Flutter simulations of a T‐tail configuration using non‐linear aerodynamics

Arizono, Hitoshi; Kheirandish, Hamid Reza; Nakamichi, Jiro

doi:10.1002/nme.2047

Cited by 7 publications

(5 citation statements)

References 15 publications

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“…In these cases, the only reliable descriptions of the fluid flow behavior are those capable of capturing shock waves with the correct positioning, such as those based on full potential, Euler or Navier-Stokes equations, since the nature of the aerodynamic equations becomes intrinsically nonlinear. A numerical investigation of transonic flow on the T-tail flutter boundaries for a wind tunnel model has been already presented by Arizono et al (2007). However, several authors (e.g.…”

Section: Introductionmentioning

confidence: 98%

Aircraft T-tail flutter predictions using computational fluid dynamics

Attorni

Cavagna

Quaranta

2011

Journal of Fluids and Structures

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Section: Introductionmentioning

confidence: 98%

Aircraft T-tail flutter predictions using computational fluid dynamics

Attorni

Cavagna

Quaranta

2011

Journal of Fluids and Structures

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“…Alternatively, unsteady CFD methods may be used to inherently capture the aerodynamic forces to their full extent. Within the scope of the development of a tool for the estimation of flutter boundaries at transonic flight speeds based on linear structure and nonlinear, inviscid aerodynamics, numerical studies and wind tunnel experiments are compared in [9]. The wind tunnel model used for the verification, however, features a very stiff Vertical Tail Plane (VTP) and, therefore, does not show the common T-tail flutter phenomenon, usually consisting of VTP out-of-plane bending and torsion.…”

Section: Introductionmentioning

confidence: 99%

Influence of Fluid Viscosity and Compressibility on Nonlinearities in Generalized Aerodynamic Forces for T-Tail Flutter

Schäfer

2022

Aerospace

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The numerical assessment of T-tail flutter requires a nonlinear description of the structural deformations when the unsteady aerodynamic forces comprise terms from lifting surface roll motion. For linear flutter, a linear deformation description of the vertical tail plane (VTP) out-of-plane bending results in a spurious stiffening proportional to the steady lift forces, which is corrected by incorporating second-order deformation terms in the equations of motion. While the effect of these nonlinear deformation components on the stiffness of the VTP out-of-plane bending mode shape is known from the literature, their impact on the aerodynamic coupling terms involved in T-tail flutter has not been studied so far, especially regarding amplitude-dependent characteristics. This term affects numerical results targeting common flutter analysis, as well as the study of amplitude-dependent dynamic aeroelastic stability phenomena, e.g., Limit Cycle Oscillations (LCOs). As LCOs might occur below the linear flutter boundary, fundamental knowledge about the structural and aerodynamic nonlinearities occurring in the dynamical system is essential. This paper gives an insight into the aerodynamic nonlinearities for representative structural deformations usually encountered in T-tail flutter mechanisms using a CFD approach in the time domain. It further outlines the impact of geometrically nonlinear deformations on the aerodynamic nonlinearities. For this, the horizontal tail plane (HTP) is considered in isolated form to exclude aerodynamic interference effects from the studies and subjected to rigid body roll and yaw motion as an approximation to the structural mode shapes. The complexity of the aerodynamics is increased successively from subsonic inviscid flow to transonic viscous flow. At a subsonic Mach number, a distinct aerodynamic nonlinearity in stiffness and damping in the aerodynamic coupling term HTP roll on yaw is shown. Geometric nonlinearities result in an almost entire cancellation of the stiffness nonlinearity and an increase in damping nonlinearity. The viscous forces result in a stiffness offset with respect to the inviscid results, but do not alter the observed nonlinearities, as well as the impact of geometric nonlinearities. At a transonic Mach number, the aerodynamic stiffness nonlinearity is amplified further and the damping nonlinearity is reduced considerably. Here, the geometrically nonlinear motion description reduces the aerodynamic stiffness nonlinearity as well, but does not cancel it.

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“…For VTP torsion, the HTP yaws, which results in asymmetrical aerodynamic span loading and a corresponding rolling moment. An assessment of T-tail flutter stability therefore requires correction of DLM unsteady aerodynamics [1][2][3], the use of enhanced DLM algorithms [4], UVLM [5], or CFD approaches [6][7][8][9][10]. Van Zyl pointed out, however, that the consideration of the additional aerodynamic terms alone can actually reduce the flutter velocity prediction accuracy when a modal approach is applied with a linear displacement model.…”

Section: Introductionmentioning

confidence: 99%

T-tail flutter simulations with regard to quadratic mode shape components

Schäfer

2021

CEAS Aeronaut J

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It is known that the dynamic aeroelastic stability of T-tails is dependent on the steady aerodynamic forces at aircraft trim condition. Accounting for this dependency in the flutter solution process involves correction methods for doublet lattice method (DLM) unsteady aerodynamics, enhanced DLM algorithms, unsteady vortex lattice methods (UVLM), or the use of CFD. However, the aerodynamic improvements along with a commonly applied modal approach with linear displacements results in spurious stiffness terms, which distort the flutter velocity prediction. Hence, a higher order structural approach with quadratic mode shape components is required for accurate flutter velocity prediction of T-tails. For the study of the effects of quadratic mode shape components on T-tail flutter, a generic tail configuration without sweep and taper is used. Euler based CFD simulations are applied involving a linearized frequency domain (LFD) approach to determine the generalized aerodynamic forces. These forces are obtained based on steady CFD computations at varying horizontal tail plane (HTP) incidence angles. The quadratic mode shape components of the fundamental structural modes for the vertical tail plane (VTP), i.e., out-of-plane bending and torsion, are received from nonlinear as well as linear finite element analyses. Modal coupling resulting solely from the extended modal representation of the structure and its influence on T-tail flutter is studied. The g-method is applied to solve for the flutter velocities and corresponding flutter mode shapes. The impact of the quadratic mode shape components is visualized in terms of flutter velocities in dependency of the HTP incidence angle and the static aerodynamic HTP loading.

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Flutter simulations of a T‐tail configuration using non‐linear aerodynamics

Cited by 7 publications

References 15 publications

Aircraft T-tail flutter predictions using computational fluid dynamics

Aircraft T-tail flutter predictions using computational fluid dynamics

Influence of Fluid Viscosity and Compressibility on Nonlinearities in Generalized Aerodynamic Forces for T-Tail Flutter

T-tail flutter simulations with regard to quadratic mode shape components

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