Reliability-Based Design Optimization of Nonlinear Aeroelasticity Problems

Missoum, Samy; Dribusch, Christoph; Beran, Philip S.

doi:10.2514/1.46665

Cited by 40 publications

(22 citation statements)

References 22 publications

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“…(25), some specific LCO amplitude (tip twist, for example) at a fixed flight speed, or some combination of these parameters may provide a superior structure. Finally, the effect of uncertainties needs to be accounted for in the design process, as LCO behavior has been shown to be susceptible to stochastic environments (Ghommem et al, 2010;Missoum et al, 2010;Sarkar et al, 2009;Stanford and Beran, 2012;Thomas et al, 2006). The direct method may be well suited to sampling-based techniques, as well as approximation schemes (first order reliability methods, e.g.)…”

Section: Discussionmentioning

confidence: 99%

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Direct flutter and limit cycle computations of highly flexible wings for efficient analysis and optimization

Stanford

Beran

2013

Journal of Fluids and Structures

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a b s t r a c tThe usefulness of flutter as a design metric is diluted for wings with destabilizing (softening) nonlinearities, as a stable high-amplitude limit cycle (subcritical) may exist for flight speeds well below the flutter point. It is thus desired to design aeroelastic structures such that the post-flutter behavior is as benign (i.e., supercritical) as possible, among the other constraints commonly considered in the optimization process. In order to account for these metrics in an accurate and efficient manner, direct tools are utilized to first locate the Hopf-point (flutter speed), and then to obtain a nonlinear perturbation solution via the method of multiple scales. The latter scheme provides a scalar variable whose sign and magnitude dictate the nature of the limit cycle. The accuracy of these methods is demonstrated with a high-aspect-ratio highly flexible wing, modeled with nonlinear beam finite elements and the ONERA dynamic stall tool. Stiffness and inertial design variables are allowed to vary spatially throughout the wing, in order to conduct gradient-based optimization of the limit cycle under flutter and mass constraints. The resulting wing structure demonstrates strongly supercritical behavior, as well as several design conflicts between linear (flutter) and nonlinear (limit cycles) sensitivities, which are not present in the uniform baseline wing.Published by Elsevier Ltd.

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Section: Discussionmentioning

confidence: 99%

“…Such examples are rare in the literature, see Palaniappan et al (2006), Missoum et al (2010), and Stanford and Beran (2012). One reason for this scarcity is that limit cycle computations are very expensive, and thus not amenable to the repeated function evaluations and sensitivity analysis required for gradient-based optimization.…”

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confidence: 99%

Direct flutter and limit cycle computations of highly flexible wings for efficient analysis and optimization

Stanford

Beran

2013

Journal of Fluids and Structures

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“…The airfoil can exhibit sub-critical LCO which happen at lower speed that the predicted linear flutter velocity (FIgure 3.1). By using clustering techniques, the discontinuities can be detected, thus providing the classification to construct the explicit sub-critical LCO boundary [2].…”

Section: Methodology and Accomplishmentsmentioning

confidence: 99%

“…For instance, we have solved a problem where one wants to minimize weight while making sure that subcritical LCOs do not appear with a given probability [2]. A new approach has also been developed to obtain a relatively conservative probability of failure using probabilistic support vector machines [3].…”

Section: Methodology and Accomplishmentsmentioning

confidence: 99%

Computational Design Optimization Under Uncertainty of Systems with Nonlinear Aeroelastic Constraints

Missoum¹

2012

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Standard Form 298 (Rev. 8/98) REPORT DOCUMENTATION PAGEPrescribed by ANSI Std. Z39.18 Form Approved OMB No. 0704-0188The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to the Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

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“…Convex hulls were used by Scarth et al (2014) to partition the space of random variables in accordance with the feasible types of aeroelastic instability, in order to fit multiple Polynomial Chaos Expansion surrogate models. Support Vector Machines, a type of surrogate model used to emulate discrete-valued functions, were used by Missoum et al (2010) to estimate the reliability of two degree of freedom aerofoils undergoing limit cycle oscillations, in the minimisation of an uncertain, nonlinear stiffness term. Additionally, Becker et al (2013) developed an approach in which classification and regression trees were used in conjunction with Gaussian Process Emulators to emulate bifurcating systems.…”

Section: Introductionmentioning

confidence: 99%

Reliability-based aeroelastic design of composite plate wings using a stability margin

Scarth

Cooper

2017

Struct Multidisc Optim

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Reliability-based design is concerned with ensuring that constraints are enforced with acceptable probability under inherent variability in properties. In aircraft design, such a constraint may be that aeroelastic instability does not occur at velocities encountered by the aircraft. This approach can be complicated, as the aeroelastic instability speed is a discontinuous function of material properties, on account of particular modes only becoming unstable for some parameter values. In reliability analysis, it is common to use surrogate models due to the computational expense associated with Monte Carlo Simulation, however, such methods can be inaccurate when emulating discontinuous functions such as the aeroelastic instability speed. In this paper, an alternative approach is proposed in which Gaussian process surrogate models are fitted directly to each of the modal eigenvalues at the design air-speed, and used to emulate a stability margin based upon the most critical eigenvalue. Using this approach, it is shown that the reliability may be estimated for the aeroelastic stability using smooth emulators, thereby overcoming the problems associated with discontinuities. The method is demonstrated for layup optimisation of composite plate wings with uncertain ply angles, in which the probability of aeroelastic instability occurring is minimised for a prescribed air-speed. In uncertainty quantification, a good agreement is found with Monte Carlo Simulation with an order of two magnitudes reduction in model runs. Through reliability-based design, reductions in the probability of failure of up to 99.8% are achieved by increasing the stability margin at the design speed.

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Reliability-Based Design Optimization of Nonlinear Aeroelasticity Problems

Cited by 40 publications

References 22 publications

Direct flutter and limit cycle computations of highly flexible wings for efficient analysis and optimization

Direct flutter and limit cycle computations of highly flexible wings for efficient analysis and optimization

Computational Design Optimization Under Uncertainty of Systems with Nonlinear Aeroelastic Constraints

Reliability-based aeroelastic design of composite plate wings using a stability margin

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