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Groenenboom P.H.L.,ESI Group Netherlands | Cartwright B.K.,Pacific Engineering Systems International Pty Ltd.
Journal of Hydraulic Research | Year: 2010

In this contribution the coupling of the Smoothed Particle Hydrodynamics (SPH) method for fluid dynamics to Finite Elements (FE) for structures is discussed. The accuracy of the SPH method for hydrodynamics will be demonstrated by the case of a dam break in a container in which it will be made plausible that the experimentally observed free surface profile is influenced by a wet floor. The application of the coupled SPH-FE method to fluid-structure interaction is proven by the simulation of the drop of a flexible cylinder in water. A novel approach to generate free surface waves in an arbitrary domain and validation for second-order Stokes' waves will be presented. Practical application of the methodology will be demonstrated by a study on waves inside flooded docks of an Amphibious Transport Ship and by the drop of a large canister into waves. © 2010 International Association of Hydraulic Engineering and Research. Source

Mulcahy N.L.,Pacific Engineering Systems International Pty Ltd. | Mulcahy N.L.,University of New South Wales | Prusty B.G.,University of New South Wales | Gardiner C.P.,Defence Science and Technology Organisation, Australia
Ships and Offshore Structures | Year: 2010

This paper describes and demonstrates a method for the hydroelastic tailoring of flexible composite marine propeller blades. This method is applicable to situations in which the propeller's shape adapts to changing flow conditions due to its rotation in a spatially varying wake, resulting in improved efficiency when compared to a rigid propeller. The unloaded shape of the flexible propeller and the composite lay-up are determined using an optimisation procedure. Design calculations for an example propeller revealed an improvement in the performance over a range of operating conditions. However, this may have been greater if, first, the geometry of the rigid propeller that was the basis of the flexible propeller was optimised so that it was more suited to take advantage of the hydroelastic tailoring, and second, composite materials were selected to maximise flexibility within the strength requirements. Also, a closed-form expression was developed for estimating the efficiency gain of a flexible propeller at the design condition in a spatially varying wake flow. The potential benefit of a flexible propeller is that it broadens the efficiency curve and reduces the sensitivity of the losses usually manifested in the spatially varying wake flow. © Crown Copyright 2010. Source

Kindervater C.,German Aerospace Center | Thomson R.,Cooperative Research Center for Advanced Composite Structures | Thomson R.,Advanced Composite Structures Australia Pty Ltd | Johnson A.,German Aerospace Center | And 10 more authors.
Annual Forum Proceedings - AHS International | Year: 2011

Modern helicopters make extensive use of composite materials to reduce structural weight. These include in-crash energy absorption devices integrated into the subfloor. Despite significant advances in computer-based design tools, the design of a composite energy absorbing structure is normally performed by semi-empirical methods supported by extensive testing. This paper describes the results of a project to develop improved methods for the design of composite energy absorbing structures. A building block approach was used in which, as specimens of increasing complexity were tested, simulation methods were developed and validated. These tests ranged from material characterisation through to large scale crash testing. Final validation of the simulation methods through the design and test of a representative helicopter frame section is described in detail. The results showed that the methods can be used to design a complex composite energy absorbing structure, and that they have the potential to enable improved designs, while significantly reducing physical testing requirements. Copyright © 2011 by the American Helicopter Society International, Inc. All rights reserved. Source

Mulcahy N.L.,Pacific Engineering Systems International Pty Ltd. | Prusty B.G.,University of New South Wales | Gardiner C.P.,Defence Science and Technology Organisation, Australia
Transactions of the Royal Institution of Naval Architects Part B: International Journal of Small Craft Technology | Year: 2011

A method for the hydroelastic design of flexible composite shape-adaptive hydrofoils and marine propeller blades is described and demonstrated. It is applicable to situations in which the component is to adapt its shape to small changes in flow relative to a mean operating condition. The shape-adaptive behaviour of the flexible component results in improved efficiency in comparison to a similar rigid component. Starting from a rigid component, the effect of flexibility is considered so that the component will deform in a desired manner under hydrodynamic load changes. An optimisation procedure is used to iteratively determine the composite lay-up and unloaded shape of the flexible component so that it will achieve the required deformations consistent with the calculated change in performance due to flexibility. The method is demonstrated through two examples, which both highlight the importance of the initial geometry and materials on the overall flexibility that can be achieved. © 2011 The Royal Institution of Naval Architects. Source

Croaker P.J.,Pacific Engineering Systems International Pty Ltd. | El-Khaldi F.,ESI Group | Groenenboom P.H.L.,ESI Group Netherlands | Cartwright B.K.,Pacific Engineering Systems International Pty Ltd. | Kamoulakos A.,ESI Group
MARINE 2011 - Computational Methods in Marine Engineering IV | Year: 2011

An explicit Finite Element (FE) software package with an embedded and fully coupled Smoothed Particle Hydrodynamics (SPH) solver is used to investigate the dynamic response of a floating (moored) offshore platform subject to strong wave action. The water is modelled using SPH while the platform and anchor cables are modelled using FE. The main body of the platform is modelled as a rigid body with appropriate mass, centre of gravity and moments of inertia. Coupling between the SPH and FE is automatically handled by contact algorithms available in the solver 1. To represent the effect of the mooring system on the dynamic response of the platform, the anchor cables are modelled using flexible 1-dimensional (1D) finite elements. The stable time step for these 1D elements is much smaller than for the SPH particles and including the flexible anchor cables in the model would ordinarily cause excessive simulation times. However, a technique known as multi-model coupling is used to partition the analysis model into 2 separate models, each of which advances at its own stable time step 2. This technique is shown to result in a total simulation time that is comparable to that obtained when running the case without anchor cables. The use of periodic boundary conditions applied to the SPH particles allowed the computational domain to be limited to 4 wavelengths in the direction of wave travel. The waves are generated by applying the moving floor technique 3. The dynamic response of the platform is presented for the case when the platform is operating at a depth of 310 m under the influence of waves with a wavelength of 365 m and amplitude of 7.8 m. This represents the survival condition for a reference semi-submersible platform. An extension of this approach considering the stresses induced in structural members of the platforms is also demonstrated by replacing the rigid representation of the cranes with flexible finite elements. Source

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