Structural Dynamics Modeling of HIRENASD in Support of the Aeroelastic Prediction Workshop

An Aeroelastic Prediction Workshop (AePW) was held in April 2012 using three aeroelasticity case study wind tunnel tests for assessing the capabilities of various codes in making aeroelasticity predictions. One of these case studies was known as the HIRENASD model that was tested in the European Transonic Wind Tunnel (ETW). This paper summarizes the development of a standardized enhanced analytical HIRENASD structural model for use in the AePW effort. The modifications to the HIRENASD finite element model were validated by comparing modal frequencies, evaluating modal assurance criteria, comparing leading edge, trailing edge and twist of the wing with experiment and by performing steady and unsteady CFD analyses for one of the test conditions on the same grid, and identical processing of results

The effects of response probability on commission errors in high go low no-go dual response versions of the sustained attention to response task (SART)

In the current investigation, we modified the high Go low No-Go Sustained Attention to Response Task (SART) by replacing the single response on Go trials with a dual response (dual response SART or DR SART). In three experiments a total of 80 participants completed the SART and versions of the DR SART in which response probabilities varied from 50-50, through 70-30 to 90-10. The probability of No-Go withhold stimuli was .11 in all experiments. Using a dynamic utility based model proposed by Peebles and Bothell (2004) we predicted that the 50-50 DR-SART would dramatically reduce commission errors. Additionally, the model predicted that the probability of commission errors to be an increasing function of response frequency. Both predictions were confirmed. Although the increasing rate of commission errors with response probability can also be accommodated by the rationale originally proposed for the SART by its creators (Robertson, Manly, Andrade, Baddeley, & Yiend, 1997) the fact that the current DR SART results and SART findings in general can be accommodated by a utility model without need for any attention processes is a challenge to views that ascribe commission errors to lapses of sustained attention

Plans for Aeroelastic Prediction Workshop

This paper summarizes the plans for the first Aeroelastic Prediction Workshop. The workshop is designed to assess the state of the art of computational methods for predicting unsteady flow fields and aeroelastic response. The goals are to provide an impartial forum to evaluate the effectiveness of existing computer codes and modeling techniques, and to identify computational and experimental areas needing additional research and development. Three subject configurations have been chosen from existing wind tunnel data sets where there is pertinent experimental data available for comparison. For each case chosen, the wind tunnel testing was conducted using forced oscillation of the model at specified frequencie

Kopplungswerkzeuge für aeroelastische Simulationen

The direct numerical simulation of fluid-structure-interaction has received a lot of attention in recent years. Due to the growing size of planned commercial airplanes and the widespread use of lightweight-structures leading to large elastic deflections in flight, great interest of commercial applications of such simulation techniques has developed. The currently used simplified methods to estimate the stresses on the structure of a flying plane are not suitable any more, when a new highly elastic airplane is considered, since the complex interaction between fluid and structure is usually highly nonlinear. Here the need arises to use a direct simulation of the whole coupled, aeroelastic system. A set of tools to calculate these simulations reusing existing numerical flow-solvers is developed in this work. The coupling algorithm used treats the flow and the structure dynamics in the sense of an area separation. This leads to a set of separated solvers for each area and the development of a suitable data-exchange strategy. When the flight vehicle gets deformed due to aerodynamic (or other) loads, then it will be neccessary for the calculation grid of the flow solver to follow the deforming shape continously. An essential part of this work describes a novel technique to reshape the calculation mesh according to elastic deformation of the flight vehicle. Certain lines of the mesh were modeled as elastic beams, fixed on nodes to form an elastic framework, which will help to ensure grid deformations with good quality regarding intersection angles of gridlines at reasonable calculation costs. Although suited for any type of mesh, an implementation for structured multi-block grids, as used by the flow-solver FLOWer, is presented, which proved reliable in practical use even for complex geometries. The elastic flight vehicle is modeled via a finite-elemet-method using a set of simple elements, mainly beams, where the elastic structure is reduced to a few, simple components. Of great importance for the correct reproduction of the physics of the whole coupled aeroelastic system is the exchange of loads from fluid to structure on one hand and the transfer of strucutral deflections to the boundary-conditions of the flow-solver on the other hand. Further the possibility to simulate a free flight (i.e. plane-model not fixed in a wind-tunnel) is implemented. A new coordinate-system needs to be invented here, which moves with the vehicle accordingly, so that the calculation of elastic deformation and flow can be done inside the new, moved coordinate-system

Supporting Online Updates of Software Product Lines : A Controlled Experiment

The evolution of Software Product Lines (SPL) is challenging because stakeholders have to deal with both regular evolution and the co-existence of different products. Our focus of product evolution is on the tasks integrators have to perform to update deployed SPL products with minimal interruption of services. In case of Egemin, our industrial partner, the updates of SPL products is further hampered as a consequence of outdated and imprecise architectural knowledge of deployed products. To facilitate the updates of products, we have developed the architecture-centric approach which comprises two complementary parts: an update viewpoint and a supporting tool. In this paper we present an evaluation of the architecturecentric approach. The approach is compared with the Egemin's current update approach in a controlled experiment. In the experiment 17 professionals were asked to perform 68 updates of logistic systems. The results obtained from the experiment show that the architecture-centric approach significantly improves the correctness of updates and reduces the interruption of services during updates of Egemin's SPL products

On-demand Generation of Views to Support Online Evolution of Software Product Lines

It is difficult to achieve assured conformance between architecture and code. We lacked proper architecture descriptions in the context of the evolution of an industrial software product line of logistic systems. As a result, a lack of explicit architecture documentation about the deployed products led to ad hoc update practices, which were error prone and resulted in unnecessary and undesirable shutdowns. To tackle these problems, we have codified the architecture knowledge required for evolving products in a viewpoint. Based on this viewpoint, we developed a supporting tool that allows generating on-demand architecture models. These models guide maintainers by listing the concrete tasks they need to perform when upgrading a system and by showing inconsistencies when they fail to do so. The evaluation of 68 updates of industrial logistic systems demonstrates a significant improvement in the quality of system updates with respect to the correct execution of updates and a reduced interruption of services

An Architectural Approach to Support Online Updates of Software Product Lines

Despite the successes of software product lines (SPL), managing the evolution of a SPL remains difficult and error-prone. Our focus of evolution is on the concrete tasks integrators have to perform to update deployed SPL products, in particular products that require run-time updates with minimal interruption. The complexity of updating a deployed SPL product is caused by multiple interdependent concerns, including variability, traceability, versioning, availability, and correctness. Existing approaches typically focus on particular concerns while making abstraction of others, thus offering only partial solutions. An integrated approach that takes into account the different stakeholder concerns is lacking. In this paper, we present an architectural approach for updating SPL products that supports multiple concerns. The approach comprises of two complementary parts: (1) an update viewpoint that defines the conventions for constructing and using architecture views to deal with multiple update concerns; and (2) a supporting framework that provides an extensible infrastructure supporting integrators of a SPL. We evaluated the approach for an industrial SPL for logistic systems providing empirical evidence for its benefits and recommendations