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Finn, Joshua (2025) Vibrational response of complex structures to high-frequency correlated loads. PhD thesis, University of Nottingham.

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Abstract

Distributed Electric Propulsion (DEP) is an innovative aircraft concept where thrust is generated by an array of electrically powered propellers. The application of electric propulsion systems ensures that a significant proportion of the cabin noise within DEP aircraft is the result of structural vibrations driven by Turbulent Boundary Layer (TBL) effects. The purpose of this thesis is thus to extend the Dynamical Energy Analysis (DEA) approach to consider excitations by high frequency correlated pressure fields, such as the TBL pressure field.

In Chapter 1 of this thesis, the rationale of the project is expressed and the necessity for a high-frequency vibrational modelling approach is explored.

In Chapter 2, several high-frequency modelling approaches are evaluated, and the advantages of the DEA approach are highlighted. A detailed review of the DEA methodology then follows. Several TBL pressure field models are then evaluated, based upon their suitability for implementation within DEA.

In Chapter 3, the approach for modelling correlated pressure fields within DEA is developed. This is first applied to model the excitation of small structural regions by homogeneous pressure fields, before being extended to consider full body excitations. Following this, the vibrational behaviour of flat plates is considered under TBL pressure fields for various material, boundary, and flow conditions. Here, the plate response is found to be highly spatially variant and extremely dependent on the system conditions which has received minimal attention in prior studies.

In Chapter 4 the implementation of correlated point-forces, representing vibrations originating from the DEP propeller array, within DEA is explored. Here, the observed vibrational response is found to be the sum of the individual contributions plus a spatially oscillating interference term. This results in complex interference patterns, which are highly variable under different source arrangements. It is also demonstrated that in some situations these interference effects generate steerable beams of vibrational energy, which may be beneficial for sound and wear reduction. The implemented approach however leads to non-physical negative phase-space densities, and an approach to rectify this using the Husimi Density Function (HDF) is discussed.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Tanner, Gregor Richter, Martin
Keywords:	Distributed Electric Propulsion, Dynamical Energy Analysis, compuational modelling, vibrations
Subjects:	Q Science > QA Mathematics > QA801 Analytic mechanics T Technology > TL Motor vehicles. Aeronautics. Astronautics
Faculties/Schools:	UK Campuses > Faculty of Science > School of Mathematical Sciences
Item ID:	80432
Depositing User:	Finn, Joshua
Date Deposited:	30 Jul 2025 04:40
Last Modified:	30 Jul 2025 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/80432

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