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A Coupled Newton–Krylov Time Spectral Solver for Flutter Prediction

TitleA Coupled Newton–Krylov Time Spectral Solver for Flutter Prediction
Publication TypeConference Papers
Year of Publication2018
AuthorsHe, S, Jonsson, E, Mader, CA, Martins, JRRA
Conference Name2018 AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
Conference LocationKissimmee, FL
Keywordsflutter, time-spectral

Flutter methods can be broadly categorized into low and high fidelity methods. Low fidelity methods in general lack the ability to capture accurately the strong nonlinearities in the transonic flow regime; researchers have used Harmonic Balance (HB) method (a frequency domain method equivalent with time-spectral (TS) method modeled in time domain) to capture the flutter onset point. However, the previous solution method is hindered by scalability: O(NCSD) CFD evaluations needed for each Newton step, and a lack of robustness due to the nature of Newton–Raphson method. In this paper, we propose a preconditioned coupled Jacobian-free Newton–Krylov (CNK) method for TS flutter equations. By resolving the coupled system directly, the O(NCSD) CFD evaluations are avoided. With a line search method CNK is expected to be more robust. A block-Jacobian preconditioning method is used in this work. CNK is compared with and validated by time-accurate (TA) flutter boundary results from both literature and our new implementation.

Citation KeyHe2018