Aeroelastic and Aerothermoelastic Behavior in Hypersonic Flow
01 Oct 2008-AIAA Journal (American Institute of Aeronautics and Astronautics)-Vol. 46, Iss: 10, pp 2591-2610
TL;DR: In this article, the authors performed a systematic computational study of the hypersonic aeroelastic and aerothermoelastic behavior of a three-dimensional configuration of a low-aspect-ratio wing.
Abstract: The testing of aeroelastically and aerothermoelastically scaled wind-tunnel models in hypersonic flow is not feasible; thus, computational aeroelasticity and aerothermoelasticity are essential to the development of hypersonic vehicles. Several fundamental issues in this area are examined by performing a systematic computational study of the hypersonic aeroelastic and aerothermoelastic behavior of a three-dimensional configuration. Specifically, the flutter boundary of a low-aspect-ratio wing, representative of a fin or control surface on a hypersonic vehicle, is studied over a range of altitudes using third-order piston theory and Euler and Navier-Stokes aerodynamics. The sensitivity of the computational-fluid-dynamics-based aeroelastic analysis to grid resolution and parameters governing temporal accuracy are considered. In general, good agreement at moderate-to-high altitudes was observed for the three aerodynamic models. However, the wing flutters at unrealistic Mach numbers in the absence of aerodynamic heating. Therefore, because aerodynamic heating is an inherent feature of hypersonic flight and the aeroelastic behavior of a vehicle is sensitive to structural variations caused by heating, an aerothermoelastic methodology is developed that incorporates the heat transfer between the fluid and structure based on computational-fluid-dynamics-generated aerodynamic heating. The aerothermoelastic solution procedure is then applied to the low-aspect-ratio wing operating on a representative hypersonic trajectory. In the latter study, the sensitivity of the flutter margin to perturbations in trajectory angle of attack and Mach number is considered. Significant reductions in the flutter boundary of the heated wing are observed. The wing is also found to be susceptible to thermal buckling.
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TL;DR: In this article, it is shown that the body, surface panels, and aerodynamic control surfaces are flexible due to minimum-weight restrictions for hypersonic vehicle configurations, and that these flexible body designs will consist of long, slender lifting body designs.
Abstract: H YPERSONIC flight began in February 1949 when a WAC Corporal rocket was ignited from a U.S.-captured V-2 rocket [1]. In the six decades since this milestone, there have been significant investments in the development of hypersonic vehicle technologies. The NASA X-15 rocket plane in the early 1960s represents early research toward this goal [2,3]. After a lull in activity, the modern era of hypersonic research started in the mid-1980s with the National Aerospace Plane (NASP) program [4], aimed at developing a single-stage-to-orbit reusable launch vehicle (RLV) that used conventional runways. However, it was canceled due mainly to design requirements that exceeded the state of the art [1,5]. A more recent RLV project, the VentureStar program, failed during structural tests, again for lack of the required technology [5]. Despite these unsuccessful programs, the continued need for a low-cost RLV, as well as the desire of the U.S. Air Force (USAF) for unmanned hypersonic vehicles, has reinvigorated hypersonic flight research. An emergence of recent and current research programs [6] demonstrate this renewed interest. Consider, for example, the NASA Hyper-X experimental vehicle program [7], the University of Queensland HyShot program [8], the NASA Fundamental Aeronautics Hypersonics Project [9], the joint U.S. Defense Advanced Research Projects Administration (DARPA)/USAF Force Application andLaunch fromContinentalUnited States (FALCON) program [10], the X-51 Single Engine Demonstrator [11,12], the joint USAF Research Laboratory (AFRL)/Australian Defence Science and Technology Organisation Hypersonic International Flight Research Experimentation project [13], and ongoing basic hypersonic research at the AFRL (e.g., [14–20]). The conditions encountered in hypersonic flows, combined with the need to design hypersonic vehicles, have motivated research in the areas of hypersonic aeroelasticity and aerothermoelasticity. It is evident from Fig. 1 that hypersonic vehicle configurations will consist of long, slender lifting body designs. In general, the body, surface panels, and aerodynamic control surfaces are flexible due to minimum-weight restrictions. Furthermore, as shown in Fig. 2, these
257 citations
Cites background or methods from "Aeroelastic and Aerothermoelastic B..."
...42 Aerothermoelastic flutter margin of the modified low-aspect-ratio wing along a representative hypersonic trajectory [70]....
