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In order to reduce the weight and improve aerodynamic characteristics, the new aircraft generally adopts lightweight composite materials and high-aspect-ratio layout. Such the structural layout aircraft will produce large nonlinear aeroelastic deformation under the action of aerodynamic loads. Due to the anisotropy of the composite, the composite ply angle of wing skin has a great influence on the elastic deformation of the high-aspect-ratio wing. In order to study the influence of the ply angle on the nonlinear static aeroelastic wing deformation, based on CFD/CSD unidirectional fluid-solid coupling, the structural deformation and stress of high-aspect-ratio composite wing were numerically solved. The wing deformation along the lift direction was taken as the optimization target. The structure strength was taken as the constraint. The ply angle for the composite skin of the high-aspect-ratio composite wing was optimized by the Screening method. The optimization results show the nonlinear static aeroelastic deformation of the wing in the lift direction is reduced by 39.1 %. The maximum stress of the wing beam and rib is reduced by 39.0 %. The maximum Tsai-Wu failure factor of the wing skin is reduced by 47.1 %.

The aerodynamic performance of flexible flapping wing is investigated through numerical simulation based on fluid-structure coupling method, which is developed on the Navier-Stokes equations and structural dynamic equations. The interface data exchange method is based on radial basis function and the moving mesh generation method is based on infinite interpolation. The flexible flapping wings we investigated are constructed of a carbon fiber skeleton and a thin extensible membrane in a bird like scale with the chord Re of 5e4. This research focused on the influence of different flexibilities with same wing structure topology. The flexibility is controlled by diameters of carbon fiber skeleton and five structures are analyzed. The simulation results proved that the structural deformation has a significant effect on the aerodynamic force, especially on the thrust. A wing with maximum rigidity has the best lift performance but the worst thrust performance, and vice versa. A wing with medium rigidity gets better performance in both lift and thrust. According to the results, it is necessary to balance the relations between structure flexibility and aerodynamic performance. Meantime, the characteristics of different structures are consistent with the variety of attack angle and flapping frequency.

The concept of smart morphing blades, which can control themselves to reduce or eliminate the need for active control systems, is a highly attractive solution in blade technology. In this paper, an innovative passive control system based on Shape Memory Alloys (SMAs) is proposed. On the basis of previous thermal and shape characterization of a single morphing blade for a heavy-duty automotive cooling axial fan, this study deals with the numerical analysis of the aerodynamic loads acting on the fan. By coupling computational fluid dynamics and finite element method approaches, it is possible to analyze the actual blade shape resulting from both the aerodynamic and centrifugal loads. The numerical results indicate that the polymeric blade structure ensures proper resistance and enables shape variation due to the action of the SMA strips.

The state of the art of weak fluid-structure coupling for rotors in forward flight at DLR is presented. The coupling procedure is based on the DLR rotor simulation code S4 and the DLR Navier–Stokes solver for structured grids FLOWer. The method allows trimmed CFD solutions to be produced for rotors in high-speed forward flight with the inclusion of elastic blade deformations and viscous effects. The weak coupling procedure is applied to high-speed forward flight test cases of isolated rotors. 4-bladed rotors are simulated for two cases (7A and 7AD rotor) using the chimera approach. A variation of turbulence models from algebraic to 2-equation models did not show significant differences for these high-speed forward flight test cases with moderate rotor loading. The weak coupling, which includes the transfer of normal forces ( c n ), tangential forces ( c t ) and pitching moments ( c m ) from the CFD code to the rotor simulation code, considerably improved the overall agreement with the existing experimental data compared to the uncoupled computations. The performance difference between the 7A and the 7AD rotor in high-speed forward flight is well predicted.

This article presents the development and application of a high-fidelity simulation process chain for commercial aircraft wing multidisciplinary optimization. Based upon a parametric CAD model the aerodynamic coefficients of the wing are determined through solving the Reynolds-averaged Navier–Stokes equations within a numerical flow simulation. Structural mass and elastic characteristics of the wing are determined from structural sizing of the wing box for essential load cases by usage of the finite element method. The interactions between the aerodynamic forces and the structural deformation of the elastic wing are taken into account in the process chain by fluid-structure coupling. To reduce the number of design variables, the design task is solved by a two-step approach. To design the inner wing, an optimization of the inner airfoil geometry and the wing twist with the lift-to-drag ratio as objective function has been conducted in the first step. Based on the inboard airfoil of this optimized inner wing, multidisciplinary optimizations of the wing planform have been performed in the second step. These optimizations include the wing twist and thickness distribution in span direction as design parameters but maintain airfoil shapes. A deterministic optimization method has been applied to locate the optimum within the design space. Range and efficiency, in terms of fuel consumption per range and payload, were used as objective functions in the wing planform multidisciplinary optimizations. Two approaches for the determination of the aerodynamic loads for the 2.5-g maneuver load case based on the aerodynamic loads under cruise flight conditions have been investigated. Both approaches have been integrated in the process chain for multidisciplinary wing optimization and have been used for the wing optimization of a long-range aircraft with backward swept wings. The results of the corresponding wing optimizations have been compared with each other.

A partitioned fluid-structure coupling code for transonic panel flutter has been developed and validated. The Reynolds-averaged Navier-Stokes equations are solved numerically by means of an implicit finite volume method to account for nonlinear aerodynamics, as there are shock waves and a viscous boundary layer at the panel surface. An implicit finite element formulation of the structural equations as well as a Galerkin solution of the von-Karman plate equation are employed to solve elastic panel deformations with respect to geometric nonlinearities. A detailed validation process is presented in this paper for high subsonic and low supersonic Mach numbers. This comprises a discussion of available results from literature with the objective to propose a guideline for validation purposes of partitioned panel flutter solvers. Thereupon the code is used for studies on the impact of turbulent boundary layer characteristics on aeroelastic stability boundaries and post-flutter. An evaluation of flutter modes and frequencies in the post-flutter domain as well as a discussion of the corresponding flow phenomena is presented.

