Slam Simulations: An Application of Computational Fluid Dynamics

Gallagher, Paul (1985) Slam Simulations: An Application of Computational Fluid Dynamics. PhD thesis, University of Glasgow.

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The ability of ships and other marine vehicles to maintain forward speed in heavy weather is often limited by the phenomenon of slamming. The hydrodynamics of this impact problem are poorly understood in a quantative sense, though previous research has identified various physical mechanisms important to ship slamming. This thesis describes the development of a number of numerical tools designed to study the non-linear free surface flow problems caused by slamming. The research focused on two major areas of study. Firstly, a generalised simulation method for the solution of the mass and momentum conservation equations over a fluid domain bounded by a free surface and containing dynamic boundaries was developed. This technique was used to study the hydrodynamic impact of an arbitrary shaped body. A finite difference time marching solution to the continuity coupled Navier Stokes equations was employed as the basis of the simulation technique. A novel application of the well known source distribution method was used to model moving solid boundaries of arbitrary shape within the confines of the regular finite difference mesh. This particular aspect of the research allowed a marriage of traditional hydrodynamic theory and the more recent developments in computational fluid dynamics. The second area of study examined the behaviour of the compressible air layer formed between the free surface and an approaching bluff body. Again, the techniques of computational fluid dynamics were employed to solve the equations of mass and momentum conservation in the air layer and the associated free surface motions caused by the build up of pressure beneath the falling body. The thesis presents a number of computational examples in order to illustrate the development and final levels of accuracy achieved by the two classes of numerical algorithm mentioned above. Simulations of steady viscous free surface flow, wavemaker modelling, vehicle motions and added mass computations are employed to test the numerical algorithms. Results from hydrodynamic impact simulations are presented and compared with existing numerical and experimental data, for a range of hull shapes. The effects of air entrapment on impact geometry is discussed via a comparison of results obtained by the present method and data from both computations and experiment reported in the open literature. Conclusions concerning the quantitative importance of the various physical parameters involved in slamming on the ship scale are presented at the end of the thesis.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Naval engineering, Fluid mechanics
Date of Award: 1985
Depositing User: Enlighten Team
Unique ID: glathesis:1985-77344
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jan 2020 09:11
Last Modified: 14 Jan 2020 09:11

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