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...ACATEmethodology that incorporated the heat transfer between the fluid and the structure using CFD-based aerodynamic heating computations was described in [70]....
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...In a similar approach to [70], Gupta et al....
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...36 Flutter envelope of the low-aspect-ratio wing, calculated using third-order PT, Euler, and NS aerodynamics [70]....
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...For both configurations, higher grid resolution near the surface was required at high Mach numbers due to the reduced thickness of the shock layer [70,180]....
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TL;DR: In this paper, the tradeoff between computational cost and accuracy is evaluated for aerothermoelastic analysis based on either quasi-static or time-averaged dynamic fluid-thermal-structural coupling, as well as computational fluid dynamics based reduced-order modeling of the aerodynamic heat flux.
Abstract: The field of aerothermoelasticity plays an important role in the analysis and optimization of airbreathing hypersonic vehicles, impacting the design of the aerodynamic, structural, control, and propulsion systems at both the component and multi-disciplinary levels. This study aims to expand the fundamental understanding of hypersonic aerothermoelasticity by performing systematic investigations into fluid-thermal-structural coupling, and also to develop frameworks, using innovative modeling strategies, for reducing the computational effort associated with aerothermoelastic analysis. Due to the fundamental nature of this work, the analysis is limited to cylindrical bending of a simply-supported, von K arm an panel. Multiple important effects are included in the analysis, namely: 1) arbitrary, nonuniform, in-plane and through-thickness temperature distributions, 2) material property degradation at elevated temperature, and 3) the effect of elastic deformation on aerodynamic heating. It is found that including elastic deformations in the aerodynamic heating computations results in non-uniform heat flux, which produces non-uniform temperature distributions and non-uniform material property degradations. This results in reduced flight time to the onset of flutter and localized regions in which the material temperature limits may be exceeded. Additionally, the trade-off between computational cost and accuracy is evaluated for aerothermoelastic analysis based on either quasi-static or time-averaged dynamic fluid-thermal-structural coupling, as well as computational fluid dynamics based reduced-order modeling of the aerodynamic heat flux. It is determined that these approaches offer the potential for significant improvements in aerothermoelastic modeling in terms of efficiency and/or accuracy.
224 citations
TL;DR: In this paper, various approximations to unsteady aerodynamics are examined for the aero-elastic analysis of a thin double-wedge airfoil in hypersonic flow.
Abstract: DOI: 10.2514/1.C000190 Various approximations to unsteady aerodynamics are examined for the aeroelastic analysis of a thin doublewedge airfoil in hypersonic flow. Flutter boundaries are obtained using classical hypersonic unsteady aerodynamic theories: piston theory, Van Dyke’s second-order theory, Newtonian impact theory, and unsteady shock-expansion theory. The theories are evaluated by comparing the flutter boundaries with those predicted using computational fluid dynamics solutions to the unsteady Navier–Stokes equations. Inaddition, several alternative approaches to the classical approximations are also evaluated: two different viscous approximations based on effective shapes and combined approximate computational approaches that use steady-state computational-fluid-dynamics-based surrogatemodelsinconjunction withpistontheory.Theresultsindicatethat,with theexceptionof first-order piston theory and Newtonian impact theory, the approximate theories yield predictions between 3 and 17% of normalized root-mean-square error and between 7 and 40% of normalized maximum error of the unsteady Navier–Stokes predictions. Furthermore, the demonstrated accuracy of the combined steady-state computational fluid dynamics and piston theory approaches suggest that important nonlinearities in hypersonic flow are primarily due to steadystate effects. This implies that steady-state flow analysis may be an alternative to time-accurate Navier–Stokes solutions for capturing complex flow effects.
111 citations
Cites background or methods from "Aeroelastic and Aerothermoelastic B..."
...The NASA Langley CFL3D code [46,47], used previously by the authors [34,42,48] to conduct studies on the hypersonic aeroelastic behavior of generic reusable launch vehicles and lifting surfaces, is also used in this study for CFD-based aeroelastic analysis....
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...At the other end of the spectrum, advances in computing capabilities have enabled the use of computational fluid dynamics (CFD) modeling of unsteady aerodynamics in hypersonic aeroelastic studies [34,35]....
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...This apparent thickness influences both the surface pressure distribution and the vehicle aeroelastic stability [31,32,34]....