The aeroelastic behaviour of vibrating blade assemblies is usually investigated in the frequency domain where the determination of aeroelastic stability boundaries is separated from the computation of linearized unsteady aerodynamic forces. However, nonlinear fluid-structure interaction caused by oscillating shocks or strong flow separation may significantly influence the aerodynamic damping and hence effect a shift of stability boundaries. In order to investigate such aeroelastic phenomena, the governing equations of structural and fluid motion have to be simultaneously integrated in time. In this paper a technique is presented which analyzes the aeroelastic behaviour of an oscillating compressor cascade in the time domain. The structural part of the governing aeroelastic equations is time-integrated according to the algorithm of Newmark, while the unsteady airloads are computed at every time step by an Euler upwind code, The link between the two time integrations is an automatic grid generation in which the used mesh is dynamically deformed as such that it conforms with the deflected blades at every time step. The computed time series of the aeroelastic simulation of an assembly of twenty compressor blades performing torsional vibrations in transonic flow are presented. For subsonic flow, the differences between time domain and frequency domain results are of negligible order. For transonic flow, however, where vibrating shocks and a temporarily choked flow in the blade channel dominate the unsteady flow, the energy transfer between fluid and structure is no longer comparable to that of a linear system. It is demonstrated that the application of the time domain method leads to a significantly different aeroelastic behaviour of the blade assembly including a shift of the stability boundary.

The influence of the planform shape of osculating cones waveriders on the aerodynamic behavior with respect to the longitudinal motion is discussed. The inviscid flowfield around the configurations is simulated along the complete trajectory of an airbreathing two-stage-to-orbit system based on the solution of the Euler equations. Grid refinement studies, as well as wind-tunnel results, are presented to demonstrate the validation and accuracy of the code. Furthermore, special attention is drawn to the fluid-structure interaction with respect to the heating of the leading edge under hypersonic flight conditions. It is found that the modification of a gothic planform toward combined forebody-delta wing planforms allows a significant improvement of the aeordynamic efficiency L/D in sub- and transonic flows. In addition, the longitudinal stability is increased without compromising the favorable high-speed qualities. These benefits are partly diminished by an increasing neutral point shift along the trajectory. In Part 2 (Heinze, W., and Bardenhagen, A., "Waverider Aerodynamics and Preliminary Design for Two-Stage-to Orbit Missions, Part 2," Journal of Spacecraft and Rockets, Vol. 35, No. 4, 1998, pp. 459-466), the impact of the aerodynamic effects on the integrated design and performance of a waverider-based two-stage.to-orbit system is presented.

The presented investigations deal with the analysis of dynamic derivatives of a modern transport aircraft configuration (DLR-F12). The conducted wind tunnel tests focused mainly on the measurements of unsteady forces, moments and pressure distributions. The measurements of the steady and unsteady wing deformations using two different wings were of significant importance. Those wings are designed to be ideal stiff on the one hand but also to allow more flexibility on the other hand, in order to investigate the effect of wing elasticity on the static and dynamic aerodynamic properties of this configuration. For the validation of the numerical tools calculations are performed based on the solution of the unsteady Reynolds-averaged Navier-Stokes (URANS) equations using a finite volume parallel solution algorithm with an unstructured discretization concept (DLR TAU-Code). The wing deformation is accounted for using the finite element code ANSYS.

In this paper, the problem of sailing yacht rig design has been addressed through the development of a computational framework based on viscous Computational Fluid Dynamic (CFD) modelling for the aerodynamic part and on a non linear structural modelling for the structure part. The Fluid Structure Interaction (FSI) coupling used is a loose coupling. The interest but also the expertise needed to use Reynolds Averaged Navier-Stokes (RANS) equations for the aerodynamic modelling is justified through examples and validations with a focus on complex separated flow configurations. The originality of the presented computational framework is its ability to address complex, non linear optimization problems with a derivative free evolutionary strategy. This capability is enhanced by the fact that it is based on a remeshing technique rather than on a deforming mesh one. After the description of the main elements of this computational framework for Fluid Structure Interaction, it is used for generic sail optimization problems and for the rig design of a 18 footer to illustrates its capabilities and limitations to produce accurate aeroelastic solutions on sailing yacht rigs.

Here is presented an overview of the hypersonic experiment on sharp edge concepts, SHEFEX-I. The project, being performed under responsibility of the German Aerospace Center (DLR), is aimed to investigate the behavior and the possibilities of an improved shape for aerospace vehicles considering sharp edges and facetted surfaces. It is a basic in-flight experimentation research on hypersonic technologies for future launcher vehicles but not a re-entry experiment. Additionally, the SHEFEX-I project is the starting point for a series of experiments which enable the acquisition of important knowledge in hypersonic free flight experimentation and which are an excellent test bed for new technological concepts. The experiment which successfully flew on top of a two-stage solid propellant sounding rocket on October 27th, 2005 from Andøya Rocket Range in northern Norway, enabled time accurate investigation of the flow effects and their structural answer during a hypersonic flight Ma~6 from 90 km down to an altitude of 20 km. The present paper gives an overview about the aerothermodynamic philosophy and introduces some main outcomes of the post-flight analysis.