A hybrid finite-volume-rom approach to non-linear aerospace fluid-structure interaction modelling. (original) (raw)
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Hybrid Finite-Volume Reduced-Order Model Method for Nonlinear Aeroelastic Modeling.
A fully coupled partitioned fluid–structure interaction technology is developed for transonic aeroelastic structures undergoing nonlinear displacements. The Euler equations, written in an arbitrary Lagrangian–Eulerian coordinate frame, describe the fluid domain, whereas the structure is represented by a quadratic modal reduced-order model. A Runge–Kutta dual time-stepping method is employed for the fluid solver, where three upwind schemes are considered, viz., Advection Upwind Splitting Method plus-up, Harten-Lax-van Leer with Contact, and Roe schemes. The Harten-Lax-van Leer with Contact implementation is found to offer a superior balance between efficiency and robustness. The developed fluid–structure interaction technology is applied to modeling transonic flutter, and the quadratic reduced-order model is demonstrated to offer dramatic improvements in accuracy over the more conventional linear method.
Proceedings of the 3rd South-East European Conference on Computational Mechanics – SEECCM III, 2013
We investigate model reduction techniques through computational aeroelastic analyses of the HIRENASD and S 4 T wings. The aim of the present work is to construct accurate and computationally efficient reduced order models for high-fidelity aeroelastic computations. Firstly, the aeroelastic analyses of the specified wings are performed by high-fidelity structural and aerodynamic models to substantiate the fluid-structure interaction. Concerning high amount of computational time required to perform such high-fidelity fluid-structure interaction analyses, the model orders are reduced by introducing relevant reduction techniques such as Polynomial Chaos Expansion and Proper Orthogonal Decomposition. The final aeroelastic analyses performed on these reduced models agree well with the initial high-fidelity computational analyses.
Adaptive reduced-order modeling for non-linear fluid–structure interaction
Computers & Fluids
We present an adaptive reduced-order model for the efficient time-resolved simulation of fluid-structure interaction problems with complex and non-linear deformations. The model is based on repeated linearizations of the structural balance equations. Upon each linearization step, the number of unknowns is strongly decreased by using modal reduction, which leads to a substantial gain in computational efficiency. Through adaptive re-calibration and truncation augmentation whenever a non-dimensional deformation threshold is exceeded, we ensure that the reduced modal basis maintains arbitrary accuracy for small and large deformations. Our novel model is embedded into a partitioned, loosely coupled finite volume-finite element framework, in which the structural interface motion within the Eulerian fluid solver is accounted for by a conservative cut-element immersed-boundary method. Applications to the aeroelastic instability of a flat plate at supersonic speeds, to an elastic panel placed within a shock tube, and to the shock induced buckling of an inflated thin semi-sphere demonstrate the efficiency and accuracy of the method.
Fluid–structure interaction for aeroelastic applications
Progress in Aerospace Sciences, 2004
The interaction between a flexible structure and the surrounding fluid gives rise to a variety of phenomena with applications in many areas, such as, stability analysis of airplane wings, turbomachinery design, design of bridges, and the flow of blood through arteries. Studying these phenomena requires modeling of both fluid and structure. Many approaches in computational aeroelasticity seek to synthesize independent computational approaches for the aerodynamic and the structural dynamic subsystems. This strategy is known to be fraught with complications associated with the interaction between the two simulation modules. The task is to choosing the appropriate models for fluid and structure based on the application, and to develop an efficient interface to couple the two models. In the present article, we review the recent advancements in the field of fluid-structure interaction, with specific attention to aeroelastic applications. One of the key aspects to developing a robust coupled aeroelastic model is the presence of an efficient moving grid technique to account for structural deformations. Several such techniques are reviewed in this paper. Also, the time scales associated with fluid-structure interaction problems can be very different; hence, appropriate time stepping strategies and/or sub-cycling procedures within the individual field need to be devised. The flutter predictions performed on an AGARD 445.6 wing at different Mach numbers are selected to highlight the stateof-the-art computational and modeling issues. r
Recent Advances in Reduced-Order Modeling and Application to Nonlinear Computational Aeroelasticity
& Proceedings 저널· 프로시딩즈| 기술보고서| 해외 …, 2008
Reduced-order models (ROMs) are usually thought of as computationally inexpensive mathematical representations that offer the potential for near real-time analysis. Indeed, most ROMs can operate in near real-time. However, their construction can be computationally intensive as it requires accumulating a large number of system responses to input excitations. Furthermore, ROMs usually lack robustness with respect to parameter changes and therefore must often be rebuilt for each parameter variation. Together, these two issues underline the need for a fast and robust method for adapting pre-computed ROMs to new sets of physical or modeling parameters. To this effect, this paper reports on recent advances in this topic. In particular, it describes a recently developed interpolation method based on the Grassmann manifold and its tangent space at a point that is applicable to structural, aerodynamic, aeroelastic and many other ROMs based on projection schemes. This method is illustrated here with the adaptation of CFD-based aeroelastic ROMs of complete fighter configurations to new values of the free-stream Mach number. Good correlations with results obtained from direct ROM reconstruction and high-fidelity linear and nonlinear simulations are reported, thereby highlighting the potential of the described ROM adaptation method for near real-time aeroelastic predictions using pre-computed ROM databases. example, in the transonic regime. This cost is such that CFD-based nonlinear aeroelastic codes are applied nowadays to the analysis of a few, carefully chosen configurations, rather than routine analysis.
