Computational Investigation into the Use of Response Functions for Aerodynamic-Load Modeling

Ghoreyshi, Mehdi; Jirasek, Adam; Cummings, Russell M.

doi:10.2514/1.j051428

Cited by 69 publications

(28 citation statements)

References 49 publications

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“…The use of flight dynamic databases through which a configuration is "flown" has been developed in aircraft manoeuvre modelling, and for complex non-linear manoeuvres requires the addition of dynamic derivatives [60] and, as a next step, Reduced-Order Methods (e.g. [61]). These have proved reasonable for linear coefficients, but less accurate for non-linear rolling and yawing moments.…”

Section: Earlier Workmentioning

confidence: 99%

Theoretical treatment of fluid flow for accelerating bodies

Gledhill¹,

Roohani

Forsberg

et al. 2016

Theor. Comput. Fluid Dyn.

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Most computational fluid dynamics simulations are, at present, performed in a body-fixed frame, for aeronautical purposes. With the advent of sharp manoeuvre, which may lead to transient effects originating in the acceleration of the centre of mass, there is a need to have a consistent formulation of the Navier–Stokes equations in an arbitrarily moving frame. These expressions should be in a form that allows terms to be transformed between non-inertial and inertial frames and includes gravity, viscous terms, and linear and angular acceleration. Since no effects of body acceleration appear in the inertial frame Navier–Stokes equations themselves, but only in their boundary conditions, it is useful to investigate acceleration source terms in the non-inertial frame. In this paper, a derivation of the energy equation is provided in addition to the continuity and momentum equations previously published. Relevant dimensionless constants are derived which can be used to obtain an indication of the relative significance of acceleration effects. The necessity for using computational fluid dynamics to capture nonlinear effects remains, and various implementation schemes for accelerating bodies are discussed. This theoretical treatment is intended to provide a foundation for interpretation of aerodynamic effects observed in manoeuvre, particularly for accelerating missiles.

Funding agencies: DRDB [KT466921, KT528944, KT470887]

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Section: Earlier Workmentioning

confidence: 99%

Theoretical treatment of fluid flow for accelerating bodies

Gledhill¹,

Roohani

Forsberg

et al. 2016

Theor. Comput. Fluid Dyn.

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Funding agencies: DRDB [KT466921, KT528944, KT470887]

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“…8a, the pitch-moment responses have a negative peak at t 0 followed by an increasing trend. As the steady flow around the vehicle is disturbed by the grid motion, a compression wave and an expansion wave are formed on the lower and upper surface of the vehicle that cause a sharp negative pitchmoment peak in the responses [32]. As the response time progresses, the waves begin to move away from the vehicle, and the pitchmoment responses start to increase and then asymptotically reach the steady-state values.…”

Section: Resultsmentioning

confidence: 99%

“…This approach allows the uncoupling of effects of angle of attack and pitch rate for the indicial functions. Cobalt uses an arbitrary Lagrangian-Eulerian formulation and hence allows all translational and rotational degrees of freedom [32]. The motion is specified from an input file that has the location of a reference point on the aircraft at each time step.…”

Section: G System Identificationmentioning

confidence: 99%

“…Singh and Baeder [31] used a surface transpiration approach to directly calculate the angle-of-attack indicial response using CFD. Ghoreyshi et al [32] also described an approach based on a grid-motion technique for CFD-type calculation of linear and nonlinear indicial functions with respect to angle of attack and pitch rate. Ghoreyshi and Cummings [25] later used this approach to generate longitudinal and lateral indicial functions for a generic unmanned combat air vehicle and used these functions for predicting the aerodynamic responses to aircraft six-degree-offreedom maneuvers.…”

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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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“…For three-dimensional flow, all these fundamental functions [44][45][46][47] are modified so to include the unsteady downwash of the trailed wing-tip vortices [48][49][50][51][52] and the results are then approximated for computational convenience [53][54][55][56][57][58][59][60][61][62][63][64][65][66]; Appendix B reports the applications to elliptical and trapezoidal wings [20][21]. Due to rigorous analytical continuation [41], with s the Laplace variable, a rational approximation [22,67] is suitably adopted for the equivalent of Theodorsen function in the complex reduced frequency p domain, namely:…”

Section: Added Aerodynamic Statesmentioning

confidence: 99%