CFD and CFD-Based Optimization in Aerodynamic High-Lift Design

Computational Fluid Dynamics (CFD) found its way into aircraft design starting with the important contributions of A. Jameson in the late 1980’s. First, Euler methods were implemented and in the 1990’s with the rise of the Reynolds-averaged Navier-Stokes (RANS) methods and the growing availability of high-preformance computers (HPC) mathematical optimization. A recent review on the spread of CFD in aircraft design has been provided by Martins. Anyhow, this summary concentrates on overall aircraft and curise flight design. In high-lift system design, numerical optimization based on RANS-CFD for multi-element airfoils was introduced by Eyi et al. and validated as design method by the author. A review on the role of computational methods in high-lift deisgn was presented at that time by van Dam. The first application of numerical optimization on a full 3D aircraft wing was reported by Brezillon et al. in 2008 followed by a kind of design challenge decribed by Iannelli et al. . Nevertheless, full 3D numerical optimization based on RANS is not as established for the high-lift wing as it is for the cruise condition – and this for good reasons. The lecture attempts to give some insight into some recent experience on the use of CFD methods in high-lift design, both for classical aircraft configurations or for more challenging new architectures of high-lift systems

CFD and CFD-Based Optimization in Aerodynamic High-Lift Design

Computational Fluid Dynamics (CFD) found its way into aircraft design starting with the important contributions of A. Jameson in the late 1980’s. First, Euler methods were implemented and in the 1990’s with the rise of the Reynolds-averaged Navier-Stokes (RANS) methods and the growing availability of high-preformance computers (HPC) mathematical optimization. A recent review on the spread of CFD in aircraft design has been provided by Martins. Anyhow, this summary concentrates on overall aircraft and curise flight design. In high-lift system design, numerical optimization based on RANS-CFD for multi-element airfoils was introduced by Eyi et al. and validated as design method by the author. A review on the role of computational methods in high-lift deisgn was presented at that time by van Dam. The first application of numerical optimization on a full 3D aircraft wing was reported by Brezillon et al. in 2008 followed by a kind of design challenge decribed by Iannelli et al. . Nevertheless, full 3D numerical optimization based on RANS is not as established for the high-lift wing as it is for the cruise condition – and this for good reasons. The lecture attempts to give some insight into some recent experience on the use of CFD methods in high-lift design, both for classical aircraft configurations or for more challenging new architectures of high-lift systems

Optimierung der Tragfähigkeit von Zahnwellenverbindungen

In diesem Open-Access-Buch wird gezeigt, dass die Tragfähigkeit evolventisch basierter Zahnwellenverbindungen auf geradezu revolutionäre Art und Weise gesteigert werden kann, wenn für ihre Realisierung nicht das System zur Bezugsprofilgenerierung der [DIN 5480], sondern das in dieser Dissertation neu entwickelte, hoch innovative System zur Profilgenerierung zugrunde gelegt wird. Mit ihm werden, wie mit umfangreichsten Studien belegt wird, die Gestaltfestigkeitsgrenzen nicht nur verschoben, sondern völlig neu definiert. Des Weiteren werden Näherungsgleichungen zur Beschreibung der für das Kriterium der Gestaltfestigkeit optimalen Geometrien sowie für ihre zur nennspannungsbasierten Auslegung erforderlichen Grundgrößen entwickelt. Diese vereinfachen die optimale Ausführung evolventisch basierter Zahnwellenverbindungen außerordentlich. Darüber hinaus wird widerlegt, dass alternative Profilformen, die in der Regel erhebliche wirtschaftliche Nachteile haben, Tragfähigkeitsvorteile aufweisen. Mit dem neuen System zur Profilgenerierung ist nicht nur das volle Potenzial evolventisch basierter Zahnwellenverbindungen erschlossen, sondern zudem deren Anpassung an die an sie gestellten Anforderungen respektive Versagenskriterien möglich

Advanced CFD Applications for Complex Aircraft Configurations

The applied aerodynamics analysis of transport aircraft still poses high challenges on the capabilities of numerical simulations. In past years, this series of STS focused specifically on the high-lift regime, where the demand on accurately predicting stall onset achieved to a sophisticating level. Nowadays, new challenges arise with the progress on active flow control technologies and load control as well as new types of propulsion. This issue of the STS is intended to provide insight into such activities tackling the improvement of simulation capabilities for complex aircraft configurations, as there are: • low-speed assessment of different propulsion concepts; • unsteady active flow control for load alleviation; • simulation of strut-braced wing aircraf

