An Integrated Method for Determination of the Oswald Factor in a Multi-Fidelity Design Environment

Aircraft conceptual design often focuses on unconventional configurations like for example forward swept wings. Assessing the characteristics of these configurations usually requires the use of physic based analysis modules. This is due to the fact that for unconventional configurations no sucient database for historic based analysis modules is available. Nevertheless, physic based models require a lot of input data and their computational cost can be high. Generating input values in a trade study manually is work-intensive and error-prone. Conceptual design modules can be used to generate sucient input data for physic based models and their results can be re-integrated into the conceptual design phase. In this study a direct link between a conceptual design module and an aerodynamic design module is presented. Geometric information is generated by the conceptual design module and the physic based results, in form of the Oswald factor, are then fed back. Apart from the direct link, an equation for determination of the Oswald factor is derived via a Symbolic Regression Approach

AIRCRAFT CONFIGURATION ANALYSIS USING A LOW-FIDELITY, PHYSICS BASED AEROSPACE FRAMEWORK UNDER UNCERTAINTY CONSIDERATIONS

During the early stages of aircraft design, limited information is available to conduct decisions that base on the quality of aircraft configurations. In the present study, information on physical and statistical models is supplemented by the uncertainty that is inherent to the applied analysis modules and propagated through the complete design workflow. Using this method, the possibility arises to make a statement on the level of certainty with which one concept is preferred above another

Genetic loci and prioritization of genes for kidney function decline derived from a meta-analysis of 62 longitudinal genome-wide association studies

Estimated glomerular filtration rate (eGFR) reflects kidney function. Progressive eGFR-decline can lead to kidney failure, necessitating dialysis or transplantation. Hundreds of loci from genome-wide association studies (GWAS) for eGFR help explain population cross section variability. Since the contribution of these or other loci to eGFR-decline remains largely unknown, we derived GWAS for annual eGFR-decline and meta-analyzed 62 longitudinal studies with eGFR assessed twice over time in all 343,339 individuals and in high-risk groups. We also explored different covariate adjustment. Twelve genome-wide significant independent variants for eGFR-decline unadjusted or adjusted for eGFR-baseline (11 novel, one known for this phenotype), including nine variants robustly associated across models were identified. All loci for eGFR-decline were known for cross-sectional eGFR and thus distinguished a subgroup of eGFR loci. Seven of the nine variants showed variant-by-age interaction on eGFR cross section (further about 350,000 individuals), which linked genetic associations for eGFR-decline with age-dependency of genetic cross-section associations. Clinically important were two to four-fold greater genetic effects on eGFR-decline in high-risk subgroups. Five variants associated also with chronic kidney disease progression mapped to genes with functional in-silico evidence (UMOD, SPATA7, GALNTL5, TPPP). An unfavorable versus favorable nine-variant genetic profile showed increased risk odds ratios of 1.35 for kidney failure (95% confidence intervals 1.03-1.77) and 1.27 for acute kidney injury (95% confidence intervals 1.08-1.50) in over 2000 cases each, with matched controls). Thus, we provide a large data resource, genetic loci, and prioritized genes for kidney function decline, which help inform drug development pipelines revealing important insights into the age-dependency of kidney function genetics

Evaluation of Modeling Languages for Preliminary Airplane Design in Multidisciplinary Design Environments

The coupling of physical effects and the rising complexity of modern aircraft necessitate an intense collaboration of disciplinary specialists in preliminary airplane design. Additionally, a growing number of suppliers and outsourced design activities aggravate the design processes even further. Novel multidisciplinary design environments intend to enable specialists to better integrate analysis codes and constitute the consistent technical basis for their cooperation. In this manner different technical aspects can be evaluated quickly, since the data update and analysis capabilities are available throughout the design team. The exchange of information is therefore of crucial importance in multidisciplinary design. Due to the fact that in data exchange the number of interfaces is the critical factor for the flexibility of a design environment, a central information model is a key feature. The central information model reflects among other things the common namespace of the design team and can be seen as the meta-model for all of the deduced analysis models. The architecture of such a novel design environment is strongly linked to principles of model-based architectures and the chosen underlying software engineering techniques influence strongly the efficiency of the resulting design processes. An information model for a design environment as described above consists of two aspects. On the one hand the elements, attributes and their structure need to be defined in a schema definition. On the other hand the explicit content has to be stored in a data set conform to the schema definition. Whereas the data set is mainly used for the exchange of information, the schema definition is utilized for documentation, model validation and model generation. Several possibilities of attributes for a quality information model are named in the literature and are outlined in this research. These attributes or requirements include important aspects like holism, accessibility, transparency and ordering mechanisms. Additionally, several abstraction methods need to be taken into account that are mostly based on principles of object oriented modeling. Information models commonly used in preliminary airplane design include STEP, XML and most recently the Unified Modeling Language (UML). The Standard for the Exchange of Product Data (STEP) is described in ISO 10303. STEP is widely spread in the industry. The meta-models are built up using the object flavored modeling language EXPRESS. Content models are stored either via plain text or XML formats. The Common Parametric Aircraft Configuration Schema (CPACS) is a DLR intern standard. It is used in several multidisciplinary projects that handle the scope of preliminary airplane design and further aspects like climate impact and transport systems. The standard is based on XML and benefits from a growing number of tools that are adapted to it. As UML is concerned, there is not yet a standard for the modeling of preliminary aircraft data, this work provides therefore an outlook on some of the research in this area. Traditionally, the UML is a powerful software modeling language and the only of the introduced language concepts that features a truly integrated model. The different modeling languages and approaches are reviewed in respect to the quality characteristics already mentioned. Their development history is displayed and existing approaches for the application of these techniques to preliminary airplane design in the academic as well as industrial field are shown. An evaluation of the named modeling languages is made with respect to the existing multidisciplinary design environment at the DLR. Future developments for the different modeling languages are outlined and potential crossovers highlighted. It is shown that CPACS can be translated to an UML model. Additionally, a CPACS to STEP translator is introduced outlining the software mechanisms applied and showing a validation example using the geometry data of the VFW-614 ATTAS. This research concludes in an evaluation of several techniques for information modeling taken from computer science to a multidisciplinary engineering design environment for preliminary airplane design. The central information model contained therein forms the basis for distributed modeling and simulation. Its proper parameterization allows therefore a more firm and consolidated assessment of known aircraft designs as well as of some of the potential aircraft technologies of tomorrow