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...However, such approaches remain impractical for detailed aerothermoelastic analysis over an extended trajectory [34,36,37]....
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...This grid configuration and density was selected based on a mesh refinement study in [34] that demonstrated convergence of lift and moment coefficients to within 5%and average y values for thefirst grid point off the surface to less than 2....
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TL;DR: In this article, an aerothermoelastic framework with reduced-order aerothermal, heat transfer, and structural dynamic models for time-domain simulation of hypersonic vehicles is presented.
Abstract: Hypersonic vehicle control system design and simulation require models that contain a low number of states. Modeling of hypersonic vehicles is complicated due to complex interactions between aerodynamic heating, heat transfer, structural dynamics, and aerodynamics. Although there exist techniques for analyzing the effects of each of the various disciplines, thesemethods often require solution of large systems of equations, which is infeasible within a control design and evaluation environment. This work presents an aerothermoelastic framework with reducedorder aerothermal, heat transfer, and structural dynamicmodels for time-domain simulation of hypersonic vehicles. Details of the reduced-order models are given, and a representative hypersonic vehicle control surface used for the study is described. Themethodology is applied to a representative structure to provide insight into the importance of aerothermoelastic effects on vehicle performance. The effect of aerothermoelasticity on total lift and drag is found to result in up to an 8% change in lift and a 21% change in drag with respect to a rigid control surface for the four trajectories considered. An iterative routine is used to determine the angle of attack needed to match the lift of the deformed control surface to that of a rigid one at successive time instants.Application of the routine todifferent cruise trajectories shows a maximum departure from the initial angle of attack of 8%.
99 citations
Cites background or methods from "Aeroelastic and Aerothermoelastic B..."
...Recent research on aerothermoelastic stability of a HSV control surface used computational fluid dynamics (CFD) to compute the aerodynamic heating alongwith finite element thermal and structural models to assess its behavior in hypersonic flow [17]....
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...Note that cells are clustered near the surface, leading edge, and midchord, since these locations correspond to maximum flow gradients [17]....
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...While [17] reduced the order of the equations of motion by applying a truncated set of free vibration mode shapes, an eigenvalue solution was still computed at each desired point in time to update themode shapes....
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TL;DR: This study examines two model reduction strategies with the goal to enable the use of computational fluid dynamics within a long time-record, dynamic, aerothermoelastic analysis.
Abstract: A primary challenge for aerothermoelastic analysis in hypersonic flow is accurate and efficient computation of unsteady aerothermodynamic loads. This study examines two model reduction strategies with the goal to enable the use of computational fluid dynamics within a long time-record, dynamic, aerothermoelastic analysis. One approach seeks to exploit the quasi-steady nature of the flow by using steady-state computational fluid dynamics to capture primary flow features, and simple analytical approximations to account for unsteady effects. The second approach seeks to minimize the computational cost of steady-state computational fluid dynamics flow analysis using either kriging or proper orthogonal decomposition-based modeling techniques. These model reduction strategies are assessed, both individually and combined, in the context of a three-dimensional hypersonic control surface. Results computed over a wide range of operating conditions and reduced frequencies indicate that when combined, the considered approaches yield an aerothermodynamic model that is tractable within a dynamic aerothermoelastic analysis, and generally has less than 5% maximum error relative to computational fluid dynamics.
91 citations
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Abstract: Some Preliminary Thoughts * Part I: Inviscid Hypersonic Flow * Hypersonic Shock and Expansion-Wave Relations * Local Surface Inclination Methods * Hypersonic Inviscid Flowfields: Approximate Methods * Hypersonic Inviscid Flowfields: Exact Methods * Part II: Viscous Hypersonic Flow * Viscous Flow: Basic Aspects, Boundary Layer Results, and Aerodynamic Heating * Hypersonic Viscous Interactions * Computational Fluid Dynamic Solutions of Hypersonic Viscous Flows * Part III: High-Temperature Gas Dynamics * High-Temperature Gas Dynamics: Some Introductory Considerations * Some Aspects of the Thermodynamics of Chemically Reacting Gases (Classical Physical Chemistry) * Elements of Statistical Thermodynamics * Elements of Kinetic Theory * Chemical Vibrational Nonequilibrium * Inviscid High-Temperature Equilibrium Flows * Inviscid High-Temperature Nonequilibrium Flows * Kinetic Theory Revisited: Transport Properties in High-Temperature Gases * Viscous High-Temperature Flows * Introduction to Radiative Gas Dynamics.
