Dieter Kohlgrüber

Fuselage Structures within the CPACS Data Format

Purpose This paper aims to summarize the main features of the fuselage structure description within the Common Parametric Aircraft Configuration Schema (CPACS) data format. Design/methodology/approach The CPACS fuselage structure description includes the definition of arbitrary sheets and structural profiles which can be combined with a variety of material definitions to so-called structural elements. Besides the definition of these structural elements, the definitions of structural members, such as stringers, frames, floor structures and pressure bulkheads, as well as the definitions of the complex load introduction regions that transfer loads from the wings and the empennage into the fuselage shell are introduced. Finally, exemplary models generated with different mesh generation tools developed at the DLR Institute of Structures and Design are presented. These models are suitable for subsequent static or dynamic structural analyses. Findings The CPACS fuselage structure description is suitable for defining standard fuselage configurations including complex load introduction regions suitable for different types of structural analysis. Practical implications The work shows exemplary fuselage models generated from the introduced CPACS fuselage description suitable for subsequent static and dynamic structural analyses. As the CPACS standard is available for download, the described definitions may be used by universities, research organizations or the industry. Originality/value The work presents the definitions of the fuselage structure within the CPACS schema that were mainly developed by the authors employed at the DLR Institute of Structures and Design. The exemplary applications show models generated completely on the basis of the definitions described in this paper.

Advances in Numerical Ditching Simulation of Flexible Aircraft Models

Abstract This paper deals with explicit numerical simulation of fixed-wing aircraft ditching using a coupled approach of Smoothed Particle Hydrodynamics and Finite Elements. Particular focus is put on recent advances toward simulation of flexible full aircraft models, which comprises significant challenges with respect to the numerical efficiency as well as the model complexity. First, the pursued numerical approach is briefly presented. In order to deal with aforementioned challenges, an automated modular tool, which generates numerical models and launches ditching simulations, is presented. The paper provides a brief explanation of state-of-the-art aircraft as well as fluid modelling techniques used and furthermore presents an integrated model that computes aerodynamic loads during the simulation. The developed tool is used to conduct various numerical studies. First, the improved efficiency of such simulations over the state of the art is shown. Next, results of parameter studies are presented, demonstrating the effects of impact conditions on the aircraft motion. Finally, the structural deformation experienced during ditching of a detailed finite element aircraft model is analysed and its effects on the aircraft motion are discussed.

Modeling of CPACS-based fuselage structures using Python

Purpose The purpose of this paper is to present some of the key achievements. At DLR, a sophisticated interdisciplinary aircraft design process is being developed, using the CPACS data format (Nagel et al., 2012; Scherer and Kohlgruber, 2016) as a means of exchanging results. Within this process, TRAFUMO (Scherer et al., 2013) (transport aircraft fuselage model), built on ANSYS and the Python programming language, is the current tool for automatic generation and subsequent sizing of global finite element fuselage models. Recently, much effort has gone into improving the tool performance and opening up the modeling chain to further finite element solvers. Design/methodology/approach Much functionality has been shifted from specific routines in ANSYS to Python, including the automatic creation of global finite element models based on geometric and structural data from CPACS and the conversion of models between different finite element codes. Furthermore, a new method for modeling and interrogating geometries from CPACS using B-spline surfaces has been introduced. Findings Several new modules have been implemented independently with a well-defined central data format in place for storing and exchanging information, resulting in a highly extensible framework for working with finite element data. The new geometry description proves to be highly efficient while also improving the geometric accuracy. Practical implications The newly implemented modules provide the groundwork for a new all-Python model generation chain, which is more flexible at significantly improved runtimes. With the analysis being part of a larger multidisciplinary design optimization process, this enables exploration of much larger design spaces within a given timeframe. Originality/value In the presented paper, key features of the newly developed model generation chain are introduced. They enable the quick generation of global finite element models from CPACS for arbitrary solvers for the first time.