Intervening Metal Systems in GRB and QSO sight-lines: The Mgii and Civ Question

Prochter et al. 2006 recently found that the number density of strong intervening 0.5<z<2 MgII absorbers detected in gamma-ray burst (GRB) afterglow spectra is nearly 4 times larger than in QSO spectra. We have conducted a similar study using CIV absorbers. Our CIV sample, consisting of a total of 20 systems, is drawn from 3 high resolution and high to moderate S/N VLT/UVES spectra of 3 long-duration GRB afterglows, covering the redshift interval 1.6< z<3.1. The column density distribution and number density of this sample do not show any statistical difference with the same quantities measured in QSO spectra. We discuss several possibilities for the discrepancy between CIV and MgII absorbers and conclude that a higher dust extinction in the MgII QSO samples studied up to now would give the most straightforward solution. However, this effect is only important for the strong MgII absorbers. Regardless of the reasons for this discrepancy, this result confirms once more that GRBs can be used to detect a side of the universe that was unknown before, not necessarily connected with GRBs themselves, providing an alternative and fundamental investigative tool of the cosmic evolution of the universe.Comment: 21 pages, 4 figures, ApJ accepted, Revised after Referee Repor

Aerodynamic design of a folded kruger device for a hlfc wing

This work presents the design of a folded Krüger device under realistic geometrical requirements for a wing with hybrid laminar flow control (HLFC). A focus is laid on the investigation of the trade-off between space allocation of the retracted Krüger and the aerodynamic high-lift performance. The results reveal that the Krüger device is able to replace a reference slat device in relation to its aerodynamic high-lift performance. Further on the reduction of the allocation space influences the high-lift performance unfavorably. Document type: Part of book or chapter of boo

Cooperative Concurrent Design Optimization of a Krueger High-Lift System

Within the EU UHURA project , the need emerged to design a folding bull nose Krueger device as the target configuration for studying unsteady aerodynamic effects during deployment and retraction of such a system. Consequently, the design objective of generating as much as possible lift force was subject to the heavy and demanding constraint of being adequately integrated into existing wind tunnel models. Hence, the design specifications require a high-performance Krueger device that doesn't exhibit artificial flow effects besides offering high-performance. This constraint is more important than getting the ultimate performance in terms of maximum lift. As a starting point, the design experience obtained in previous projects, DeSiReH and AFLoNext, has been used to generate an initial Krueger shape. Hence, the characteristic design parameters of the Krueger device obtained in DeSiReH have been mapped to the DLR-F15-LLE geometry. The design of the Krueger flap has been obtained by a cooperative concurrent engineering approach between two UHURA partners, namely CIRA and DLR, in an iterative process. In a first loop, independent optimizations were performed based on the partner's best practice methods. Afterwards, the designs were merged by selecting beneficial aspects of both optimization results. Finally, the design was adapted to respect refined kinematics constraints. The synthesized design achieves all requirements from kinematics and achieves a high level of maximum lift coefficient. For the final design, aerodynamic forces have been derived for the Krueger panel and the bull-nose to support kinematics sizing

Cooperative Concurrent Design Optimization of a Krueger High-Lift System

Within the EU UHURA project , the need emerged to design a folding bull nose Krueger device as the target configuration for studying unsteady aerodynamic effects during deployment and retraction of such a system. Consequently, the design objective of generating as much as possible lift force was subject to the heavy and demanding constraint of being adequately integrated into existing wind tunnel models. Hence, the design specifications require a high-performance Krueger device that doesn't exhibit artificial flow effects besides offering high-performance. This constraint is more important than getting the ultimate performance in terms of maximum lift. As a starting point, the design experience obtained in previous projects, DeSiReH and AFLoNext, has been used to generate an initial Krueger shape. Hence, the characteristic design parameters of the Krueger device obtained in DeSiReH have been mapped to the DLR-F15-LLE geometry. The design of the Krueger flap has been obtained by a cooperative concurrent engineering approach between two UHURA partners, namely CIRA and DLR, in an iterative process. In a first loop, independent optimizations were performed based on the partner's best practice methods. Afterwards, the designs were merged by selecting beneficial aspects of both optimization results. Finally, the design was adapted to respect refined kinematics constraints. The synthesized design achieves all requirements from kinematics and achieves a high level of maximum lift coefficient. For the final design, aerodynamic forces have been derived for the Krueger panel and the bull-nose to support kinematics sizing

Development of a passive-adaptive slat for a wind turbine airfoil

A passive-adaptive slat concept was designed to avoid separation in the root region of a horizontal-axis wind turbine blade. This concept incorporates an autonomously moveable slat device only driven by the aerodynamic forces acting on it without the need for mechanical or electrical actuation. It opens at high local angles of attack to delay the stall angle and closes for small angles of attack to increase the lift to drag ratio of the blade segment. This article describes the development of a passive-adaptive slat for a DU-91-W2-250 airfoil, which is a segment of the reference rotor blade in the project SmartBlades 2.0. In the course of the passive-adaptive slat design, the optimization of the slat and its extended position is presented. This is followed by the development of two passive-adaptive slat kinematics, which are opening and closing the slat passively at different angles of attack. With the designed passive-adaptive slat the stall of the airfoil is delayed by 20 degree in incidence and the maximum lift of the airfoil is increased by about 130 percent at the same time in comparison to the original airfoil. Furthermore, the DU-91-W2-250 airfoil with moveable passive-adaptive slat has in most conditions a higher climb index and therefore a better aerodynamic performance than the same airfoil with a fixed integrated slat