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Numerical modelling of hydrofoil fluid-structure interaction

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Hutchison, SR (2012) Numerical modelling of hydrofoil fluid-structure interaction. PhD thesis, University of Tasmania.

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Abstract

Marine propellers operate in unsteady non-uniform wake regions generated by the hull
and control surfaces subjecting the propeller to unsteady loading. Hydroelastic tailoring
of propeller blades is a method to reduce unsteady loading as a propeller blade passes
through a wake decit. This project seeks to gain greater insight into the eect of hy-
droelastic tailoring on a propeller by simplifying the problem into a single hydrofoil with
a sinusoidal pitch oscillation. In this study, a hydrofoil with a NACA 0009 section and
a trapezoidal planform area was used to investigate bending hydroelastic eects numeri-
cally using
uid-structure interaction modelling. The complexity of the numerical model
was varied in a systematic manner, starting with a two-dimensional foil through to a
three-dimensional two-way coupled
uid-structure interaction simulation. The commer-
cial package ANSYS was used with CFX for computational
uid dynamics and ANSYS
mechanical for the structural simulation.
In this study ANSYS was demonstrated to be a suitable tool to simulate
uid-structure
interaction in the case of an oscillating hydrofoil in pure pitch. The computational

uid dynamics results were validated in two-dimensions using NACA 0012 and 0015
sections for both static and dynamic cases using published experimental results. In
three-dimensions, stainless steel and aluminium, were investigated in addition to the rigid
(uncoupled) case. This study varies independent parameters including Reynolds number,
reduced frequency, amplitude of pitch oscillation and the mean incidence controlling the
hydrofoil response.
Comparison of static one-way and two-way coupled results shows that there are small
but apparent dierences between predicted bending deformations. However, bending de-
formations were shown to virtually have no eect on forces and moments, at least up to
moderate incidences. Rigid three-dimensional lift and moment predictions show similar
behaviour to both the two-dimensional unsteady viscous predictions and classical linear
inviscid theory for cases of zero mean incidence. In particular, lift and moment vary
linearly with amplitude of oscillation for all reduced frequencies. The lift and moment
amplitude minima occur at reduced frequencies of about 0.6 and 0.7 respectively for
both two and three-dimensional predictions; However, in the three-dimensional case the
amplitudes, relative to the lift and moment at static incidence are reduced. For a four
degrees mean incidence, the amplitudes of the lift and moment minima are signicantly
reduced for two and three-dimensional predictions compared with the zero degree mean
incidence case. Above a reduced frequency of one, for four degrees mean incidence, the
rigid three-dimensional lift and moment amplitude predictions no longer vary linearly
with incidence amplitude. The dynamic coupled analysis typically showed bending de-
formations to be similar to those for static predictions at a zero mean incidence but to be
reduced for a four degrees mean incidence at maximum incidence. Lift and moment for
the dynamic coupled cases are only slightly in
uenced for reduced frequencies less than
one depending on material properties and Reynolds number. For a reduced frequency
greater than one the lift and moment show a slight increase and vary non-linearly with
the incidence amplitude.

Item Type: Thesis (PhD)
Keywords: hydroelasticy, propellers, ocillating hydrofoil, CFD, fluid-structure interaction
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Date Deposited: 17 Aug 2012 04:39
Last Modified: 11 Mar 2016 05:53
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