Small Disturbance Navier-Stokes Computations for Low-Aspect-Ratio Wing Pitching Oscillations

Pechloff, Alexander; Laschka, Boris

doi:10.2514/1.45233

Cited by 14 publications

(8 citation statements)

References 18 publications

(25 reference statements)

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“…In this context, a userdefined time law can be prescribed to interpolate between a reference grid and various amplitude grids [11,35]. For further information on the CFD solver framework, the RANS solver, and the respective small disturbance variants, refer to [33,[36][37][38].…”

Section: B Computational Fluid Dynamics: Inviscid Solver Aer-eumentioning

confidence: 99%

Neurofuzzy-Model-Based Unsteady Aerodynamic Computations Across Varying Freestream Conditions

Winter

Breitsamter

2016

AIAA Journal

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This paper presents a reduced-order modeling approach based on recurrent local linear neurofuzzy models for predicting generalized aerodynamic forces in the time domain. Regarding aeroelastic applications, the unsteady aerodynamic loads are modeled as a nonlinear function of structural eigenmode-based disturbances. In contrast to established aerodynamic input/output model approaches trained by high-fidelity flow simulations, the Mach number is considered as an additional model input to account for varying freestream conditions. To train the relationship between the input parameters and the corresponding flow-induced forces, the local linear model tree algorithm is adopted in this work. The proposed method is tested exemplarily with respect to the AGARD 445.6 configuration in the subsonic, transonic, and supersonic flight regimes. It is shown that good conformity is obtained between the reduced-order model results and the respective full-order computational-fluid-dynamics solution. A further comparative analysis in the frequency domain in conjunction with a classical flutter analysis confirms the validity of the approach. Finally, the method's potential for reducing the computational effort of aeroelastic analyses is demonstrated.

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Section: B Computational Fluid Dynamics: Inviscid Solver Aer-eumentioning

confidence: 99%

Neurofuzzy-Model-Based Unsteady Aerodynamic Computations Across Varying Freestream Conditions

Winter

Breitsamter

2016

AIAA Journal

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“…Various results for forced-motion responses have been presented showing excellent agreement within the limits of the method at significantly reduced computational cost. [12][13][14][15] Even for a full civil aircraft at cruise conditions time savings of one to two orders of magnitude are reported. 16 More recently, several authors proposed an extension of the LFD method towards gust response simulations either focussing on the computation of aeroelastic transfer functions 17,18 or on a purely aerodynamic analysis.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Unsteady Reduced Order Models based on Computational Fluid Dynamics for Gust Loads Predictions

Bekemeyer

Ripepi

Heinrich

et al. 2018

2018 Applied Aerodynamics Conference

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A tremendous number of gust load cases needs to be computed during the aircraft design and certification process. From an aerodynamic point of view, gust loads predictions in industry rely on linear potential flow methods which are inappropriate at transonic flight conditions. Prediction accuracy can be enhanced by accounting for aerodynamic loads computed with computational fluid dynamics, eventually resulting in lighter, more efficient designs. However, full order, unsteady time-marching simulations are still prohibitively expensive in an industrial environment. Therefore, different reduced order modelling techniques have been propose to decrease computational cost in many query scenarios while retaining the underlying physics and a high level of accuracy. This paper focuses on an unsteady nonlinear reduced order model based on least squares residual minimization and a comparison to the linearized frequency domain method. While the latter is in line with current industrial practice of sampling aerodynamic forces in the frequency domain, it neglects dynamic nonlinearities which are included in the former approach. Results are presented for an airfoil at transonic flow conditions exhibiting shock induced separation during the airfoil-gust interaction and for the NASA common research model at cruise flight conditions. Essential quantities for the gust loads analysis, such as global coefficients and sectional forces, are evaluated and compared to highlight strengths and weaknesses of both model reduction techniques. Moreover, distributed surface loads, which can be used for a direct sizing of the structural model, are analyzed. Computational cost, split in an offline and an online part, is quantified to demonstrate efficiency gains compared to full-order solutions. * Reseach Scientist, philipp.bekemeyer@dlr.de † Reseach Scientist ‡ Team Leader § Team Leader, AIAA Member Downloaded by BRISTOL UNIVERSITY on July 12, 2018 | http://arc.aiaa.org |

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“…The LFD method was first developed for turbo-machine applications (8,9) and later extended towards external aerodynamics. Published results comprise aerofoil cases, (10,11) isolated wings (12,13) and aircraft configurations. (7,14,15) While the two approaches are well known, the aim of this paper is to analyse these methods at severe flow conditions close to the shock-buffet (16) onset.…”

Section: Introductionmentioning

confidence: 99%

Efficient aerodynamic derivative calculation in three-dimensional transonic flow

Thormann

Timme

2017

Aeronaut. j.

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One key task in computational aeroelasticity is to calculate frequency response functions of aerodynamic coefficients due to structural excitation or external disturbance. Computational fluid dynamics methods are applied for this task at edge-of-envelope flow conditions. Assuming a dynamically linear response around a non-linear steady state, two computationally efficient approaches in time and frequency domain are discussed. A non-periodic, time-domain function can be used, on the one hand, to excite a broad frequency range simultaneously giving the frequency response function in a single non-linear, time-marching simulation. The frequency-domain approach, on the other hand, solves a large but sparse linear system of equations, resulting from the linearisation about the non-linear steady state for each frequency of interest successively. Results are presented for a NACA 0010 aerofoil and a generic civil aircraft configuration in very challenging transonic flow conditions with strong shock-wave/boundary-layer interaction in the pre-buffet regime. Computational cost savings of up to 1 order of magnitude are observed in the time domain for the all-frequencies-at-once approach compared with single-frequency simulations, while an additional order of magnitude is obtained for the frequency-domain method. The paper demonstrates the readiness of computational aeroelasticity tools at edge-of-envelope flow conditions.

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Small Disturbance Navier-Stokes Computations for Low-Aspect-Ratio Wing Pitching Oscillations

Cited by 14 publications

References 18 publications

Neurofuzzy-Model-Based Unsteady Aerodynamic Computations Across Varying Freestream Conditions

Neurofuzzy-Model-Based Unsteady Aerodynamic Computations Across Varying Freestream Conditions

Nonlinear Unsteady Reduced Order Models based on Computational Fluid Dynamics for Gust Loads Predictions

Efficient aerodynamic derivative calculation in three-dimensional transonic flow

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