Development of a nonlinear indicial model using response functions generated by a neural network

Reisenthel, Patrick

doi:10.2514/6.1997-337

Cited by 23 publications

(20 citation statements)

References 12 publications

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“…The indicial response functions are used as a fundamental approach to represent the unsteady aerodynamic loads. The mathematical models are detailed by Tobak et al [14,15], Reisenthel [23], and Reisenthel and Bettencourt [24]. The pitch moment is only considered in this paper because it is the more-difficult parameter to predict.…”

Section: Reduced-order Models Based On Indicial Functionsmentioning

confidence: 99%

mentioning

confidence: 99%

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Transonic Aerodynamic Load Modeling of X-31 Aircraft Pitching Motions

Ghoreyshi¹,

Cummings²,

Ronch³

et al. 2013

AIAA Journal

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The generation of reduced-order models for computing the unsteady and nonlinear aerodynamic loads on an aircraft from pitching motions in the transonic speed range is described. The models considered are based on Duhamel's superposition integral using indicial (step) response functions, Volterra theory using nonlinear kernels, radial basis functions, and a surrogate-based recurrence framework, both using time-history simulations of a training maneuver(s). Results are reported for the X-31 configuration with a sharp leading-edge cranked delta wing geometry, including canard/wing vortex interactions. The validity of the various models studied was assessed by comparison of the model outputs with time-accurate computational-fluid-dynamics simulations of new maneuvers. Overall, the reduced-order models were found to produce accurate results, although a nonlinear model based on indicial functions yielded the best accuracy among all models. This model, along with a time-dependent surrogate approach, helped to produce accurate predictions for a wide range of motions in the transonic speed range. = regression coefficients ε = kriging random process μ = air viscosity; kriging mean value ρ = density, kg∕m 3 σ 2 = covariance τ ij = viscous stress tensor components, Pa Φ i X = radial basis functions ω = circular frequency, rad∕s

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Section: Reduced-order Models Based On Indicial Functionsmentioning

confidence: 99%

mentioning

confidence: 99%

Transonic Aerodynamic Load Modeling of X-31 Aircraft Pitching Motions

Ghoreyshi¹,

Cummings²,

Ronch³

et al. 2013

AIAA Journal

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“…Assuming that the indicial functions are known, the aerodynamic forces and moments induced in any maneuver can be estimated by using the well-known Duhamel superposition integral [36]. Tobak et al [62,61] and Reisenthel et al [50,51] detailed the superposition process for the modeling of unsteady lift and pitch moment from angle of attack and pitch rate indicial functions. If the time responses in lift due to the step changes in angle of attack, α, and angular velocity, q, are known, then the total produced lift at time t can be obtained as: (14) where C L0 denotes the zero-angle of attack lift coefficient and is found from static calculations; M is the free-stream Mach number; C Lα and C Lq are lift indicial functions.…”

Section: Indicial Functionsmentioning

confidence: 99%

Challenges in the aerodynamics modeling of an oscillating and translating airfoil at large incidence angles

Ghoreyshi

Cummings

2013

Aerospace Science and Technology

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The challenges in the modeling of the unsteady lift of a two-dimensional NACA 0012 airfoil oscillating and translating at large incidence angles are investigated in this paper. Forced oscillation motions with two reduced frequency values of 0.1 and 1.0 were used. The CFD results show that a hysteresis loop was developed in the lift variation with angle of attack; shapes of the loops change significantly with reduced frequency value. A dynamic stall vortex was identified in the pitching and plunging motions with k = 0.1.This vortex delays the onset of flow separation over the upper surface to a higher incidence than would occur in steady conditions. The unsteady lift of the very fast motion is enhanced significantly due to the formation of a compression wave on the lower surface and an expansion wave on the upper surface. The results show clear limitations of unsteady aerodynamic theories for modeling motions at high incidences. Also, the CFD solution of indicial functions show a large oscillation at angles of attack beyond the stall angle, but the predictions of a model based on Radial Basis Function matches CFD values quite well.

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“…There range [9]. The indicial and critical-state responses are, however, differences in the quadrature method contained in the database are as follows:…”

Section: Csmentioning

confidence: 99%

A nonlinear indicial prediction tool for unsteady aerodynamic modeling

Reisenthel

Bettencourt

Mayatt³

et al. 1998

23rd Atmospheric Flight Mechanics Conference

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The present paper describes a new tool kit which can be used to model the time-dependent response of nonlinear systems. The Indicial Prediction System (IPS) applies nonlinear indicial theory to solve complex unsteady problems, such as those associated with nonlinear aerodynamic phenomena during maneuver of aircraft. The functionality of this system and its capabilities are described through numerous examples. An important demonstration of the method is its application to the prediction of the aerodynamic loads on a 65-degree delta wing undergoing forced body-axis rolling motions at high angles of attack.

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Development of a nonlinear indicial model using response functions generated by a neural network

Cited by 23 publications

References 12 publications

Transonic Aerodynamic Load Modeling of X-31 Aircraft Pitching Motions

Transonic Aerodynamic Load Modeling of X-31 Aircraft Pitching Motions

Challenges in the aerodynamics modeling of an oscillating and translating airfoil at large incidence angles

A nonlinear indicial prediction tool for unsteady aerodynamic modeling

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