through causality or other relationships to yield a continuous chain of pieces of information to fully describe the processe's and data provenance. Relationship p-assertions achive this by recording the relationships between a component's inputs and outputs.

Actor State P-Assertions

For reasons of reproducibility, version information about the algorithms used and computational codes must be tracked along with the data itself. This form of information is recorded in actor-state p-assertions.

Workflow diagramm with different assertions

Provenance Queries

The process documentation recorded precisely documents processes. This leads to the possibility to ask questions about the provenance of a processes recorded for analysis purposes. In the following a set of potentially useful provenance queries are presented that makes use of the previosuly recorded process documentation.

For a better understanding, disambiguities on the terminology must be clarified. Previously only the synonym "simulation" has been used. As a simulation may be run using varying parameters and configurations, to distinguish between simualtions, the term "case" is be used to identify a particular configuration of an aerodynamic simulation. This includes the configuration of relevant aerodynamic parts in a certain physical arrangement, and prescribed by specific physical boundary conditions. Every case may be simulated multiple times with changing boundary conditions and possibly changing geometries (e. g. flap settings).

  • Given a certain item of result data, from which case has it been obtained?

  • What is the history of a given data item?

  • Given a certain configuration, how often has it been simulated?

  • How many/what data items have been obtained as the result of a configuration?

  • Given a certain aerodynamic part, from which cases has this part been simulated?

  • Given certain boundary conditions, in which cases have they been applied?

Relationship Query Result


For the aerospace application, the integration of the Provenance Architecture has the following benefits:

  • A clean documentation of simulation workflows that are distributed in multiple/separated network domains and of properties of used resources.

  • The ability to analyze and reason over all conducted computations. This includes the ability to compare computations (e. g., for extraction of similarities or differences), the ability to easily retrace and understand computations and their results, and the possibilty to support the analyses using tools.

  • It allows checking for requirements. For example, it allows checking for compliance to legal and business regulations, or conformance to internal research standards ("Best Practices").