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

Schäfer, Dominik (2022) Influence of Fluid Viscosity and Compressibility on Nonlinearities in Generalized Aerodynamic Forces for T-tail Flutter. In: 19th International Forum on Aeroelasticity and Structural Dynamics, IFASD 2022. International Forum on Aeroelasticity and Structural Dynamics (IFASD) 2022, 13.-17. Jun. 2022, Madrid, Spanien. ISBN 978-840942353-8.

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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-ofplane 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 amplitudedependent 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.

Item URL in elib:https://elib.dlr.de/194390/
Document Type:Conference or Workshop Item (Speech)
Title:Influence of Fluid Viscosity and Compressibility on Nonlinearities in Generalized Aerodynamic Forces for T-tail Flutter
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Schäfer, DominikUNSPECIFIEDhttps://orcid.org/0000-0002-2042-7525UNSPECIFIED
Date:June 2022
Journal or Publication Title:19th International Forum on Aeroelasticity and Structural Dynamics, IFASD 2022
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:No
Keywords:Aeroelasticity, T-tail flutter, quadratic mode shape components, CFD unsteady aerodynamics, nonlinear dynamics
Event Title:International Forum on Aeroelasticity and Structural Dynamics (IFASD) 2022
Event Location:Madrid, Spanien
Event Type:international Conference
Event Dates:13.-17. Jun. 2022
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Efficient Vehicle
DLR - Research area:Aeronautics
DLR - Program:L EV - Efficient Vehicle
DLR - Research theme (Project):L - Digital Technologies
Location: Göttingen
Institutes and Institutions:Institute of Aeroelasticity > Aeroelastic Simulation
Deposited By: Schäfer, Dominik
Deposited On:21 Mar 2023 15:55
Last Modified:18 Aug 2023 11:47

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