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Nonlinear Interactions in Rotordynamics: Numerical and Experimental Investigations of Internal Resonances / MEHMET AKAY

Swansea University Author: MEHMET AKAY

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DOI (Published version): 10.23889/SUThesis.71787

Abstract

In rotating machinery, tighter tolerances are crucial for efficiency, making rotor-stator interaction a key research area. This thesis explores the diverse nonlinear responses of rotordynamic systems, focusing on quasiperiodic internal resonances (IRs) in rotor-stator interactions through numerical an...

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Published: Swansea 2025
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
Supervisor: Shaw, A., and Friswell, M.
URI: https://cronfa.swan.ac.uk/Record/cronfa71787
first_indexed 2026-04-23T11:14:18Z
last_indexed 2026-04-24T07:12:30Z
id cronfa71787
recordtype RisThesis
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spelling 2026-04-23T12:19:56.5825804 v2 71787 2026-04-23 Nonlinear Interactions in Rotordynamics: Numerical and Experimental Investigations of Internal Resonances b1366490e021f33010551e3d84333829 MEHMET AKAY MEHMET AKAY true false 2026-04-23 In rotating machinery, tighter tolerances are crucial for efficiency, making rotor-stator interaction a key research area. This thesis explores the diverse nonlinear responses of rotordynamic systems, focusing on quasiperiodic internal resonances (IRs) in rotor-stator interactions through numerical and experimental analysis. Numerical continuation and time simulations were utilized on a nondimensional 2-degree-of-freedom (2-dof) gyroscopic model where a cubic stiffness was employed, as well as a hyperbolic tangent (tanh) con-tact model that approximates discontinuous contact. A novel quasiperiodic continuation method was introduced, demonstrating that periodic continuation methods can be ex-tended to include nonautonomous quasiperiodic responses which included an adaptation of the Floquet theory. Nonlinear normal modes (NNMs) was also applied to study forward (FW) and backward (BW) mode coupling.Key findings from theoretical studies indicate that IRs of frequency ratio 2:1 and 3:1 can arise even with soft nonlinearities, with damping playing a crucial role in their persistence and amplitude. Homotopy method used to switch the bifurcation diagram between different nonlinearities facilitated bifurcation analysis without prior knowledge. Experimental validation was conducted using a test rig designed to reflect the theoretical model.Experimental results confirmed the influence of damping, while additional bifurcations were attributed to real-world boundary conditions. The transition from FW and BW precession of IRs was observed in both simulations and experiments, which was termed stagnation at the point where this occurs. However, the IRs of coupling between the swinging and rotational modes were not achieved experimentally due to small basins of attraction. The use of continuation in various forms proved valuable for the analysis of the nonlinear rotating machinery.This work advances the understanding of nonlinear rotor-stator dynamics by providing new methods for analysing and classifying IRs, while generating several future work ideas.The findings have implications for designing more robust rotating machinery, considering both numerical predictions and experimental constraints. E-Thesis Swansea rotordynamics, bifurcation, continuation, internal resonance, homotopy, nonlinearnormal modes 24 10 2025 2025-10-24 10.23889/SUThesis.71787 COLLEGE NANME COLLEGE CODE Swansea University Shaw, A., and Friswell, M. Doctoral Ph.D National Ministry of Education of Türkiye National Ministry of Education of Türkiye 2026-04-23T12:19:56.5825804 2026-04-23T12:03:20.3556654 Faculty of Science and Engineering School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Aerospace Engineering MEHMET AKAY 1 71787__36571__0df444957ba448ff93d943b19dec0c1b.pdf 2025_Akay_M.final.71787.pdf 2026-04-23T12:13:02.7326579 Output 70306983 application/pdf E-Thesis – open access true Copyright: the author, Mehmet Selim Akay, 2025. Distributed under the terms of a Creative Commons Attribution-NoDerivatives 4.0 License (CC BY-NC 4.0) true eng https://creativecommons.org/licenses/by-nd/4.0/
title Nonlinear Interactions in Rotordynamics: Numerical and Experimental Investigations of Internal Resonances
spellingShingle Nonlinear Interactions in Rotordynamics: Numerical and Experimental Investigations of Internal Resonances
MEHMET AKAY
title_short Nonlinear Interactions in Rotordynamics: Numerical and Experimental Investigations of Internal Resonances
title_full Nonlinear Interactions in Rotordynamics: Numerical and Experimental Investigations of Internal Resonances
title_fullStr Nonlinear Interactions in Rotordynamics: Numerical and Experimental Investigations of Internal Resonances
title_full_unstemmed Nonlinear Interactions in Rotordynamics: Numerical and Experimental Investigations of Internal Resonances
title_sort Nonlinear Interactions in Rotordynamics: Numerical and Experimental Investigations of Internal Resonances
author_id_str_mv b1366490e021f33010551e3d84333829
author_id_fullname_str_mv b1366490e021f33010551e3d84333829_***_MEHMET AKAY
author MEHMET AKAY
author2 MEHMET AKAY
format E-Thesis
publishDate 2025
institution Swansea University
doi_str_mv 10.23889/SUThesis.71787
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Aerospace Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Aerospace Engineering
document_store_str 1
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description In rotating machinery, tighter tolerances are crucial for efficiency, making rotor-stator interaction a key research area. This thesis explores the diverse nonlinear responses of rotordynamic systems, focusing on quasiperiodic internal resonances (IRs) in rotor-stator interactions through numerical and experimental analysis. Numerical continuation and time simulations were utilized on a nondimensional 2-degree-of-freedom (2-dof) gyroscopic model where a cubic stiffness was employed, as well as a hyperbolic tangent (tanh) con-tact model that approximates discontinuous contact. A novel quasiperiodic continuation method was introduced, demonstrating that periodic continuation methods can be ex-tended to include nonautonomous quasiperiodic responses which included an adaptation of the Floquet theory. Nonlinear normal modes (NNMs) was also applied to study forward (FW) and backward (BW) mode coupling.Key findings from theoretical studies indicate that IRs of frequency ratio 2:1 and 3:1 can arise even with soft nonlinearities, with damping playing a crucial role in their persistence and amplitude. Homotopy method used to switch the bifurcation diagram between different nonlinearities facilitated bifurcation analysis without prior knowledge. Experimental validation was conducted using a test rig designed to reflect the theoretical model.Experimental results confirmed the influence of damping, while additional bifurcations were attributed to real-world boundary conditions. The transition from FW and BW precession of IRs was observed in both simulations and experiments, which was termed stagnation at the point where this occurs. However, the IRs of coupling between the swinging and rotational modes were not achieved experimentally due to small basins of attraction. The use of continuation in various forms proved valuable for the analysis of the nonlinear rotating machinery.This work advances the understanding of nonlinear rotor-stator dynamics by providing new methods for analysing and classifying IRs, while generating several future work ideas.The findings have implications for designing more robust rotating machinery, considering both numerical predictions and experimental constraints.
published_date 2025-10-24T06:30:10Z
_version_ 1865140520210137088
score 11.104773

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