Assessment and development of a ROM for linearized aeroelastic analyses of aerospace vehicles
CEAS Aeronautical Journal, 2017
In the present work, a reduced order model (ROM) for aeroelastic analysis linearized around non-linear steady solutions has been assessed and implemented to perform high-fidelity predictions, in particular for transonic flow. The ROM has been specifically adopted for identifying the unsteady aerodynamics by means of a modalbased approach. This goal has been achieved by performing a series of prescribed modal-transient boundary conditions on a Euler-based computational fluid-dynamics code and then post-processing the input/output data in the frequency domain. A fast and efficient morphing code based on the use of radial basis functions has been introduced at this phase of the procedure to reach a wide range of applicability for significant cases with complex geometries as in the case of aeronautical and space vehicles. Flutter boundaries have been investigated by capturing the so-called transonic dip phenomenon, mainly due to compressibility and evidenced in the literature also by wind tunnel tests. Comparisons of the present results with linear lower fidelity approaches, based on potential flows, have demonstrated the capabilities of the proposed ROM. Finally, in order to show the general-purpose applicability of the proposed approach, the method has been applied to the aeroelastic analysis of a launch vehicle. For this application no commercial codes for linear aeroelastic analysis are available for comparisons. Keywords ROM Á Linearized aeroelasticity Á Flutter Á Mesh morphing Á RBF Á Experimental results Á Launch vehicle & F. Mastroddi
Numerical simulation of 3-D wing flutter with fully coupled fluid–structural interaction
Computers & Fluids, 2007
A numerical methodology coupling Navier-Stokes equations and structural modal equations for predicting 3-D transonic wing flutter is developed in this paper. A dual-time step implicit unfactored Gauss-Seidel iteration with the Roe scheme is employed for the flow solver. A modal approach is used for the structural response. The flow and structural solvers are fully coupled via successive iterations within each physical time step. The mesh-deformation strategy is described. The accuracy of the modal approach is validated with ANSYS. The results indicate that the first five modes are sufficient to accurately model the wing-structure response for the studied case of this paper. The computed flutter boundary of AGARD wing 445.6 at free stream Mach numbers ranging from 0.499 to 1.141 agrees well with the experiment.
Reduced-order fluid/structure modeling of a complete aircraft configuration
Computer Methods in Applied Mechanics and Engineering, 2006
... the exclusive use of linear aerodynamic theories for predicting the unsteady aerodynamic forces. ... Because of this computational cost, the potential of CFD-based nonlinear aeroelastic codes ... possible however to address this limitation with the use of reduced-order models (ROMs ...
Stable and accurate loosely-coupled scheme for unsteady fluid-structure interaction
AIAA Paper, 2007
This paper presents a new loosely-coupled partitioned procedure for modeling fluid-structure interaction. The procedure relies on a higher-order Combined Interface Boundary Condition (CIBC) treatment for improved accuracy and stability of fluid-structure coupling. Traditionally, continuity of velocity and momentum flux along interfaces are satisfied through algebraic interface conditions applied in a sequential fashion, which is often referred to staggered computation. In existing staggered procedures, the interface conditions undermine stability and accuracy of coupled fluid-structure simulations. By utilizing the CIBC technique on the velocity and momentum flux boundary conditions, a staggered coupling procedure can be constructed with similar order of accuracy and stability of standalone computations. Introduced correction terms for velocity and momentum flux transfer can be explicitly added to the standard staggered time-stepping stencils so that the discretization is well-defined across the deformable interface. The new formulation involves a coupling parameter, which has an interval of well-performing values for both classical 1D closed-and open-elastic piston problems. The technique is also demonstrated in 2D in conjunction with the common refinement method for subsonic flow over a thin-shell structure.
Static/Dynamic Correction Approach for Reduced-Order Modeling of Unsteady Aerodynamics
Journal of Aircraft, 2006
Presented is a newly devised static/dynamic correction approach for eigenvector expansion based reduced-order modeling (ROM). When compared to the fundamental Ritz ROM formulation, along with the static and multiple static correction ROM approaches, the technique is demonstrated to have much better performance in modeling unsteady linearized frequency-domain aerodynamics in regions of the complex frequency plane near the imaginary axis, and up to a prescribed frequency of interest. As with the static and multiple static correction approaches, the method requires a directly computed solution at zero frequency. The method then requires one additional direct solution to be computed at some nonzero frequency, which typically is the maximum frequency of interest. When compared to the multiple static corrections method, the method circumvents the necessity of having to determine each of the multiple static corrections, which require a solution to an alternate set of equations that must be formulated and which can be costly to solve for large systems. We also consider the feasibility of using a proper orthogonal decomposition (POD) to determine approximations for the least damped fluid-dynamic eigenvectors. We demonstrate that in certain situations these approximate eigenvectors can be used in conjunction with the static/dynamic correction ROM approach to achieve an improvement in performance over the recently devised POD/ROM method where the POD shapes alone are used as ROM shape vectors. Finally, we illustrate how the method can be coupled with a structural model to compute the Mach-number flutter speed trend for a large computational-fluid-dynamics model of a three-dimensional transonic wing configuration.