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"Aeroelastic and Aerothermoelastic B..." refers methods in this paper
...Therefore, several different approaches have emerged as alternatives to partial regridding in transient aeroelastic computations, among them being dynamic meshes [39], the space–time formulation [40–42], the arbitrary/mixed Eulerian–Lagrangian formulation [43,44], the multiple-field formulation [45,46], the transpiration method [7,47], the exponential-decay/transfinite-interpolation (TFI) method [48,49], the modified spring analogy [33], and the finite macroelement method [49,50]....
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TL;DR: Current Practice Block-Structured Grids Unstructuring Grids Cartesian Grids Overset Grids Hybrid Grids Adaptive and Moving Grids System Implementation Block Structured GrIDS Unstructured Grid System Implementation User Interfaces Grid Automation CAD Interfaces grid Visualization MDO Coupling Grid Generation Systems Algebraic Generation Elliptic Generation Hyperbolic Generation Delaunay Tetrahedral Generation Advancing-Front unstructured Generation Hexahedral Generation.
Abstract: Current Practice Block-Structured Grids Unstructured Grids Cartesian Grids Overset Grids Hybrid Grids Adaptive and Moving Grids System Implementation Block Structured Grids Unstructured Grids Cartesian Grids Overset Grids Hybrid Grids User Interfaces Grid Automation CAD Interfaces Grid Visualization MDO Coupling Grid Generation Systems Algebraic Generation Elliptic Generation Hyperbolic Generation Delaunay Tetrahedral Generation Advancing-Front Unstructured Generation Hexahedral Generation Structured Surface Grids Unstructured Surface Grids Supporting Technology Available Codes
909 citations
"Aeroelastic and Aerothermoelastic B..." refers methods in this paper
...Intervening mesh points on block faces are updated using TFI, a scheme [51] that efficiently maps grid displacements from one block face to another using polynomial functions....
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TL;DR: In this paper, a new strategy based on the stabilized space-time finite element formulation is proposed for computations involving moving boundaries and interfaces, where the deformation of the spatial domain with respect to time is taken into account automatically.
Abstract: A new strategy based on the stabilized space-time finite element formulation is proposed for computations involving moving boundaries and interfaces. In the deforming-spatial-domain/space-time (DSD/ST) procedure the variational formulation of a problem is written over its space-time domain, and therefore the deformation of the spatial domain with respect to time is taken into account automatically. Because the space-time mesh is generated over the space-time domain of the problem, within each time step, the boundary (or interface) nodes move with the boundary (or interface). Whether the motion of the boundary is specified or not, the strategy is nearly the same. If the motion of the boundary is unknown, then the boundary nodes move as defined by the other unknowns at the boundary (such as the velocity or the displacement). At the end of each time step a new spatial mesh covers the new spatial domain. For computational feasibility, the finite element interpolation functions are chosen to be discontinuous in time, and the fully discretized equations are solved one space-time slab at a time.
833 citations
TL;DR: In this article, two algorithms for the solution of the time-dependent Euler equations are presented for unsteady aerodynamic analysis of oscillating airfoils for use on an unstructured grid made up of triangles.
Abstract: Two algorithms for the solution of the time-dependent Euler equations are presented for unsteady aerodynamic analysis of oscillating airfoils. Both algorithms were developed for use on an unstructured grid made up of triangles. The first flow solver involves a Runge-Kutta time-stepping scheme with a finite-volume spatial discretization that reduces to central differencing on a rectangular mesh. The second flow solver involves a modified Euler time-integration scheme with an upwind-biased spatial discretization based on the flux-vector splitting of Van Leer. The paper presents descriptions of the Euler solvers and dynamic mesh algorithm along with results which assess the capability.
783 citations
"Aeroelastic and Aerothermoelastic B..." refers methods in this paper
...Therefore, several different approaches have emerged as alternatives to partial regridding in transient aeroelastic computations, among them being dynamic meshes [39], the space–time formulation [40–42], the arbitrary/mixed Eulerian–Lagrangian formulation [43,44], the multiple-field formulation [45,46], the transpiration method [7,47], the exponential-decay/transfinite-interpolation (TFI) method [48,49], the modified spring analogy [33], and the finite macroelement method [49,50]....
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...This scheme is a modification of the spring analogy [39] by using axial spring stiffness....
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