Simulation of Aircraft Manoeuvres based on Computational Fluid Dynamics

Progress in Aerospace Sciences

Jirasek

Cummings

2014

Self Cite

118

, "Reduced order unsteady aerodynamic modeling for stability and control analysis using computational fluid dynamics" (2014 Contents ABSTRACTRecent advances and challenges in the generation of reduced order aerodynamic models using computational fluid dynamics are presented. The models reviewed are those that can be used for aircraft stability and control analysis and include linear and nonlinear indicial response methods, Volterra theory, radial basis functions, and a surrogate-based recurrence framework. The challenges associated with identification of unknowns for each of the reduced order methods are addressed. A range of test cases, from airfoils to full aircraft, have been used to evaluate and validate the reduced order methods. The motions have different amplitudes and reduced frequencies and could start from different flight conditions including those in the transonic speed range. Overall, these reduced order models help to produce accurate predictions for a wide range of motions, but with the advantage that model predictions require orders of magnitude less time to evaluate once the model is created.Published by Elsevier Ltd.

Section: The Need For Reduced Order Unsteady Aerodynamics Modelingmentioning

confidence: 99%

Reduced order unsteady aerodynamic modeling for stability and control analysis using computational fluid dynamics

Progress in Aerospace Sciences

Jirasek

Cummings

2014

Self Cite

118

“…A number of methods for treating control surfaces are available that eliminate the need to regenerate grids. Ghoreyshi et al, 25 for example, used mode shapes for the control surface deflections. Each mode shape specifies the displacement of the grid points on the aircraft surface for a particular control surface.…”

Section: Introductionmentioning

confidence: 99%

From Spreadsheets to Simulation-Based Aircraft Conceptual Design

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

Jirasek

Brandt

et al. 2012

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An automated, simulation-based aircraft design process allows for the prediction of unanticipated problems early in the design stage, leading to reduced turn-around time and development cost. Having reliable, and affordable (fast) design tools is crucial to achieving this level of automation in the design process. An example of this is illustrated for a jet trainer aircraft using two aircraft design codes: Jet Designer and CEASIOM which includes Digital DATCOM, a Vortex lattice method, and an Euler flow solver. A set of aerodynamic methods with different degrees of fidelity and computational expense is considered, with the limitations of each method provided. In particular, this paper examines the challenges that CFD-based aircraft design poses to a designer, including: a) the cost of generation of large data tables, b) the automated handling of geometry, c) treating control surface deflections, d) and calculation of dynamic derivatives using CFD. A Kriging-based sampling approach was used for generating aerodynamic tables with a reasonable computational cost compared with a brute-force approach. For Euler calculations, an automated CAD and mesh generation approach from a geometry description was used. It is demonstrated that application of Euler solutions to low fidelity aircraft geometry shows the expected design trends. Also, results show that the wave drag at transonic speeds can be predicted with Euler equations, but not with Vortex lattice or Digital DATCOM. The treatment of control surface deflections was also investigated for the Vortex lattice solver and the Euler code. A transpiration boundary condition was used in the Euler code to model the flap surface movements, although this approach is limited for large deflections. The calculated aero tables form each aero source were used next to study the vehicle flying qualities. Results presented demonstrate the validity and feasibility of the simulation-based approach for aircraft conceptual design. Nomenclaturelift curve slope, 1/rad C Lq lift derivative with respect to normalized pitch rate, 1/rad C m pitching moment coefficient, m/q ∞ Sc C mα pitching moment slope, 1/rad C mq pitching moment derivative with respect to normalized pitch rate, 1/rad C mδe pitching moment derivative with respect to elevator deflection, 1/rad C Y side-force coefficient, Y /q ∞ S *

“…(6), and the function Φ maps the inputs to the outputs. The terms m and n represent the number of previous values of the external inputs and outputs, respectively, influencing the output at the current time instant.…”

Section: Surrogate-based Modeling Of Indicial Functionsmentioning

confidence: 99%

Transonic Aerodynamic Loads Modeling of X-31 Aircraft

30th AIAA Applied Aerodynamics Conference

Post

Cummings

et al. 2012

Self Cite

The generation of reduced order models for computing the unsteady and nonlinear aerodynamic loads on the X-31 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). One of the biggest challenges in creating these reduced order modeling techniques is accurate identification of unknowns. A large number of step function calculation is required for any combination of angle of attack and free-stream Mach number. A method to efficiently reduce the number of step function calculations is proposed. This method uses a time-dependent surrogate model to fit the relationship between flight conditions (Mach number and angle of attack) and step functions calculated from a limited number of simulations (samples). Each sample itself is directly calculated from unsteady Reynolds-Averaged Navier-Stokes simulations starting from an initial steady-state condition with a prescribed grid motion. An indirect method is proposed to estimate the nonlinear Volterra kernels from time-accurate computational fluid dynamic simulations of different training maneuvers. These maneuvering simulations were also used to estimate the unknown parameters in a model based on Radial Basis functions. A Design of Experiment method was used to generate several pitching motions at different amplitudes and free-stream Mach numbers. The model based on a surrogate-based recurrence framework then approximates the aerodynamic responses induced by pitching motions at new flight conditions. Results are reported for the X-31 configuration with a sharp leading-edge geometry, including canard/wing vortices. The validity of models studied was assessed by comparison of the model outputs with time-accurate computational fluid dynamic 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 developed time-dependent surrogate approach, helped to produce accurate predictions for a wide range of motions in the transonic speed range within a few seconds.