Data integration in preliminary Airplane Design

A multidisciplinary approach to preliminary airplane design is seen as one of the major improvements for future design tasks. Several approaches can be found in the literature. The key to a multidisciplinary approach is a central model that contains all data and is accessible for all domains. The goal of this work is to analyze three different models in respect to their benefits for data integration in preliminary airplane design. The models are Cpacs, developed at the Dlr, Step, published by the Iso, and the Uml, released by the Omg. For this purpose a lexical overview of the important terms is given. Additionally several methods for the classification of information are introduced and requirements for information models are set up. The main part of the work is contributed to the analysis of the different models. A conclusion is drawn that suggests a solution for a future information model using a combination of the Uml / SysML and Xml. Subsequently a prototype for a converter tool, that processes Cpacs data to Step is developed. The converted geometry data of the Attas Vfw 614 is used for validation and shows the quality of the tool

Konzeptentwurf von Verkehrsflugzeugen: Anwendung dynamischer Programmiersprachen

In den frühen Phasen des Flugzeugentwurfes müssen aus Anforderungen an eine neue Konfiguration erste Konzepte abgeleitet werden. Hierbei werden in der Regel einfache „Handbuchverfahren“, die auf statistischen Grundlagen basieren, verwendet. Häufig wechselnde Anforderungen und die Integration höherwertiger Ergebnisse zur Steigerung der Aussagegenauigkeit stellen dabei hohe Ansprüche an die Flexibilität und Erweiterbarkeit der eingesetzten Verfahren. Python bietet als dynamische Programmiersprache mehrere Mechanismen zur Implementierung eines solchen Verfahrens. In Rahmen des eingereichten Vortrages soll dies durch einige Anwendungen verdeutlicht werden: • Reflexion: Zur Ableitung der Entwurfsstrategie • Monkey Patch: Zur Anpassung der Entwurfsmethoden • Dynamischer Typisierung: Zur Bestimmung von Sensitivitäten mittels Komplexer Schrittweiten Approximation Die benannten Verfahren sind im Konzeptentwurfstool VAMPzero des Deutschen Zentrums für Luft- und Raumfahrt e.V. implementiert und stehen interessierten Entwicklern frei zur Verfügung

Aircraft Design and an Engineer’s Approach to Software Testing

Software testing is essential to ensure quality standards and guide effective development. Nevertheless, for highly specialized codes conventional testing methods are unsatisfying, as quality goals differ. The talk focuses on two testing methods for engineering applications. These will be applied to a conceptual aircraft design code written in Python. Sensitivity analysis is introduced as a method for unit testing. Additionally, system tests are realized by using a historical aircraft database. For example, an engineer is absolutely fine with a number of passengers equal to 140.7 as long as it results in the desired payload mass. Hence, the requirements for a unit test are: a) if there are 140.7 passengers aboard the aircraft there must be a positive float value for the payload mass and much more important b) if the number of passengers is increased the payload increases as well! While a) can be tested using conventional unit tests, b) can be tested using sensitivity analysis. The results of the sensitivity analysis can be compared to expert knowledge. This knowledge is derived from interviews and coded in simple expression statements. The talk will introduce complex step derivative approximation as means for sensitivity analysis and outlines some first test results. When it comes to system testing, conceptual aircraft design codes need to design aircraft concepts. It is therefore obvious that a database of aircraft characteristics forms suitable test cases. While doing system tests of the code, aircraft characteristics from the database serve as input for the code and the calculation results are compared again to an aircraft performance database. As the code operates on a low level of fidelity one can only tell how far it is off. Nevertheless, good assumptions on the quality of the code and especially on the impact of newly implemented design methods can be made

A Multi-Fidelity Workflow to Derive Physics-Based Conceptual Design Methods

The present study developed a multi-fidelity workflow to derive physics-based conceptual design methods from models of higher-fidelity usually employed during preliminary aircraft design. The multi-fidelity workflow consists of a design of experiments, a multi-fidelity loop, and symbolic regression as surrogate modeling technique. Results are presented for conventional and unconventional aircraft configurations

ANALYSIS OF AIRCRAFT CONFIGURATIONS INCLUDING PROPAGATED UNCERTAINTIES

During early design stages, limited information is available to conduct decisions on the goodness of aircraft configurations. In this work, the physical information is supplemented by the uncertainty underlying the applied analysis modules, propagated through the complete design workflow. Thereby, it is possible to not only state that one concept is preferred above another, but furthermore the level of certainty of such a statement can be quantified